THE BLOOD
Preliminary Considerations.--The blood consists of a fluid of
complicated and variable composition, the plasma, in which are
suspended great numbers of microscopic structures: viz., red
corpuscles, white corpuscles, blood-platelets, and blood-dust.
_Red corpuscles_, or _erythrocytes_, are biconcave discs, red when
viewed by reflected light or in thick layer, and straw-colored when
viewed by transmitted light or in thin layer. They give the blood its
red color. They are cells which have been highly differentiated for
the purpose of carrying oxygen from the lungs to the tissues. This is
accomplished by means of an iron-bearing proteid, hemoglobin, which
they contain. In the lungs hemoglobin forms a loose combination with
oxygen, which it readily gives up when it reaches the tissues. Normal
erythrocytes do not contain nuclei. They are formed from preëxisting
nucleated cells in the bone-marrow.
_White corpuscles_, or _leukocytes_, are less highly differentiated
cells. There are several varieties. They all contain nuclei, and most
of them contain granules which vary in size and staining properties.
They are formed in the bone-marrow and lymphoid tissues.
_Blood-platelets_, or _blood-plaques_, are colorless or slightly
bluish, spheric or ovoid bodies, about one-third or one-half the
diameter of an erythrocyte. Their structure, nature, and origin have
not been definitely determined.
{140} The _blood-dust of Müller_ consists of fine granules which have
vibratory motion. Little is known of them. It has been suggested that
they are granules from disintegrated leukocytes.
_Coagulation_ consists essentially in the transformation of
fibrinogen, one of the proteins of the blood, into fibrin by means of
a ferment derived from disintegration of the leukocytes. The resulting
coagulum is made up of a meshwork of fibrin fibrils with entangled
corpuscles and plaques. The clear, straw-colored fluid which is left
after separation of the coagulum is called _blood-serum_. Normally,
coagulation takes place in two to eight minutes after the blood leaves
the vessels. It is frequently desirable to determine the coagulation
time. The simplest method is to place a drop of blood upon a perfectly
clean slide, and to draw a needle through it at half-minute intervals.
When the clot is dragged along by the needle, coagulation has taken
place. This method is probably sufficient for ordinary clinical work.
For very accurate results the method of Russell and Brodie, for which
the reader is referred to the larger text-books, is recommended.
Coagulation is notably delayed in hemophilia and icterus and after
administration of citric acid. It is hastened by administration of
calcium chlorid.
For most clinical examinations only one drop of blood is required.
This may be obtained from the lobe of the ear, the palmar surface of
the tip of the finger, or, in the case of infants, the plantar surface
of the great toe. With nervous children the lobe of the ear is
preferable, as it prevents their seeing what is being done. An
edematous or congested part should be avoided. The site should be well
rubbed with alcohol to remove dirt and epithelial {141} débris and to
increase the amount of blood in the part. After allowing sufficient
time for the circulation to equalize, the skin is punctured with a
blood lancet (of which there are several patterns upon the market) or
some substitute, as a Hagedorn needle, aspirating needle, trocar, or a
pen with one of its nibs broken off. Nothing is more unsatisfactory
than an ordinary sewing-needle. The lancet should be cleaned with
alcohol before and after using, but need not be sterilized. If the
puncture be made with a _firm, quick stroke_, it is practically
painless. The first drop of blood which appears should be wiped away,
and the second used for examination. The blood should not be pressed
out, since this dilutes it with serum from the tissues; but moderate
pressure some distance above the puncture is allowable.
[Illustration: FIG. 64.--Daland's blood-lancet.]
When a larger amount of blood is required, it may be obtained with a
sterile hypodermic syringe from one of the veins at the elbow.
Clinical study of the blood may be discussed under the following
heads: I. Hemoglobin. II. Enumeration of erythrocytes. III. Color
index. IV. Enumeration of leukocytes. V. Enumeration of plaques. VI.
Study of stained blood. VII. Blood parasites. VIII. Serum reactions.
IX. Tests for recognition of blood. X. Special blood pathology.
{142} I. HEMOGLOBIN
Hemoglobin is an iron-bearing proteid. It is found only within the red
corpuscles, and constitutes about 90 per cent. of their weight. The
actual amount of hemoglobin is never estimated clinically: it is the
relation which the amount present bears to the normal which is
determined. Thus the expression, "50 per cent. hemoglobin," when used
clinically, means that the blood contains 50 per cent. of the normal.
Theoretically, the normal would be 100 per cent., but with the methods
of estimation in general use the blood of healthy persons ranges from
85 to 105 per cent.; these figures may, therefore, be taken as normal.
_Increase of hemoglobin_, or _hyperchromemia_, is uncommon, and is
probably more apparent than real. It accompanies an increase in number
of erythrocytes, and may be noted in change of residence from a lower
to a higher altitude; in poorly compensated heart disease with
cyanosis; in concentration of the blood from any cause, as the severe
diarrhea of cholera; and in "idiopathic polycythemia."
_Decrease of hemoglobin_, or _oligochromemia_, is very common and
important. It is the most striking feature of the secondary anemias
(p. 204). Here the hemoglobin loss may be slight or very great. In
mild cases a slight decrease of hemoglobin is the only blood change
noted. In very severe cases, especially in repeated hemorrhages,
malignant disease, and infection by the worms uncinaria and
bothriocephalus latus, hemoglobin may fall to 15 per cent. Hemoglobin
is always diminished, and usually very greatly, in chlorosis,
pernicious anemia, and leukemia.
{143} _Estimation of Hemoglobin_.--There are many methods, but none is
entirely satisfactory. Those which are most widely used are here
described.
* * * * *
[Illustration: FIG. 65.--Von Fleischl's hemoglobinometer: _a_, Stand;
_b_, narrow wedge-shaped piece of colored glass fitted into a frame
(_c_), which passes under the chamber; _d_, hollow metal cylinder,
divided into two compartments, which holds the blood and water; _e_,
plaster-of-Paris plate from which the light is reflected through the
chamber; _f_, screw by which the frame containing the graduated
colored glass is moved; _g_, capillary tube to collect the blood; _h_,
pipet for adding the water; _i_, opening through which may be seen the
scale indicating percentage of hemoglobin.]
(1) Von Fleischl Method.--The apparatus consists of a stand somewhat
like the base and stage of a microscope (Fig. 65). Under the stage is
a movable bar of colored glass, shading from pale pink at one end to
deep red at the other. The frame in which this bar is held is marked
with a scale of hemoglobin percentages corresponding to the different
shades of red. By means of a rack and pinion, the color-bar can be
moved from end to end beneath a round opening in the center of the
stage. A small metal cylinder, which has a glass bottom and which is
divided vertically into two equal compartments, can be placed over the
opening in the stage so that one of its {144} compartments lies
directly over the color-bar. Accompanying the instrument are a number
of short capillary tubes in metal handles.
Having punctured the finger-tip or lobe of the ear as already
described, wipe off the first drop of blood, and from the second fill
one of the capillary tubes. Hold the tube horizontally, and touch its
tip to the drop of blood, which will readily flow into it if it be
clean and dry. Avoid getting any blood upon its outer surface. With a
medicine-dropper, rinse the blood from the tube into one of the
compartments of the cylinder, using distilled water, and mix well.
Fill both compartments level full with distilled water, and place the
cylinder over the opening in the stage so that the compartment which
contains only water lies directly over the bar of colored glass.
In a dark room, with the light from a candle reflected up through the
cylinder, move the color-bar along with a jerking motion until both
compartments have the same depth of color. The number upon the scale
corresponding to the portion of the color-bar which is now under the
cylinder gives the percentage of hemoglobin. While comparing the two
colors, place the instrument so that they will fall upon the right and
left halves of the retina, rather than upon the upper and lower
halves; and protect the eye from the light with a cylinder of paper or
pasteboard. After use, clean the metal cylinder with water, and wash
the capillary tube with water, alcohol, and ether, successively.
Results with this instrument are accurate to within about 5 per cent.
A recent modification of the von Fleischl apparatus by Miescher gives
an error which need not exceed 1 per cent. It is, however, better
adapted to laboratory use than to the needs of the practitioner.
(2) The Sahli hemoglobinometer (Fig. 66) is an improved form of the
well known Gowers instrument. It consists of a hermetically sealed
comparison tube containing a 1 per cent. solution of acid hematin, a
graduated test-tube of the same {145} diameter, and a pipet of 20
c.mm. capacity. The two tubes are held in a black frame with a white
ground-glass back.
[Illustration: FIG. 66.--Sahli's hemoglobinometer.]
Place a few drops of decinormal hydrochloric acid solution in the
graduated tube. Obtain a drop of blood and draw it into the pipet to
the 20 c.mm. mark. Wipe off the tip of the pipet, blow its contents
into the hydrochloric acid solution in the tube, and rinse well. In a
few minutes the hemoglobin is changed to acid hematin. Place the two
tubes in the compartments of the frame, and dilute the fluid with
water drop by drop, mixing after each addition, until it has exactly
the same color as the comparison tube. The graduation corresponding to
the surface of the fluid then indicates the {146} percentage of
hemoglobin. Decinormal hydrochloric acid solution may be prepared with
sufficient accuracy for this purpose by adding 15 c.c. of the
concentrated acid to 985 c.c. distilled water. A little chloroform
should be added as a preservative.
This method is very satisfactory in practice, and is accurate to
within 5 per cent. The comparison tube is said to keep its color
indefinitely, but, unfortunately, not all the instruments upon the
market are well standardized.
(3) Dare's hemoglobinometer (Fig. 67) differs from the others in using
undiluted blood. The blood is allowed to flow by capillarity into the
slit between two small plates of glass. It is then placed in the
instrument and compared with different portions of a circular disc of
colored glass. The reading must be made quickly, before clotting takes
place. This instrument is easy to use, and is one of the most
accurate.
[Illustration: FIG. 67.--Dare's hemoglobinometer.]
(4) Hammerschlag Method.--This is an indirect method which depends
upon the fact that the percentage of hemoglobin varies directly with
the specific gravity of the blood. It yields fairly accurate results
except in leukemia, where the large number of leukocytes disturbs the
relation.
Mix chloroform and benzol in a urinometer tube so that {147} the
specific gravity of the mixture is near the probable specific gravity
of the blood. Add a drop of blood by means of a pipet of small
caliber. If the drop floats near the surface, add a little benzol; if
it sinks to the bottom, add a little chloroform. When it remains
stationary near the middle, the mixture has the same specific gravity
as the blood. Take the specific gravity with a urinometer, and obtain
the corresponding percentage of hemoglobin from the following table:
SPECIFIC HEMOGLOBIN SPECIFIC HEMOGLOBIN
GRAVITY. PER CENT. GRAVITY. PER CENT.
1.033-1.035 25-30 1.048-1.050 55-65
1.035-1.038 30-35 1.050-1.053 65-70
1.038-1.040 35-40 1.053-1.055 70-75
1.040-1.045 40-45 1.055-1.057 75-85
1.045-1.048 45-55 1.057-1.060 85-95
For accurate results with this method, care and patience are demanded.
The following precautions must be observed:
(_a_) The two fluids must be well mixed after each addition of
chloroform or benzol. Close the tube with the thumb and invert several
times. Should this cause the drop of blood to break up into very small
ones, adjust the specific gravity as accurately as possible with
these, and test it with a fresh drop.
(_b_) The drop of blood must not be too large; it must not contain an
air-bubble, it must not adhere to the side of the tube, and it must
not remain long in the fluid.
(_c_) The urinometer must be standardized for the chloroform-benzol
mixture. Most urinometers give a reading two or three degrees too
high, owing to the low surface tension. Make a mixture such that a
drop of distilled water will remain suspended in it (_i.e._, with a
specific gravity of 1.000) and correct the urinometer by this.
(5) Tallquist Method.--The popular Tallquist hemoglobinometer consists
simply of a book of small sheets of absorbent paper and a carefully
printed scale of colors (Fig. 68).
Take up a large drop of blood with the absorbent paper, {148} and when
the humid gloss is leaving, compare the stain with the color scale.
The color which it matches gives the percentage of hemoglobin. Except
in practised hands, this method is accurate only to within 10 or 20
per cent.
[Illustration: FIG. 68.--Tallquist's hemoglobin scale.]
* * * * *
Of the methods given, the physician should select the one which best
meets his needs. With any method, practice is essential to accuracy.
The von Fleischl has long been the standard instrument, but has lately
fallen into some disfavor. For accurate work the best instruments are
the von Fleischl-Miescher and the Dare. They are, however, expensive,
and it is doubtful whether they are enough more accurate than the
Sahli instrument to justify the difference in cost. The latter is
probably the most satisfactory for the practitioner, provided a {149}
well-standardized color-tube is obtained. The specific gravity method
is very useful when special instruments are not at hand. The Tallquist
scale is so inexpensive and so convenient that it should be used by
every physician at the bedside and in hurried office work; but it
should not supersede the more accurate methods.
II. ENUMERATION OF ERYTHROCYTES
In health there are about 5,000,000 red corpuscles per cubic
millimeter of blood. Normal variations are slight. The number is
generally a little less--about 4,500,000--in women.
_Increase of red corpuscles_, or _polycythemia_, is unimportant. There
is a decided increase following change of residence from a lower to a
higher altitude, averaging about 50,000 corpuscles for each 1000 feet,
but frequently much greater. The increase, however, is not permanent.
In a few months the erythrocytes return to nearly their original
number. Three views are offered in explanation: (_a_) Concentration of
the blood, owing to increased evaporation from the skin; (_b_)
stagnation of corpuscles in the peripheral vessels, because of lowered
blood-pressure; (_c_) new-formation of corpuscles, this giving a
compensatory increase of aëration surface.
Pathologically, polycythemia is uncommon. It may occur in: (_a_)
concentration of the blood from severe watery diarrhea; (_b_) chronic
heart disease, especially the congenital variety, with poor
compensation and cyanosis; and (_c_) idiopathic polycythemia, which is
considered to be an independent disease, and is characterized by
cyanosis, blood counts of 7,000,000 to 10,000,000, hemoglobin 120 to
150 per cent., and a normal number of leukocytes.
{150} _Decrease of red corpuscles_, or _oligocythemia_. Red corpuscles
and hemoglobin are commonly decreased together, although usually not
to the same extent.
Oligocythemia occurs in all but the mildest symptomatic anemias. The
blood count varies from near the normal in moderate cases down to
1,500,000 in very severe cases. There is always a decrease of red
cells in chlorosis, but it is often slight, and is relatively less
than the decrease of hemoglobin. Leukemia gives a decided
oligocythemia, the average count being about 3,000,000. The greatest
loss of red cells occurs in pernicious anemia, where counts below
1,000,000 are not uncommon.
[Illustration: FIG. 69.--Thoma-Zeiss hemocytometer: _a_, Slide used in
counting; _b_, sectional view; _d_, red pipet; _e_, white pipet.]
The most widely used and most satisfactory instrument for counting the
corpuscles is that of Thoma-Zeiss. The hematocrit is not to be
recommended for accuracy, since in anemia, where blood counts are most
important, the red cells vary greatly in size and probably also in
elasticity. {151} The hematocrit is, however, useful in determining
the relative volume of corpuscles and plasma, and seems to be gaining
in favor.
* * * * *
[Illustration: FIG. 70.--Ordinary ruling of counting chamber, showing
red corpuscles in left upper corner.]
The Thoma-Zeiss instrument consists of two pipets for diluting the
blood and a counting chamber (Fig. 69). The counting chamber is a
glass slide with a square platform in the middle. In the center of the
platform is a circular opening, in which is set a small circular disc
in such a manner that it is surrounded by a "ditch," and that its
surface is exactly one-tenth of a millimeter below the surface of the
square platform. Upon this disc is ruled a square millimeter,
subdivided into 400 small squares. Each fifth row of small squares has
double ruling for convenience in counting (Fig. 70). A thick {152}
cover-glass, ground perfectly plane, accompanies the counting chamber.
Ordinary cover-glasses are of uneven surface, and should not be used
with this instrument.
It is evident that, when the cover-glass is in place upon the
platform, there is a space exactly one-tenth of a millimeter thick
between it and the disc; and that, therefore, the square millimeter
ruled upon the disc forms the base of a space holding exactly
one-tenth of a cubic millimeter.
[Illustration: FIG. 71.--Method of drawing blood into the pipet
(Boston).]
Technic.--To count the red corpuscles, use the pipet with 101 engraved
above the bulb. It must be clean and dry. Obtain a drop of blood as
already described. Suck blood into the pipet to the mark 0.5 or 1.
Should the blood go beyond the mark, draw it back by touching the tip
of the pipet to a moistened handkerchief. Quickly wipe off the blood
adhering to the tip, plunge it into the diluting fluid, and suck the
fluid up to the mark 101, slightly rotating the pipet meanwhile. This
dilutes the blood 1:200 or 1:100, according to the amount of blood
taken. Except in cases of severe {153} anemia, a dilution of 1:200 is
preferable. Close the ends of the pipet with the fingers, and shake
vigorously until the blood and diluting fluid are well mixed.
When it is not convenient to count the corpuscles at once, place a
heavy rubber band around the pipet so as to close the ends, inserting
a small piece of rubber-cloth or other tough, non-absorbent material
if necessary to prevent the tip from punching through the rubber. It
may be kept thus for twenty-four hours or longer.
When ready to make the count, mix again thoroughly by shaking; blow
two or three drops of the fluid from the pipet, wipe off its tip, and
then place a small drop (the proper size can be learned only by
experience) upon the disc of the counting chamber. Adjust the cover
immediately. Hold it by diagonal corners above the drop of fluid so
that a third corner touches the slide and rests upon the edge of the
platform. Place a finger upon this corner, and, by raising the finger,
allow the cover to fall quickly into place. If the cover be properly
adjusted, faint concentric lines of the prismatic colors--Newton's
rings--can be seen between it and the platform when the slide is
viewed obliquely. They indicate that the two surfaces are in close
apposition. If they do not appear at once, slight pressure upon the
cover may bring them out. Failure to obtain them is usually due to
dirty slide or cover--both must be perfectly clean and free from dust.
The drop placed upon the disc must be of such size that, when the
cover is adjusted, it nearly or quite covers the disc, and that none
of it runs over into the "ditch." There should be no bubbles upon the
ruled area.
Allow the corpuscles to settle for a few minutes, and then examine
with a low power to see that they are evenly distributed. If they are
not _evenly distributed over the whole disc_, the counting chamber
must be cleaned and a new drop placed in it.
Probably the most satisfactory objective for counting is the special
one-sixth for blood work already mentioned. To {154} understand the
principle of counting, it is necessary to remember that the large
square (400 small squares) represents a capacity of one-tenth of a
cubic millimeter. Find the number of corpuscles in the large square,
multiply by 10 to find the number in 1 c.mm. of the diluted blood, and
finally, by the dilution, to find the number in 1 c.mm. of undiluted
blood. Instead of actually counting all the corpuscles, it is
customary to count those in only a limited number of small squares,
and from this to calculate the number in the large square.
In practice a convenient procedure is as follows: _With a dilution of
1:200, count the cells in 80 small squares, and to the sum add 4
ciphers; with dilution of 1:100, count 40 small squares and add 4
ciphers._ Thus, if with 1:200 dilution, 450 corpuscles were counted,
the total count would be 4,500,000 per c.mm. This method is
sufficiently accurate for all clinical purposes, provided the
corpuscles are evenly distributed and two drops from the pipet be
counted. It is convenient to count a block of 20 small squares in each
corner of the large square. It distribution be even, the difference
between the number of cells in any two such blocks should not exceed
twenty. Corpuscles which touch the upper and left sides should be
counted as if within the squares, those touching the lower and right
sides, as outside, and _vice versâ_.
_Diluting Fluids_.--The most widely used are Hayem's and Toisson's.
Both of these have high specific gravities, so that, when well mixed,
the corpuscles do not separate quickly. Toisson's fluid is probably
the better for beginners, because it is colored and can be easily seen
as it is drawn into the pipet. It stains the nuclei of leukocytes
blue, but this is no real advantage. It must be filtered frequently.
HAYEM'S FLUID. TOISSON'S FLUID.
Mercuric chlorid 0.5 Methyl-violet, 5 B 0.025
Sodium sulphate 5.0 Sodium chlorid 1.000
Sodium chlorid 1.0 Sodium sulphate 8.000
Distilled water 200.0 Glycerin 30.000
Distilled water 160.000
{155} _Sources of Error_.--The most common sources of error in making
a blood count are:
(_a_) Inaccurate dilution, either from faulty technic or inaccurately
graduated pipets. The instruments made by Zeiss can be relied upon.
(_b_) Too slow manipulation, allowing a little of the blood to
coagulate and remain in the capillary portion of the pipet.
(_c_) Inaccuracy in depth of counting chamber, which sometimes results
from softening of the cement by alcohol or heat. The slide should not
be cleaned with alcohol nor left to lie in the warm sunshine.
(_d_) Uneven distribution of the corpuscles. This results when the
blood is not thoroughly mixed with the diluting fluid, or when the
cover-glass is not applied soon enough after the drop is placed upon
the disc.
_Cleaning the Instrument_.--The instrument should be cleaned
immediately after using, and the counting chamber and cover must be
cleaned again just before use.
Draw through the pipet, successively, water, alcohol, ether, and air.
This can be done with the mouth, but it is much better to use a rubber
bulb. When the mouth is used, the moisture of the breath will condense
upon the interior of the pipet unless the fluids be shaken and not
blown out. If blood has coagulated in the pipet--which happens when
the work is done too slowly--dislodge the clot with a horse-hair, and
clean with strong sulphuric acid, or let the pipet stand over night in
a test-tube of the acid. Even if the pipet does not become clogged, it
should be occasionally cleaned in this way.
* * * * *
III. COLOR INDEX
This is an expression which indicates the amount of hemoglobin in each
red corpuscle compared with the normal amount. For example, a color
index of 1.0 indicates that each corpuscle contains the normal amount
{156} of hemoglobin; of 0.5, that each contains one-half the normal.
The color index is most significant in chlorosis and pernicious
anemia. In the former it is usually much decreased; in the latter,
generally much increased. In symptomatic anemia it is generally
moderately diminished.
* * * * *
To obtain the color index, divide the percentage of hemoglobin by the
percentage of corpuscles. The percentage of corpuscles is found by
multiplying the first two figures of the red corpuscle count by two.
This simple method holds good for all counts of 1,000,000 or more.
Thus, a count of 2,500,000 is 50 per cent. of the normal. If, then,
the hemoglobin has been estimated at 40 per cent., divide 40 (the
percentage of hemoglobin) by 50 (the percentage of corpuscles). This
gives 4/5, or 0.8, as the color index.
IV. ENUMERATION OF LEUKOCYTES
The normal number of leukocytes varies from 5000 to 10,000 per cubic
millimeter of blood. The number is larger in robust individuals than
in poorly nourished ones, and if disease be excluded, may be taken as
an index of the individual's nutrition. Since it is well to have a
definite standard, 7500 is generally adopted as the normal for the
adult. With children the number is somewhat greater, counts of 12,000
and 15,000 being common in healthy children under twelve years of age.
_Decrease in number of leukocytes_, or _leukopenia_, is not important.
It is common in persons who are poorly nourished, although not
actually sick. The infectious diseases in which leukocytosis is absent
(p. 160) often cause a slight decrease of leukocytes. Chlorosis may
{157} produce leukopenia, as also pernicious anemia, which usually
gives it in contrast to the secondary anemias, which are frequently
accompanied by leukocytosis.
_Increase in number of leukocytes_ is common and of great importance.
It may be considered under two heads: A. Increase of leukocytes due to
chemotaxis and stimulation of the blood-making organs, or
_leukocytosis_. B. Increase of leukocytes due to _leukemia_. The
former may be classed as a _transient_, the latter, as a _permanent_,
increase.
A. LEUKOCYTOSIS
This term has not acquired a definite meaning. By some it is applied
to any increase in number of leukocytes; by others, it is restricted
to increase of the polymorphonuclear neutrophilic variety. As has been
indicated, it is here taken to mean any increase in number of
leukocytes caused by chemotaxis and stimulation of the blood-producing
structures; and includes every increase of leukocytes except that due
to leukemia.
By chemotaxis is meant that property of certain agents by which they
attract or repel leukocytes--positive chemotaxis and negative
chemotaxis respectively. An excellent illustration is the accumulation
of leukocytes at the site of inflammation, owing to the positively
chemotactic influence of bacteria and their products. A great many
agents possess the power of attracting leukocytes into the general
circulation. Among these are bacteria and many organic and inorganic
poisons.
Chemotaxis alone will not explain the continuance of leukocytosis for
more than a short time. It is probable that substances which are
positively chemotactic also stimulate the blood-producing organs to
increased {158} formation of leukocytes; and in at least one form of
leukocytosis such stimulation probably plays the chief part.
In general, the response of the leukocytes to chemotaxis is a
conservative process. It is the gathering of soldiers to destroy an
invader. This is accomplished partly by means of phagocytosis--actual
ingestion of the enemy--and partly by means of chemic substances which
the leukocytes produce.
In those diseases in which leukocytosis is the rule the degree of
leukocytosis depends upon two factors: the severity of the infection
and the resistance of the individual. A well-marked leukocytosis
usually indicates good resistance. A mild degree means that the body
is not reacting well, or else that the infection is too slight to call
forth much resistance. Leukocytosis may be absent altogether when the
infection is extremely mild, or when it is so severe as to overwhelm
the organism before it can react. These facts are especially true of
pneumonia, diphtheria, and abdominal inflammations, in which
conditions the degree of leukocytosis is of considerable prognostic
value.
As will be seen later, there are several varieties of leukocytes in
normal blood, and many chemotactic agents attract only one variety and
either repel or do not influence the others. These varieties may be
divided into two general classes:
(_a_) Those having active independent ameboid motion. They are able to
migrate readily from place to place and to ingest small bodies, as
bacteria. From this latter property they derive their name of
_phagocytes_. This group includes all varieties except the
lymphocytes. The polymorphonuclear leukocytes are taken as the type of
the group, because they are by far the most numerous.
{159} (_b_) Those having very little or no independent
motion--_non-phagocytic leukocytes_. Only the lymphocytes belong to
this class.
By this classification we may distinguish two types of leukocytosis,
according to the type of cell chiefly affected: a phagocytic and a
non-phagocytic type.
1. Phagocytic Leukocytosis.--Theoretically, there should be a
subdivision of phagocytic leukocytosis for each variety of phagocyte,
_e.g._, polymorphonuclear leukocytosis, eosinophilic leukocytosis,
large mononuclear leukocytosis, etc. Practically, however, only one of
these, polymorphonuclear leukocytosis, need be considered under the
head of leukocytosis. Increase in number of the other phagocytes will
be considered at another place. They are present in the blood in such
small numbers normally that even a marked increase scarcely affects
the total leukocyte count; and, besides, substances which attract them
into the circulation frequently repel the polymorphonuclears, so that
the total number of leukocytes may actually be decreased.
Polymorphonuclear leukocytosis may be either physiologic or
pathologic. A count of 20,000 would be considered a marked
leukocytosis; of 30,000, high; above 50,000, extremely high.
(1) Physiologic Polymorphonuclear Leukocytosis.--This is never very
marked, the count rarely exceeding 15,000 per cubic millimeter. It
occurs in the new-born, in pregnancy, during digestion, and after cold
baths. There is moderate leukocytosis in the moribund state; this is
commonly classed as physiologic, but is probably due mainly to
terminal infection.
{160} (2) Pathologic Polymorphonuclear Leukocytosis.--The
classification here given follows Cabot:
(_a_) _Infectious and Inflammatory_.--The majority of infectious
diseases produce leukocytosis. The most notable exceptions are
influenza, malaria, measles, tuberculosis, except when invading the
serous cavities or when complicated by mixed infection, and typhoid
fever, in which leukocytosis indicates an inflammatory complication.
All inflammatory and suppurative diseases cause leukocytosis, except
when slight or well walled off. Appendicitis has been studied with
especial care in this connection, and the conclusions now generally
accepted probably hold good for most acute intra-abdominal
inflammations. A marked leukocytosis (20,000 or more) nearly always
indicates abscess, peritonitis, or gangrene, even though the clinical
signs be slight. Absence of or mild leukocytosis indicates a mild
process, or else an overwhelmingly severe one; and operation may
safely be postponed unless the abdominal signs are very marked. On the
other hand, no matter how low the count, an increasing
leukocytosis--counts being made hourly--indicates a spreading process
and demands operation, regardless of other symptoms.
Leukocyte counts alone are often disappointing, but are of much more
value when considered in connection with a differential count of
polymorphonuclears (see p. 181).
(_b_) _Malignant Disease_.--Leukocytosis occurs in about one-half of
the cases of malignant disease. In many instances it is probably
independent of any secondary infection, since it occurs in both
ulcerative and non-ulcerative cases. It seems to be more common in
sarcoma than in carcinoma. Very large counts are rarely noted.
{161} (_c_) _Post-hemorrhagic_.--Moderate leukocytosis follows
hemorrhage and disappears in a few days.
(_d_) _Toxic_.--This is a rather obscure class, which includes gout,
chronic nephritis, acute yellow atrophy of the liver, ptomain
poisoning, prolonged chloroform narcosis, and quinin poisoning.
Leukocytosis may or may not occur in these conditions, and is not
important.
(_e_) _Drugs_.--This also is an unimportant class. Most tonics and
stomachics and many other drugs produce a slight leukocytosis.
2. Non-phagocytic or Lymphocyte Leukocytosis.--This is characterized
by an increase in the total leukocyte count, accompanied by an
increase in the percentage of lymphocytes. The word "lymphocytosis" is
often used in the same sense. It is better, however, to use the latter
as referring to any increase in number of lymphocytes, without regard
to the total count, since an actual increase in number of lymphocytes
is frequently accompanied by a normal or subnormal leukocyte count,
owing to loss of polymorphonuclears.
Non-phagocytic leukocytosis is probably due more to stimulation of
blood-making organs than to chemotaxis. It is less common, and is
rarely so marked as a polymorphonuclear leukocytosis. When marked, the
blood cannot be distinguished from that of lymphatic leukemia.
A marked lymphocyte leukocytosis occurs in pertussis, and is of value
in diagnosis. It appears early in the catarrhal stage, and persists
until after convalescence. The average leukocyte count is about
17,000, lymphocytes predominating. There is moderate lymphocyte
leukocytosis in other diseases of childhood, as rickets, scurvy, and
especially hereditary syphilis, where the blood-picture {162} may
approach that of pertussis. It must be borne in mind in this
connection that lymphocytes are normally more abundant in the blood of
children than in that of adults.
Slight lymphocyte leukocytosis occurs in many other pathologic
conditions, but is of little significance.
B. LEUKEMIA
This is an idiopathic disease of the blood-making organs, which is
accompanied by an enormous increase in number of leukocytes. The
leukocyte count sometimes exceeds 1,000,000 per cubic millimeter, and
leukemia is always to be suspected when it exceeds 50,000. Lower
counts do not, however, exclude it. The subject is more fully
discussed later (p. 208).
The leukocytes are counted with the Thoma-Zeiss instrument, already
described. Recently, several new rulings of the disc have been
introduced, notably the Zappert and the Türk (Fig. 72), which give a
ruled area of nine square millimeters. They were devised for counting
the leukocytes in the same specimen with the red corpuscles. The red
cells are counted in the usual manner, after which all the leukocytes
in the whole area of nine square millimeters are counted; and the
number in a cubic millimeter of undiluted blood is then easily
calculated. Leukocytes are easily distinguished from red cells,
especially when Toisson's diluting fluid is used. This method may be
used with the ordinary ruling by adjusting the microscopic field to a
definite size, and counting a sufficient number of fields, as
described later. Although less convenient, it is more accurate to
count the leukocytes separately, with less dilution of the blood, as
follows:
* * * * *
{163} Technic.--A larger drop of blood is required than for counting
the erythrocytes, and more care in filling the pipet. Use the pipet
with 11 engraved above the bulb. Suck the blood to the mark 0.5 or
1.0, and the diluting fluid to the mark 11. This gives a dilution of
1:20 or 1:10, respectively. The dilution of 1:20 is easier to make.
Mix well by shaking in all directions except in the long axis of the
pipet; blow out two or three drops, place a drop in the counting
chamber, and adjust the cover as already described (p. 153).
[Illustration: FIG. 72.--Türk ruling of counting chamber.]
Examine with a low power to see that the cells are evenly distributed.
Count with the two-thirds objective and a high eye-piece, or with the
long-focus one-sixth and a low eye-piece. {164} A one-fourth objective
will be found very satisfactory for this purpose.
With the ordinary ruling of the disc, count all the leukocytes in the
large square, multiply by 10 to find the number in 1 c.mm. of diluted
blood, and by the dilution to find the number per c.mm. of undiluted
blood. In every case at least 100 leukocytes must be counted as a
basis for calculation, and it is much better to count 500. This will
necessitate examination of several drops from the pipet. With the
Zappert and Türk rulings a sufficient number can usually be counted in
one drop, but the opportunity for error is very much greater when only
one drop is examined.
[Illustration: FIG. 73.--Size of field required in counting leukocytes
as described in the text.]
In routine work the author's modification of the "circle" method is
very satisfactory: Draw out the tube of the microscope until the field
of vision has a diameter equal to eight {165} times the side of a
small square (Fig. 73). The area of this field closely approximates
one-tenth of a square millimeter. With a dilution of 1:20, count the
leukocytes in 20 such fields upon different parts of the disc without
regard to the ruled lines, and to their sum add two ciphers. With
dilution of 1:10, count 10 such fields, and add two ciphers. Thus,
with 1:10 dilution, if 150 leukocytes were counted in 10 fields, the
leukocyte count would be 15,000 per c.mm. To compensate for possible
unevenness of distribution, it is best to count a row of fields
horizontally and a row vertically across the disc. This method is
applicable to any degree of dilution of the blood, and is simple to
remember: _one always counts a number of fields equal to the number of
times the blood has been diluted, and adds two ciphers_.
It is frequently impossible to obtain the proper size of field with
the objectives and eye-pieces at hand. In such case, place a cardboard
disc with a circular opening upon the diaphragm of the eye-piece, and
adjust the size of the field by drawing out the tube. The circular
opening can be cut with a cork-borer.
_Diluting Fluids_.--The diluting fluid should dissolve the red
corpuscles so that they will not obscure the leukocytes. The simplest
fluid is a 0.5 per cent. solution of acetic acid. More satisfactory is
the following: glacial acetic acid, 1 c.c.; 1 per cent. aqueous
solution of gentian-violet, 1 c.c.; distilled water, 100 c.c. These
solutions must be filtered frequently.
* * * * *
V. ENUMERATION OF BLOOD-PLAQUES
The average normal number of plaques is variously given as 200,000 to
700,000 per c.mm. of blood. The latter figure probably more nearly
represents the true normal average, since the lower counts were
obtained for the most part by workers who used unreliable methods.
Physiologic variations are marked; thus, the number {166} increases as
one ascends to a higher altitude, and is higher in winter than in
summer. There are unexplained variations from day to day; hence a
single abnormal count should not be taken to indicate a pathologic
condition.
Pathologic variations are often very great. Owing to lack of knowledge
as to the origin of the platelets and to the earlier imperfect methods
of counting, the clinical significance of these variations is
uncertain. The following facts seem, however, to be established:
(_a_) In acute infectious diseases the number is subnormal or normal.
If the fever ends by crisis, the crisis is accompanied by a rapid and
striking increase.
(_b_) In secondary anemia plaques are generally increased, although
sometimes decreased. In pernicious anemia they are always greatly
diminished, and an increase should exclude the diagnosis of this
disease.
(_c_) They are decreased in chronic lymphatic leukemia, and greatly
increased in the myelogenous form.
(_d_) In purpura hæmorrhagica the number is enormously diminished.
Blood-plaques are difficult to count owing to the rapidity with which
they disintegrate and to their great tendency to adhere to any foreign
body and to each other. The method of Kemp, Calhoun, and Harris is
practical and is to be recommended:
* * * * *
Wash the finger well and allow a few minutes to elapse for the
circulation to become normal. Prick the finger lightly with a
blood-lancet, regulating the depth of the puncture so that the blood
will not flow without gentle pressure. Quickly dip a clean glass rod
into a vessel containing diluting and fixing fluid, and place two or
three good-sized drops upon the {167} finger over the puncture. Then
exert gentle pressure above the puncture so that a small drop of blood
will exude into the fluid. Mix the two by passing the rod lightly
several times over the surface of the blended drop. (Some workers
first place a drop of the fluid upon the finger and then make the
puncture through it, this necessitating less care as to depth of the
puncture.) Now transfer a drop of the diluted blood from the finger to
a watch-glass which contains two or three drops of the fluid, and mix
well. From this, transfer a drop to the counting slide of the
Thoma-Zeiss hemocytometer, and cover. An ordinary thin cover will
answer for this purpose, and is preferable because it allows the use
of a higher power objective. Allow the slide to stand for at least
five minutes, and then with a one-sixth or higher objective count the
plaques and the red corpuscles in a definite number of squares. At
least 100 plaques must be counted. The number of red corpuscles per
cubic millimeter of blood having been previously ascertained in the
usual manner (p. 152), the number of plaques can easily be calculated
by the following equation:
_r_:_p_ :: _R_:_P_; and _P_ = _p_ x _R_/_r_.
_r_ represents the number of red corpuscles in any given number of
squares; _p_, the number of plaques in the same squares; _R_, the
total number of red corpuscles per c.mm. of blood; and _P_, the number
of plaques per c.mm.
Beginners are apt to take too much blood and not to dilute it enough.
Best results are attained when there are only one or two plaques in a
small square. With insufficient dilution, the platelets are more or
less obscured by the red cells.
The following diluting and fixing fluid is recommended:
Formalin 10 c.c.
1 per cent. aqueous solution sodium chlorid 150 c.c.
(Color with methyl-violet if desired.)
{168} This fluid is cheap and easily prepared, and keeps indefinitely.
It fixes the plaques quickly without clumping, and does not clump nor
decolorize the reds. It has a low specific gravity, and hence allows
the plaques to settle upon the ruled area along with the reds. Fluids
of high specific gravity cause the plaques to float so that they do
not appear in the same plane with the reds and the ruled lines.
* * * * *
VI. STUDY OF STAINED BLOOD
A. MAKING AND STAINING BLOOD-FILMS
1. Spreading the Film.--Thin, even films are essential to accurate and
pleasant work. They more than compensate for the time spent in
learning to make them. There are certain requisites for success with
any method: (_a_) The slides and covers must be perfectly clean;
thorough washing with soap and water and rubbing with alcohol will
usually suffice; (_b_) the drop of blood must not be too large; (_c_)
the work must be done quickly, before coagulation begins.
The blood is obtained from the finger-tip or the lobe of the ear, as
for a blood count; only a very small drop is required.
* * * * *
Ehrlich's Two-cover-glass Method.--This method is very widely used,
but considerable practice is required to get good results. Touch a
cover-glass to the top of a small drop of blood, and place it, blood
side down, upon another cover-glass. If the drop be not too large, and
the covers be perfectly clean, the blood will spread out in a very
thin layer. Just as it stops spreading, before it begins to coagulate,
pull the covers quickly but firmly apart on a line parallel to their
plane (Fig. 74). It is best to handle the covers with forceps, since
the moisture of the fingers may produce artifacts.
Two-slide Method.--Place a small drop of blood upon a {169} clean
slide and push it along with the edge of a second slide held at an
angle of 45 degrees to the surface of the first (Fig. 75).
[Illustration: FIG. 74.--Spreading the film: two-cover-glass method.]
[Illustration: FIG. 75.--Spreading the film: two-slide method.]
Cigarette-paper Method.--This gives better results in the hands of the
inexperienced than any of the methods in general use, and may be used
with either slides or covers. A very thin paper, such as the "Zig-zag"
brand, is best. Ordinary cigarette paper and thin tissue-paper will
answer, but do not give nearly so good results.
Cut the paper into strips about ¾ inch wide, _across the ribs_. Pick
up one of the strips by the gummed edge, and touch its opposite end to
the drop of blood. Quickly place the end which has the blood against a
slide or a large cover-glass held {170} in a forceps. The blood will
spread along the edge of the paper. Now draw the paper evenly across
the slide or cover. A thin film of blood will be left behind (Fig.
76).
[Illustration: FIG. 76.--Spreading the film. Cigarette-paper method
applied to cover-glasses.]
* * * * *
The films may be allowed to dry in the air, or may be dried by gently
heating high above a flame (where one can comfortably hold the hand).
Such films will keep for years, but for some stains they must not be
more than a few weeks old. They must be kept away from flies--a fly
can work havoc with a film in a few minutes.
2. Fixing the Film.--In general, films must be "fixed" before they are
stained. Fixation may be accomplished by chemicals or by heat. Those
stains which are dissolved in methyl-alcohol combine fixation with the
staining process.
* * * * *
Chemic Fixation.--Soak the film five to fifteen minutes in pure
methyl-alcohol, or one-half hour or longer in equal parts of absolute
alcohol and ether. One minute in 1 per cent. formalin in alcohol is
preferred by some. Chemic fixation may precede eosin-methylene-blue
and other simple stains.
{171} Heat Fixation.--This may precede any of the methods which do not
combine fixation with the staining process; it _must_ be used with
Ehrlich's triple stain. The best method is to place the film in an
oven, raise the temperature to 150° C., and allow to cool slowly.
Without an oven, the proper degree of fixation is difficult to attain.
Kowarsky has devised a small plate of two layers of copper (Fig. 77),
upon which the films are placed together with a crystal of urea. The
plate is heated over a flame until the urea melts, and is then set
aside to cool. This is said to give the proper degree of fixation, but
in the writer's experience the films have always been underheated. He
obtains better results by use of tartaric acid crystals
(melting-point, 168°-170° C.). The plate, upon which have been placed
the cover-glasses, film side down, and a crystal of the acid, is
heated over a low flame until the crystal has completely melted. It
should be held sufficiently high above the flame that the heating will
require five to seven minutes. The covers are then removed. Freshly
made films of normal blood should be allowed to remain upon the plate
for a minute or two after heating has ceased. Fresh films require more
heat than old ones, and normal blood more than the blood of pernicious
anemia and leukemia.
[Illustration: FIG. 77.--Kowarsky's plate for fixing blood (Klopstock
and Kowarsky).]
Fixation by passing the film quickly through a flame about twenty
times, as is often done in routine work, is not recommended for
beginners.
* * * * *
3. Staining the Film.--The anilin dyes, which are extensively used in
blood work, are of two general classes: {172} basic dyes, of which
methylene-blue is the type; and acid dyes, of which eosin is the type.
Nuclei and certain other structures in the blood are stained by the
basic dyes, and are hence called _basophilic_. Certain structures take
up only acid dyes, and are called _acidophilic_, _oxyphilic_, or
_eosinophilic_. Certain other structures are stained only by
combinations of the two, and are called _neutrophilic_. Recognition of
these staining properties marked the beginning of modern hematology.
(1) Eosin and Methylene-blue.--In many instances this stain will give
all the information desired. It is especially useful in studying the
red corpuscles. Nuclei, basophilic granules, and all blood parasites
are blue; erythrocytes are red or pink; eosinophilic granules, bright
red. Neutrophilic granules and blood-plaques are not stained.
* * * * *
(1) Fix the film by heat or chemicals.
(2) Stain about five minutes with 0.5 per cent. alcoholic solution of
eosin, diluted one-half with water.
(3) Rinse in water, and dry between filter-papers.
(4) Stain one-half to one minute with saturated aqueous solution of
methylene-blue.
(5) Rinse well, dry, and mount. Films upon slides may be examined with
an oil-immersion objective without a cover-glass.
* * * * *
(2) Ehrlich's Triple Stain.--This has been the standard blood-stain
for many years, and is still widely used. It is probably the best for
neutrophilic granules. It is difficult to make, and should be
purchased ready prepared from a reliable dealer. Nuclei are stained
blue or greenish-blue; erythrocytes, orange; neutrophilic granules,
violet; and eosinophilic granules, copper red. {173} Basophilic
granules and blood-plaques are not stained (see Fig. 85).
Success in staining depends largely upon proper fixation. The film
must be carefully fixed by heat: underheating causes the erythrocytes
to stain red; overheating, pale yellow. The staining fluid is applied
for five to fifteen minutes, and the preparation is rinsed quickly in
water, dried, and mounted. Subsequent application of Löffler's
methylene-blue for one-half to one second will bring out the
basophilic granules, and improve the nuclear staining, but there is
considerable danger of overstaining.
(3) Wright's Stain.--Recently the polychrome methylene-blue-eosin
stains, dissolved in methyl-alcohol, have largely displaced other
blood-stains for clinical purposes. They combine the fixing with the
staining process, and stain differentially every normal and abnormal
structure in the blood. Numerous methods of preparing and applying
these stains have been devised. Wright's stain is one of the best, and
is the most widely used in this country. Directions for preparing it
are given in most of the newer large text-books upon clinical
diagnosis. The practitioner will find it best to purchase the stain
ready prepared. Most microscopic supply houses keep it in stock. The
method of application is as follows:
* * * * *
(1) Without previous fixation, cover the blood film with the stain,
and let stand one minute.
(2) Add water, drop by drop, until a delicate metallic scum forms upon
the surface. Let this mixture remain on the preparation for two or
three minutes.
(3) Wash in water until the better spread portions of the film have a
pinkish tint.
(4) Dry between filter-papers and mount.
* * * * *
{174} The stain is more conveniently applied upon cover-glasses than
upon slides. Films much more than a month old do not stain well. In
some localities ordinary tap-water will answer both for diluting the
stain and for washing the film; in others, distilled water must be
used. Different lots of Wright's fluid vary, and a few preliminary
stains should be made with each lot to learn its peculiarities. The
principal variation is in the amount of water which must be added to
obtain the iridescent scum. Sometimes eight or more drops must be
added after the scum appears.
When properly applied, Wright's stain gives the following picture
(Plate VI): erythrocytes, yellow or pink; nuclei, various shades of
bluish-purple; neutrophilic granules, reddish-lilac; eosinophilic
granules, bright red; basophilic granules of leukocytes and
degenerated red corpuscles, very dark bluish-purple; blood-plaques,
dark lilac; bacteria, blue. The cytoplasm of lymphocytes is generally
robin's-egg blue; that of the large mononuclears may have a faint
bluish tinge. Malarial parasites stain characteristically: the
cytoplasm, sky-blue; the chromatin, reddish-purple.
_Jenner's stain_, which gives a somewhat similar picture, is preferred
by many for differential counting of leukocytes. It brings out
neutrophilic granules rather more clearly, but does not compare with
Wright's fluid as a stain for the malarial parasite. Unfixed films are
stained about three minutes, rinsed quickly, dried, and mounted.
For the physician who wishes to use only one blood-stain, Wright's
fluid is undoubtedly the best of those mentioned.
[Illustration: PLATE VI. EXPLANATION OF PLATE VI.
Stained with Wright's stain. All drawn to same scale.
1, Normal red corpuscle for comparison; 2, normoblasts, one with
lobulated nucleus; 3, megaloblast and microblast. The megaloblast
shows a considerable degree of polychromatophilia; 4, blood-plaques,
one lying upon a red corpuscle; 5, lymphocytes, large and small; 6,
large mononuclear leukocyte; 7, transitional leukocyte; 8,
polymorphonuclear neutrophilic leukocytes; 9, eosinophilic leukocytes,
one ruptured; 10, basophilic leukocyte; 11, neutrophilic myelocyte.
The granules are sometimes less numerous and less distinct than here
shown; 12, eosinophilic myelocytes; 13, basophilic myelocyte; 14,
"irritation" or "stimulation" form, with small vacuoles; 15,
degenerated leukocytes: two polymorphonuclear neutrophiles, one
ruptured, one swollen and vacuolated; and a "basket cell" composed of
an irregular meshwork of nuclear material; 16, large mononuclear
leukocyte containing pigment-granules: from a case tertian malaria;
17, four stages in the asexual cycle of the tertian malarial parasite:
the second and fourth were drawn from the same slide taken from a case
of double tertian; 18, red corpuscle containing tertian parasite and
showing malarial stippling; 19, estivo-autumnal malarial parasites:
two small ring forms within the same red cell, and a crescent with
remains of the red corpuscle in its concavity.]
{175} B. STUDY OF STAINED FILMS
Much can be learned from stained blood-films. They furnish the best
means of studying the morphology of the blood and blood parasites,
and, to the experienced, they give a fair idea of the amount of
hemoglobin and the number of red and white corpuscles. A
one-twelfth-inch objective is required.
1. Erythrocytes.--Normally, the red corpuscles are acidophilic. The
colors which they take with different stains have been described. When
not crowded together, they appear as circular, homogeneous discs, of
nearly uniform size, averaging 7.5 µ in diameter (Fig. 84). The center
of each is somewhat paler than the periphery. The degree of pallor
furnishes a rough index to the amount of hemoglobin in the corpuscle.
They are apt to be crenated when the film has dried too slowly.
Pathologically, red corpuscles vary in size and shape, staining
properties, and structure.
(1) Variations in Size and Shape (See Plate VIII and Fig. 84).--The
cells may be abnormally small (called _microcytes_, 5 µ or less in
diameter); abnormally large (_macrocytes_, 10 to 12 µ); or extremely
large (_megalocytes_, 12 to 20 µ).
Variation in shape is often very marked. Oval, pyriform, caudate,
saddle-shaped, and club-shaped corpuscles are common. They are called
_poikilocytes_, and their presence is spoken of as poikilocytosis.
Red corpuscles which vary from the normal in size and shape are
present in most symptomatic anemias, and in the severer grades are
often very numerous. Irregularities are particularly conspicuous in
leukemia and pernicious anemia, where, in some instances, a normal
erythrocyte {176} is the exception. In pernicious anemia there is a
decided tendency to large size and oval forms, and megalocytes are
rarely found in any other condition.
(2) Variations in Staining Properties (See Plate VIII).--These include
polychromatophilia, basophilic degeneration, and basophilic stippling.
They are probably degenerative changes, although polychromatophilia is
thought by many to be evidence of youth in a cell, and hence to
indicate an attempt at blood regeneration.
(_a_) _Polychromatophilia_.--Some of the corpuscles partially lose
their normal affinity for acid stains, and take the basic stain to
greater or less degree. Wright's stain gives such cells a faint bluish
tinge when the condition is mild, and a rather deep blue when severe.
Sometimes only part of a cell is affected. A few polychromatophilic
corpuscles can be found in marked symptomatic anemias. They occur most
abundantly in malaria, leukemia, and pernicious anemia.
(_b_) _Basophilic Granular Degeneration_ (_Degeneration of
Grawitz_).--This is characterized by the presence, within the
corpuscle, of small basophilic granules. They stain deep blue with
Wright's stain; not at all, with Ehrlich's triple stain. The cell
containing them may stain normally in other respects, or it may
exhibit polychromatophilia.
Numerous cells showing this degeneration are commonly found in chronic
lead-poisoning, of which they were at one time thought to be
pathognomonic. Except in this disease, the degeneration indicates a
serious blood condition. It occurs in well-marked cases of pernicious
anemia and leukemia, and, much less commonly, in very severe
symptomatic anemias.
(_c_) _Basophilic Stippling_.--This term has been applied {177} to the
finely granular appearance often seen in red corpuscles, which harbor
malarial parasites (Plate VI). It is commonly classed with the
degeneration just described, but is probably distinct. Not all stains
will show it. With Wright's stain it can be brought out by staining
longer and washing less than for the ordinary blood-stain. The minute
granules stain reddish purple.
(3) Variations in Structure.--The most important is the presence of a
nucleus (Plates VI and VIII and Fig. 84). Nucleated red corpuscles, or
_erythroblasts_, are classed according to their size: _microblasts_,
5 µ or less in diameter; _normoblasts_, 5 to 10 µ; and _megaloblasts_,
above 10 µ. Microblasts and normoblasts contain one, rarely two,
small, round, sharply defined, deeply staining nuclei, often located
eccentrically. Occasionally the nucleus is irregular in shape,
"clover-leaf" forms being not infrequent. The megaloblast is probably
a distinct cell, not merely a larger size of the normoblast. Its
nucleus is large, stains rather palely, has a delicate chromatin
network, and often shows evidences of degeneration (karyorrhexis,
etc.). In ordinary work, however, it is safer to base the distinction
upon size than upon structure. Any nucleated red cell, but especially
the megaloblast, may exhibit polychromatophilia.
Normally, erythroblasts are present only in the blood of the fetus and
of very young infants. Pathologically, normoblasts occur in severe
symptomatic anemia, leukemia, and pernicious anemia. They are most
abundant in myelogenous leukemia. While always present in pernicious
anemia, they are often difficult to find. Megaloblasts are found in
pernicious anemia, and with extreme rarity in any other condition.
They almost invariably {178} exceed the normoblasts in number, which
is one of the distinctive features of the disease. Microblasts have
much the same significance as normoblasts, but are less common.
2. The Leukocytes.--An estimation of the number or percentage of each
variety of leukocyte in the blood is called a _differential count_.
The differential count is best made upon a film stained with Wright's,
Jenner's, or Ehrlich's stain. Go carefully over the film with an
oil-immersion lens, using a mechanical stage if available. Classify
each leukocyte seen, and calculate what percentage each variety is of
the whole number classified. For accuracy, 500 to 1000 leukocytes must
be classified; for approximate results, 200 are sufficient. Track of
the count may be kept by placing a mark for each leukocyte in its
appropriate column, ruled upon paper. Some workers divide a slide-box
into compartments with slides, one for each variety of leukocyte, and
drop a coffee-bean into the appropriate compartment when a cell is
classified. When a convenient number of coffee-beans is used (any
multiple of 100), the percentage calculation is extremely easy.
The actual number of each variety in a cubic millimeter of blood is
easily calculated from these percentages and the total leukocyte
count. An increase in actual number is an _absolute increase_; an
increase in percentage only, a _relative increase_. It is evident that
an absolute increase of any variety may be accompanied by a relative
decrease.
A record is generally kept of the number of nucleated red cells seen
during a differential count of leukocytes.
The usual classification of leukocytes is based upon their size, their
nuclei, and the staining properties of the granules {179} which many
of them contain. It is not altogether satisfactory, but is probably
the best which our present knowledge permits.
(1) Normal Varieties.--(_a_) Lymphocytes.--These are small mononuclear
cells without granules (Plate VI and Fig. 86). They are about the size
of a red corpuscle or slightly larger, and consist of a single,
sharply defined, deeply staining nucleus, surrounded by a narrow rim
of protoplasm. The nucleus is generally round, but is sometimes
indented at one side. Wright's stain gives the nucleus a deep purple
color and the cytoplasm a pale robin's-egg blue in typical cells.
Larger forms of lymphocytes are frequently found, especially in the
blood of children, and are difficult to distinguish from the large
mononuclear leukocytes.
Lymphocytes are formed in the lymphoid tissues, including that of the
bone-marrow. They constitute, normally, 20 to 30 per cent. of all
leukocytes, or about 1000 to 3000 per c.mm. of blood. They are more
abundant in the blood of children.
The percentage of lymphocytes is usually moderately increased in those
conditions which give leukopenia, especially typhoid fever, chlorosis,
pernicious anemia, and many debilitated conditions. A marked increase,
accompanied by an increase in the total leukocyte count, is seen in
pertussis and lymphatic leukemia. In the latter, the lymphocytes
sometimes exceed 98 per cent.
(_b_) Large Mononuclear Leukocytes (Plate VI).--These cells are two or
three times the diameter of the normal red corpuscle. Each contains a
single round or oval nucleus, often located eccentrically. The zone of
protoplasm surrounding the nucleus is relatively wide. With {180}
Wright's stain the nucleus is less deeply colored than that of the
lymphocyte, while the cytoplasm is very pale blue or colorless, and
sometimes contains a few reddish granules. The size of the cell, the
width of the zone of cytoplasm, and the depth of color of the nucleus
are the points to be considered in distinguishing between large
mononuclears and lymphocytes. When large forms of the lymphocyte are
present, the distinction is often difficult or impossible. It is then
advisable to count the two cells together as lymphocytes. Indeed, they
are regarded by some hematologists as identical.
Large mononuclear leukocytes probably originate in the bone-marrow or
spleen. They constitute 2 to 4 per cent. of the total number of
leukocytes: 100 to 400 per c.mm. of blood. An increase is unusual
except in malaria, where it is quite constantly observed, and where
many of the cells contain ingulfed pigment.
(_c_) Transitional Leukocytes (Plate VI).--These are essentially large
mononuclears with deeply indented or horseshoe-shaped nuclei. A few
fine neutrophilic granules are sometimes present in their cytoplasm.
They are probably formed from the large mononuclears, and occur in the
blood in about the same numbers. The two cells are usually counted
together.
(_d_) Polymorphonuclear Neutrophilic Leukocytes (Plate VI).--There is
usually no difficulty in recognizing these cells. Their average size
is somewhat less than that of the large mononuclears. The nucleus
stains rather deeply, and is extremely irregular, often assuming
shapes comparable to letters of the alphabet, E, Z, S, etc. (Fig. 86).
Frequently there appear to be several separate nuclei, hence the
widely used name, "polynuclear {181} leukocyte." Upon careful
inspection, however, delicate nuclear bands connecting the parts can
usually be seen. The cytoplasm is relatively abundant, and contains
great numbers of very fine neutrophilic granules. With Wright's stain
the nucleus is bluish-purple, and the granules, reddish-lilac.
Polymorphonuclear leukocytes are formed in the bone-marrow from
neutrophilic myelocytes. They constitute 60 to 75 per cent. of all the
leukocytes: 3000 to 7500 per c.mm. of blood. Increase in their number
practically always produces an increase in the total leukocyte count,
and has already been discussed under "phagocytic leukocytosis." The
leukocytes of pus, _pus-corpuscles_, belong almost wholly to this
variety.
A comparison of the percentage of polymorphonuclear cells with the
total leukocyte count yields more information than a consideration of
either alone. With moderate infection and good resisting powers the
leukocyte count and the percentage of polymorphonuclears are increased
proportionately. When the polymorphonuclear percentage is increased to
a notably greater extent than is the total number of leukocytes, no
matter how low the count, either very poor resistance or a very severe
infection may be inferred. In the absence of acute infectious disease
a polymorphonuclear percentage of 85 or over points very strongly to
gangrene or pus-formation. On the other hand, except in children,
where the percentage is normally low, pus is uncommon with less than
80 per cent. of polymorphonuclears.
Normally, the cytoplasm of leukocytes stains pale yellow with iodin.
Under certain pathologic conditions the cytoplasm of many of the
polymorphonuclears stains {182} diffusely brown, or contains granules
which stain reddish-brown with iodin. This is called _iodophilia_.
Extracellular iodin-staining granules, which are present normally, are
more numerous in iodophilia.
This iodin reaction occurs in all purulent conditions except abscesses
which are thoroughly walled off or purely tuberculous abscesses. It is
of some value in diagnosis between serous effusions and purulent
exudates, between catarrhal and suppurative processes in the appendix
and Fallopian tube, etc. Its importance, however, as a diagnostic sign
of suppuration has been much exaggerated, since it may occur in any
general toxemia, such as pneumonia, influenza, malignant disease, and
puerperal sepsis.
To demonstrate iodophilia, place the air-dried films in a stoppered
bottle containing a few crystals of iodin until they become yellow.
Mount in syrup of levulose and examine with a one-twelfth objective.
(_e_) Eosinophilic Leukocytes, or "Eosinophiles" (Plate VI).--The
structure of these cells is similar to that of the polymorphonuclear
neutrophiles, with the striking difference that, instead of fine
neutrophilic granules, their cytoplasm contains coarse granules having
a strong affinity for acid stains. They are easily recognized by the
size and color of the granules, which stain bright red with Wright's
stain.
Eosinophiles are formed in the bone-marrow from eosinophilic
myelocytes. Their normal number varies from 50 to 400 per c.mm. of
blood, or 1 to 4 per cent. of the leukocytes. An increase is called
_eosinophilia_, and is better determined by the actual number than by
the percentage.
Slight eosinophilia is physiologic during menstruation. {183} Marked
eosinophilia is always pathologic. It occurs in a variety of
conditions, the most important of which are: infection by animal
parasites; bronchial asthma; myelogenous leukemia; scarlet fever; and
many skin diseases.
Eosinophilia may be a symptom of _infection by any of the worms_. It
is fairly constant in trichinosis, uncinariasis, filariasis, and
echinococcus disease. In this country an unexplained marked
eosinophilia warrants examination of a portion of muscle for _Trichina
spiralis_ (p. 255).
_True bronchial asthma_ commonly gives a marked eosinophilia during
and following the paroxysms. This is helpful in excluding asthma of
other origin. Eosinophiles also appear in the sputum in large numbers.
In _myelogenous leukemia_ there is almost invariably an absolute
increase of eosinophiles, although, owing to the great increase of
other leukocytes, the percentage is usually diminished. Dwarf and
giant forms are often numerous.
_Scarlet fever_ is frequently accompanied by eosinophilia, which may
help to distinguish it from measles.
Eosinophilia has been observed in a large number of _skin diseases_,
notably pemphigus, prurigo, psoriasis, and urticaria. It probably
depends less upon the variety of the disease than upon its extent.
(_f_) Basophilic Leukocytes or "Mast-cells" (Plate VI).--In general,
these resemble polymorphonuclear neutrophiles except that the nucleus
is less irregular and that the granules are larger and have a strong
affinity for basic stains. They are easily recognized. With Wright's
stain the granules are deep purple, while the nucleus is pale blue and
is nearly or quite hidden by the granules, so that its form is
difficult to make out. These granules are not colored by Ehrlich's
stain.
{184} The nature of mast-cells is undetermined. They probably
originate in the bone-marrow. They are least numerous of the
leukocytes in normal blood, rarely exceeding 0.5 per cent., or 25 to
50 per c.mm. A notable increase is limited almost exclusively to
myelogenous leukemia, where they are sometimes very numerous.
(2) Abnormal Varieties.--(_a_) Myelocytes (Plate VI).--These are large
mononuclear cells whose cytoplasm is filled with granules. Typically,
the nucleus occupies about one-half of the cell, and is round or oval.
It is sometimes indented, with its convex side in contact with the
periphery of the cell. It stains rather feebly. The average diameter
of this cell (about 15.75 µ) is greater than that of any other
leukocyte, but there is much variation in size among individual cells.
Myelocytes are named according to the character of their
granules--neutrophilic, eosinophilic, and basophilic myelocytes. These
granules are identical with the corresponding granules in the
leukocytes just described. The occurrence of two kinds of granules in
the same cell is rare.
Myelocytes are the bone-marrow cells from which the corresponding
granular leukocytes are developed. Their presence in the blood in
considerable numbers is diagnostic of myelogenous leukemia. The
neutrophilic form is the less significant. A few of these may be
present in very marked leukocytosis or any severe blood condition, as
pernicious anemia. Eosinophilic myelocytes are found only in
myelogenous leukemia, where they are often very numerous. The
basophilic variety is less common, and is confined to long-standing
severe myelogenous leukemia.
(_b_) Atypical Forms.--Leukocytes which do not fit in {185} with the
above classification are not infrequently met, especially in
high-grade leukocytosis, pernicious anemia, and leukemia. The nature
of most of them is not clear, and their number is usually so small
that they may be disregarded in making a differential count. Among
them are: (_a_) Border-line forms between polymorphonuclear
neutrophiles and neutrophilic myelocytes; (_b_) small neutrophilic
cells with a single round, deeply staining nucleus: they probably
result from division of polymorphonuclear neutrophiles; (_c_)
"irritation forms"--large non-granular mononuclear cells, whose
cytoplasm stains fairly deep purple with Wright's stain, and intense
brown with Ehrlich's: they appear in the blood under the same
conditions as myelocytes; (_d_) degenerated forms: vacuolated
leukocytes, or merely palely or deeply staining homogeneous or
reticulated masses of chromatin (Plate VI).
3. Blood-plaques.--These are not colored by Ehrlich's stain, nor by
eosin and methylene-blue. With Wright's stain they appear as spheric
or ovoid, reddish to violet, granular bodies, 2 to 4 µ in diameter.
When well stained, a delicate hyaline peripheral zone can be
distinguished. In ordinary blood-smears they are usually clumped in
masses. A single platelet lying upon a red corpuscle may easily be
mistaken for a malarial parasite (Plate VI).
Blood-platelets are being much studied at present, but, aside from the
facts mentioned under their enumeration (p. 165), little of clinical
value has been learned. They have been variously regarded as very
young red corpuscles (the "hematoblasts" of Hayem), as disintegration
products of leukocytes, as remnants of extruded nuclei of
erythrocytes, and as independent nucleated bodies. The most probable
explanation of their origin seems to be that of {186} J. H. Wright,
who, from his recent studies, regards them as detached portions of the
cytoplasm of certain giant-cells of the bone-marrow and spleen.
VII. BLOOD PARASITES
A study of blood bacteriology is useful, but is hardly practicable for
the practitioner. Most bacteria can be detected only by culture
methods. The _spirillum of relapsing fever_ can be identified by the
method for the malarial parasite in fresh blood. The blood must be
taken during a paroxysm. The organism is an actively motile spiral
thread, about four times the diameter of a red corpuscle in length.
The movements which its active motion causes among the corpuscles
render it conspicuous. It can also be seen in stained preparations
(Fig. 78). The disease has rarely been seen in the United States.
[Illustration: FIG. 78.--Spirillum of relapsing fever (Karg and
Schmorl).]
Of the numerous animal parasites which have been {187} found in the
blood, three are especially interesting clinically: _Plasmodium
malariæ_, _Filaria sanguinis hominis_, and _Trypanosoma hominis_.
1. Plasmodium Malariæ.--This organism is one of a large group, the
_hemosporidia_ (p. 247), many of which live within and destroy the red
corpuscles of various animals. Three varieties are associated with
malarial fever in man--the tertian, quartan, and estivo-autumnal
malarial parasites.
(1) Life Histories.--There are two cycles of development: one, the
_asexual_, in the blood of man; and the other, the _sexual_, in the
intestinal tract of a particular variety of mosquito.
(_a_) _Asexual Cycle_.--The young organism enters the blood through
the bite of the mosquito. It makes its way into a red corpuscle, where
it appears as a small, pale "hyaline" body. This body exhibits ameboid
movement and increases in size. Soon, dark-brown granules derived from
the hemoglobin of the corpuscle make their appearance within it. When
it has reached its full size--filling and distending the corpuscle in
the case of the tertian parasite, smaller in the others--the
pigment-granules gather at the center or at one side; the organism
divides into a number of small hyaline bodies, the spores or
merozoites; and the red corpuscle bursts, setting spores and pigment
free in the blood-plasma. This is called segmentation. It coincides
with, and by liberation of toxins causes, the paroxysm of the disease.
A considerable number of the spores are destroyed by leukocytes or
other agencies; the remainder enter other corpuscles and repeat the
cycle. Many of the pigment-granules are taken up by leukocytes. In
estivo-autumnal fever segmentation occurs in the {188} internal organs
and the segmenting and larger pigmented forms are not seen in the
peripheral blood.
The asexual cycle of the tertian organism occupies forty-eight hours;
of the quartan, seventy-two hours; of the estivo-autumnal, an
indefinite time--usually twenty-four to forty-eight hours.
The parasites are thus present in the blood in great groups, all the
individuals of which reach maturity and segment at approximately the
same time. This explains the regular recurrence of the paroxysms at
intervals corresponding to the time occupied by the asexual cycle of
the parasite. Not infrequently there is multiple infection, one group
reaching maturity while the others are still young; but the presence
of two groups which segment upon the same day is extremely rare.
Fevers of longer intervals--six, eight, ten days--are probably due to
the ability of the body, sometimes of itself, sometimes by aid of
quinin, to resist the parasites so that a number sufficient to cause a
paroxysm do not accumulate in the blood until after several
repetitions of the asexual cycle. In estivo-autumnal fever the regular
grouping, while usually present at first, is soon lost, thus causing
"irregular malaria."
(_b_) _Sexual Cycle_.--Besides the ameboid individuals which pass
through the asexual cycle, there are present with them in the blood
many individuals with sexual properties. These are called _gametes_.
They do not undergo segmentation. Many of them are apparently
extracellular, but stained preparations usually show them to be
surrounded by the remains of a corpuscle. In tertian and quartan
malaria they cannot easily be distinguished from the asexual
individuals until a variable time after the blood leaves the body,
when the male gamete sends out {189} one or more flagella. In
estivo-autumnal malaria the gametes take distinctive ovoid and
crescentic forms, and are not difficult to recognize. They are very
resistent to quinin and often persist in the blood long after the
ameboid forms have been destroyed, but are probably incapable of
continuing the disease until they have passed through the cycle in the
mosquito.
When a malarious person is bitten by a mosquito, the gametes are taken
with the blood into its stomach. Here a flagellum from the male unites
with the female, which soon thereafter becomes encysted in the wall of
the intestine. After a time it ruptures, liberating many minute rods,
or sporozoites, which have formed within it. These migrate to the
salivary glands, and are carried into the blood of the person whom the
mosquito bites. Here they enter red corpuscles as young malarial
parasites, and the majority pass through the asexual cycle just
described.
[Illustration: FIG. 79.--Mosquitos--_Culex_ (1) and _anopheles_ (2)
(Bergey).]
[Illustration: FIG. 80.--Showing, on the left, _anopheles_ in resting
position, its dappled wing, and the position of its larvæ in water; on
the right, _culex_ in resting position, its plain wing, and the
position of its larvæ in water. The arrows indicate the directions
taken by the larvæ when the water is disturbed (Abbott).]
The sexual cycle can take place only within the body of one genus of
mosquito, _anopheles_. Absence of this mosquito from certain districts
explains the absence of {190} malaria. It is distinguished from our
common house-mosquito, _culex_, by the relative lengths of proboscis
and palpi (Fig. 79), which can be seen with a hand-lens, by its
attitude when resting, and by its dappled wing (Fig. 80). Anopheles is
strictly nocturnal in its habits; it usually flies low, and rarely
travels more than a few hundred yards from its breeding-place,
although it may be carried by winds. These facts explain certain
peculiarities in malarial infection; thus, infection occurs
practically only at night; it is most common near stagnant water,
especially upon the side toward which the prevailing winds blow; and
the {191} danger is greater when persons sleep upon or near the ground
than in upper stories of buildings. The insects frequently hibernate
in warmed houses, and may bite during the winter. A mosquito becomes
dangerous in eight to fourteen days after it bites a malarious person,
and remains so throughout its life.
(2) Detection.--Search for the malarial parasite may be made in either
fresh blood or stained films. If possible, the blood should be
obtained a few hours before the chill--never during it nor within a
few hours afterward, since at that time (in single infections) only
the very young, unpigmented forms are present, and these are the most
difficult to find and recognize. Sometimes many parasites are found in
a microscopic field; sometimes, especially in estivo-autumnal
infection, owing to accumulation in internal organs, careful search is
required to find any, despite very severe symptoms. Quinin causes them
rapidly to disappear from the peripheral blood, and few or none may be
found after its administration. In the absence of organisms, the
presence of pigment granules within leukocytes--polymorphonuclears and
large mononuclears--may be taken as presumptive evidence of malaria.
Pigmented leukocytes (Plate VI) are most numerous after a paroxysm.
(_a_) _In Fresh Unstained Blood_ (Plate VII).--Obtain a small drop of
blood from the finger or lobe of the ear. Touch the center of a
cover-glass to the top of the drop and quickly place it, blood side
down, upon a slide. If the slide and cover be perfectly clean and the
drop not too large, the blood will spread out so as to present only
one layer of corpuscles. Search with a one-twelfth-inch objective,
using very subdued light.
{192} The young organisms appear as small, round, ring-like or
irregular, colorless bodies within red corpuscles. The light spots
caused by crenation and other changes in the corpuscles are frequently
mistaken for them, but are generally more refractive or have more
sharply defined edges. The older forms are larger colorless bodies
containing granules of brown pigment. In the case of the tertian
parasite, these granules have active vibratory motion, which renders
them conspicuous; and as the parasite itself is very pale, one may see
only a large pale corpuscle in which fine pigment-granules are
dancing. Segmenting organisms, when typical, appear as rosets, often
compared to daisies, the petals of which represent the segments, while
the central brown portion represents the pigment. Tertian segmenting
forms are less frequently typical than quartan. Flagellated forms are
not seen until ten to twenty minutes after the blood has left the
vessels. As Cabot suggests, one should, while searching, keep a sharp
lookout for unusually large or pale corpuscles, and for anything which
is brown or black, or in motion.
[Illustration: PLATE VII. EXPLANATION OF PLATE VII.
Various forms of malarial parasites (Thayer and Hewetson).
1 to 10, inclusive, Tertian organisms; 11 to 17, inclusive, quartan
organisms; 18 to 27, inclusive, estivo-autumnal organisms; 1, young
hyaline form; 2, hyaline form with beginning pigmentation; 3,
pigmented form; 4, full-grown pigmented form; 5, 6, 7, 8, segmenting
forms; 9, extracellular pigmented form; 10, flagellate form; 11, young
hyaline form; 12, 13, pigmented forms; 14, fully developed pigmented
form; 15, 16, segmenting forms; 17, flagellate form; 18, 19, 20,
ring-like and cross-like hyaline forms; 21, 22, pigmented forms; 23,
24, segmenting forms; 25, 26, 27, crescents.]
(_b_) _In Stained Films_ (Plate VI).--Recognition of the parasite,
especially the young forms, is much easier in films stained by
Wright's or some similar stain than in fresh blood. When very scarce,
they may sometimes be found, although their structure is not well
shown, by the method of Ruge. This consists in spreading a very thick
layer of blood, drying, placing for a few minutes in a fluid
containing 5 per cent. formalin and 1 per cent. acetic acid, which
removes the hemoglobin and fixes the smear, rinsing, drying, and
finally staining. If Wright's stain be used in this method, it is
recommended that the {193} preparation be subsequently stained for a
half-minute with borax-methylene-blue (borax, 5; methylene-blue, 2;
water, 100).
In films which are properly stained with Wright's fluid the young
organisms are small, round, ring-like or irregular, sky-blue bodies,
each with a very small, sharply defined, reddish-purple chromatin
mass. Many structures--deposits of stain, dirt, blood-plaques lying
upon red cells, etc.--may simulate them, but should not deceive one
who looks carefully for both the blue cytoplasm and the reddish-purple
chromatin. A plaque upon a red corpuscle is surrounded by a colorless
zone rather than by a distinct blue body. Young estivo-autumnal
parasites commonly take a "ring" form (the chromatin mass representing
the jewel), which is infrequently assumed by the other varieties. The
older tertian and quartan organisms show larger sky-blue bodies with
more reticular chromatin, and contain brown granules of pigment,
which, however, is less evident than in the living parasite. The
chromatin is often scattered through the cytoplasm or apparently
outside of it, and is sometimes difficult to see clearly. Typical
"segmenters" present a ring of rounded segments or spores, each with a
small, dot-like chromatin mass. With the tertian parasite, the
segments more frequently form an irregular cluster. The pigment is
collected near the center or scattered among the segments. In
estivo-autumnal fever usually only the small "ring bodies" and the
crescentic and ovoid gametes are seen in the blood. The gametes are
easily recognized. Their length is somewhat greater than the diameter
of a red corpuscle. Their chromatin is usually centrally placed, and
they contain more or less coarse pigment. The remains of the {194} red
cell often form a narrow rim around them or fill the concavity of the
crescent.
While the parasites are more easily found in stained preparations, the
varieties are more easily differentiated in fresh blood. The chief
distinguishing points are included in the following table:
VARIETIES OF THE MALARIAL ORGANISM
TERTIAN. | QUARTAN. | ESTIVO-AUTUMNAL.
----------------------+----------------------+----------------------
Asexual cycle, | Seventy-two hours. | Usually twenty-four
forty-eight hours. | | to forty-eight hours.
----------------------+----------------------+----------------------
Substance pale, | Highly refractive, | Highly refractive.
transparent, | comparable to waxy |
comparable to hyaline | tube-cast. |
tube-cast. | |
----------------------+----------------------+----------------------
Outline indistinct. | Distinct. | Distinct.
----------------------+----------------------+----------------------
Ameboid motion | Sluggish. | Active.
active. | |
----------------------+----------------------+----------------------
Mature asexual form | Smaller. | Young forms, only, in
large; fills and | | peripheral blood.
often distends | |
corpuscle. | |
----------------------+----------------------+----------------------
Pigment-granules | Much coarser, darker | Very few, minute,
fine, brown, | in color, | inactive. Distinctly
scattered throughout. | peripherally | pigmented forms
Very active dancing | arranged. Motion | seldom seen.
motion. | slight. |
----------------------+----------------------+----------------------
Segmenting body | Usually typical | Not seen in
rarely assumes | "daisy." 6 to 12 | peripheral blood.
typical "daisy" form. | segments. |
15 to 20 segments. | |
----------------------+----------------------+----------------------
Gametes resemble | Same as tertian. | Appear in blood as
asexual forms. | | distinctive ovoids
| | and crescents.
----------------------+----------------------+----------------------
Red corpuscles pale | Generally darker | Dark, often bronzed.
and swollen. | than normal. |
----------------------+----------------------+----------------------
2. Filaria Sanguinis Hominis.--Of the several varieties of this worm,
_Filaria nocturna_ is most common and {195} most important clinically.
The adults are thread-like worms about 8 to 10 cm. long. They are
rarely seen. They live in pairs in the lymphatic channels and glands,
especially those of the pelvis and groin, and often occur in such
numbers as to obstruct the flow of lymph. This is the most common
cause of elephantiasis. Infection is very common in tropical
countries, especially in Samoa, the West Indies, Central America, and
the Isthmus of Panama. It is said that in Samoa 50 per cent. of the
natives are infected.
The female is viviparous, and produces vast numbers of embryos, which
appear in the circulating blood. These embryos are very actively
motile, worm-like structures, about as wide as a red corpuscle and 0.2
to 0.4 mm. long (Fig. 107). They are found in the peripheral blood
only at night, appearing about 8 P.M. and reaching their maximum
number--which is sometimes enormous--about midnight. If the patient
change his time of sleeping, they will appear during the day.
Infection is carried by a variety of mosquito, which acts as
intermediate host.
Diagnosis rests upon detection of embryos in the blood. They can be
seen in stained preparations, but are best found in fresh unstained
blood. A rather large drop is taken upon a slide, covered, and
examined with a low power. The embryo can be located by the commotion
which its active motion produces among the corpuscles. This motion
consists almost wholly in apparently purposeless lashing and coiling
movements, and continues for many hours.
3. Trypanosoma Hominis.--Various trypanosomes are common in the blood
of fishes, amphibians, birds, and {196} mammals (Fig. 81). They live
in the blood-plasma and do not attack the corpuscles. In some animals
they are apparently harmless; in others they are an important cause of
disease.
[Illustration: FIG. 81.--Trypanosomes from blood of gray rat
(Boston).]
_Trypanosoma hominis_ is an actively motile, spindle-shaped organism,
two or three times the diameter of a red corpuscle in length, with one
end terminating in a long flagellum. It can be seen with medium power
objectives in either fresh or stained blood. Human trypanosomiasis is
common in Africa. As a rule, it is a very chronic disease. "Sleeping
sickness" is a late stage when the organisms have invaded the
cerebrospinal fluid. Infection is carried by a biting fly, _Glossina
palpalis_.
VIII. SERUM REACTIONS
1. Agglutination.--In the blood-serum of persons suffering from
certain infectious diseases there exist soluble bodies, called
agglutinins, which have the property of {197} rendering non-motile and
clumping the specific micro-organism of the disease, and have little
or no influence upon other bacteria. This "agglutination" takes place
even when the blood is greatly diluted. Undiluted normal blood can
agglutinate most bacteria, but loses this power when diluted to any
considerable degree. These facts are taken advantage of in the
diagnosis of several diseases.
When applied to the diagnosis of typhoid fever, the phenomenon is
known as the _Widal reaction_. As yet, it is the only agglutination
reaction which has any practical value for the practitioner.
Either blood-serum or the whole blood may be used. Serum is the
better. To obtain it, it is convenient to use little vials, such as
can be made by breaking off the lower half-inch of the tubes which
have contained peptonizing powder. They must, of course, be well
cleaned. One of these is filled to a depth of about one-fourth inch
from a puncture in the finger, and is set aside for a few hours. When
the clot has separated, it is picked out with a needle, leaving the
serum. One drop of the serum is then added to nine drops of normal
salt solution, making a dilution of 1:10. Distilled water may be used
for dilution, but is more liable to cause error. The dilution can be
more accurately made in the leukocyte pipet of the Thoma-Zeiss
instrument. When the whole blood is used, it can be secured in the
pipet and at once diluted with the salt solution. When it must be
transported a considerable distance, dried blood is most convenient. A
large drop is allowed to dry upon a clean slide or unglazed paper. It
will keep for months without losing its agglutinating power. When
ready to make the test, the dried stain is dissolved in ten drops of
normal salt solution, care being {198} taken that the drops are about
the same size as the original drop of blood.
The reaction can be detected either microscopically or
macroscopically:
* * * * *
Microscopic Method.--(1) The blood or serum having been obtained and
diluted 1:10 as just described, mix it with a bouillon culture of the
typhoid bacillus to any desired dilution. One drop of each makes a
blood-dilution of 1:20, etc. The culture should be between eighteen
and twenty-four hours old, and the bacilli must be actively motile. A
stock agar culture should be kept at room temperature, and bouillon
tubes inoculated the day before the examination is to be made. Agar
cultures can be purchased from dealers in biologic products. They must
be renewed monthly.
Instead of the bouillon culture, McFarland recommends the use of a
suspension made by removing some of the growth from the surface of a
fresh agar culture and mixing it well with a little sterile water. It
is then necessary to examine the suspension microscopically to make
sure that there are no natural clumps.
(2) Place a few drops of the mixture of blood and culture upon a
perfectly clean slide and apply a cover-glass. The cover may be ringed
with vaselin to prevent evaporation, but this is not usually
necessary.
(3) Examine at intervals with a high dry lens--a one-sixth will answer
very well. The light must be very subdued. At first the bacilli should
be actively moving about. If the blood be from a case of typhoid, they
will gradually lose their motion and gather together in clumps (Fig.
82). The clumps should be large, and the few bacilli remaining
isolated should be motionless. Pseudo-reactions, in which there are a
few small clumps of bacilli whose motion is not entirely lost,
together with many freely moving bacilli scattered throughout the
field, should not mislead. As a control, a drop {199} of the culture
should always be examined before making the test.
[Illustration: FIG. 82.--Showing clumping of typhoid bacilli in the
Widal reaction. At one point a crenated red blood-corpuscle is seen
(Wright and Brown).]
Normal blood may produce clumping if time enough be allowed. The
diagnostic value of a positive reaction is, therefore, impaired unless
clumping takes place within a limited time. With dilution of 1:20 the
time limit should not exceed one-half hour; with 1:40, one hour. Tests
based upon lower dilution than 1:20 are probably not reliable.
Macroscopic Method.--The principle is the same as that of the
microscopic method. Clumping of the bacilli causes a flocculent
precipitate, which can be seen with the naked eye. A dead culture
gives the same results as a living one. This method is as reliable as
the microscopic and is more convenient for the practitioner, although
it requires more time.
Dead cultures, together with apparatus for diluting the blood, are put
up at slight cost by various firms under the names of typhoid
diagnosticum, typhoid agglutometer, etc. Full directions accompany
these outfits.
* * * * *
{200} The Widal reaction is positive in over 95 per cent. of all cases
of typhoid fever. It may, rarely, be positive in other conditions,
owing, sometimes at least, to faulty technic. It appears often as
early as the sixth or seventh day; usually during the second week. It
remains during the whole course of the disease, and frequently
persists for years.
2. Opsonins.--That phagocytosis plays an important part in the body's
resistance to bacterial invasion has long been recognized. According
to Metchnikoff, this property of leukocytes resides entirely within
themselves, depending upon their own vital activity. The recent
studies of Wright and Douglas, upon the contrary, indicate that the
leukocytes are impotent in themselves, and can ingest bacteria only in
the presence of certain substances which exist in the blood-plasma.
These substances have been named _opsonins_. Their nature is
undetermined. They probably act by uniting with the bacteria, thus
preparing them for ingestion by the leukocytes; but they do not cause
death of the bacteria, nor produce any appreciable morphologic change.
They appear to be more or less specific, a separate opsonin being
necessary for phagocytosis of each species of bacteria. There are,
moreover, opsonins for other formed elements--red blood-corpuscles,
for example. It has been shown that the quantity of opsonins in the
blood can be greatly increased by inoculation with dead bacteria.
To measure the amount of any particular opsonin in the blood Wright
has devised a method which involves many ingenious and delicate
technical procedures. Much skill, such as is attained only after
considerable training in laboratory technic, is requisite, and there
are many sources {201} of error. It is, therefore, beyond the province
of this work to recount the method in detail. In a general way it
consists in: (_a_) Preparing a mixture of equal parts of the patient's
blood-serum, an emulsion of the specific micro-organism, and a
suspension of washed leukocytes; (_b_) preparing a similar mixture,
using serum of a normal person; (_c_) incubating both mixtures for a
definite length of time; and (_d_) making smears from each, staining,
and examining with a one-twelfth objective. The number of bacteria
which have been taken up by a definite number of leukocytes is
counted, and the average number of bacteria per leukocyte is
calculated; this gives the "phagocytic index." The phagocytic index of
the blood under investigation, divided by that of the normal blood,
gives the _opsonic index_ of the former, the opsonic index of the
normal blood being taken as 1. Simon regards the percentage of
leukocytes which have ingested bacteria as a more accurate measurement
of the amount of opsonins than the number of bacteria ingested,
because the bacteria are apt to adhere and be taken in in clumps.
Wright and his followers regard the opsonic index as an index of the
power of the body to combat bacterial invasion. They claim very great
practical importance for it as an aid to diagnosis and as a guide to
treatment by the vaccine method. This method of treatment consists in
increasing the amount of protective substances in the blood by
injections of normal-salt suspensions of dead bacteria of the same
species as that which has caused and is maintaining the morbid
process, these bacterial suspensions being called "vaccines." The
opinion of the majority of conservative men seems to be that while
vaccine therapy is undoubtedly an important addition to our {202}
methods of treatment of bacterial infections, particularly of those
which are strictly local, yet the value of the opsonic index in
measuring resisting power or as an aid to diagnosis and guide to
treatment is still _sub judice_.
IX. TESTS FOR RECOGNITION OF BLOOD
1. Guaiac Test.--The technic of this test has been given (p. 89). It
may be applied directly to a suspected fluid, or, better, to the
ethereal extract. Add a few cubic centimeters of glacial acetic acid
to about 10 c.c. of the fluid; shake thoroughly with an equal volume
of ether; decant, and apply the test to the ether. In case of dried
stains upon cloth, wood, etc., dissolve the stain in distilled water
and test the water, or press a piece of moist blotting-paper against
the stain, and touch the paper with drops of the guaiac and the
turpentine successively.
[Illustration: FIG. 83.--Teichmann's hemin crystals (Jakob).]
2. Teichmann's Test.--This depends upon the production of
characteristic crystals of _hemin_. It is a sensitive test, and, when
positive, is absolute proof of the presence of blood. A number of
substances--lime, fine {203} sand, iron rust--interfere with
production of the crystals; hence negative results are not always
conclusive. Dissolve the suspected stain in a few drops of normal salt
solution upon a slide. If a liquid is to be tested, evaporate some of
it upon a slide and dissolve the residue in a few drops of the salt
solution. Let dry, apply a cover-glass, and run glacial acetic acid
underneath it. Heat _very gently_ until bubbles begin to form,
replacing the acid as it evaporates. Allow to cool slowly. When cool,
replace the acid with water, and examine for hemin crystals with
two-thirds and one-sixth objectives. The crystals are dark-brown
rhombic plates lying singly or in crosses, and are easily recognized
(Fig. 83). Failure to obtain them may be due to too great heat or too
rapid cooling. If not obtained at first, let the slide stand in a warm
place, as upon a hot-water radiator, for an hour.
X. SPECIAL BLOOD PATHOLOGY
The more conspicuous characteristics of the blood in various diseases
have been mentioned in previous sections. Although the great majority
of blood changes are secondary, there are a few blood conditions in
which the changes are so prominent, or the etiology so obscure, that
they are commonly regarded as blood diseases. These will receive brief
consideration here.
A. ANEMIA
This is a deficiency of hemoglobin, or red corpuscles, or both. It is
either primary or secondary. The distinction is based chiefly upon
etiology, although each type presents a more or less distinctive
blood-picture. Secondary anemia is that which is symptomatic of some
other {204} pathologic condition. Primary anemia is that which
progresses without apparent cause.
1. Secondary Anemia.--The more important conditions which produce
secondary or symptomatic anemia are:
(_a_) _Poor nutrition_, which usually accompanies unsanitary
conditions, poor and insufficient food, etc.
(_b_) _Acute infectious diseases_, especially rheumatism and typhoid
fever. The anemia is more conspicuous during convalescence.
(_c_) _Chronic infectious diseases_: tuberculosis, malaria, syphilis,
leprosy.
(_d_) _Chronic exhausting diseases_, as heart disease, chronic
nephritis, cirrhosis of the liver, and gastro-intestinal diseases,
especially when associated with atrophy of gastric and duodenal
glands. The last may give an extreme anemia, indistinguishable from
pernicious anemia.
(_e_) _Chronic poisoning_, as from lead, arsenic, and phosphorus.
(_f_) _Hemorrhage_--either repeated small hemorrhages, as from gastric
cancer and ulcer, uterine fibroids, etc., or a single large one.
(_g_) _Malignant tumors_: these affect the blood partly through
repeated small hemorrhages, partly through toxic products, and partly
through interference with nutrition.
(_h_) _Animal Parasites_.--Some cause no appreciable change in the
blood; others, like the _Uncinaria_ and _Bothriocephalus latus_, may
produce a very severe anemia, almost identical with pernicious anemia.
Anemia in these cases is probably due both to toxins and to
abstraction of blood.
The blood-picture varies with the grade of anemia. {205} Diminution of
hemoglobin is the most characteristic feature. In mild cases it is
slight, and is the only blood change to be noted. In very severe cases
hemoglobin may fall to 15 per cent. Red corpuscles are diminished in
all but very mild cases, while in the severest cases the red corpuscle
count is sometimes below 2,000,000. The color index is usually
decreased.
Although the number of leukocytes bears no relation to the anemia,
leukocytosis is common, being due to the same cause.
Stained films show no changes in very mild cases. In moderate cases
variations in size and shape of the red cells and polychromatophilia
occur. Very severe cases show the same changes to greater degree, with
addition of basophilic degeneration and the presence of normoblasts in
small or moderate numbers. Megaloblasts in very small numbers have
been encountered in extremely severe cases. Blood-plaques are usually
increased.
2. Primary Anemia.--The commonly described varieties of primary anemia
are pernicious anemia and chlorosis, but splenic anemia may also be
mentioned under this head.
(1) Progressive Pernicious Anemia.--It is frequently impossible to
diagnose this disease from the blood examination alone. Severe
secondary anemia sometimes gives an identical picture. Remissions, in
which the blood approaches the normal, are common. All the clinical
data must, therefore, be considered.
Hemoglobin and red corpuscles are always greatly diminished. In none
of Cabot's 139 cases did the count exceed 2,500,000, the average being
about 1,200,000. In more than two-thirds of the cases hemoglobin was
{206} reduced to less extent than the red corpuscles: the color-index
was, therefore, high. A low color-index probably indicates a mild type
of the disease.
The leukocyte count may be normal, but is commonly diminished to about
3000. The decrease affects chiefly the polymorphonuclear cells, so
that the lymphocytes are relatively increased. In some cases a decided
absolute increase of lymphocytes occurs. Polymorphonuclear
leukocytosis, when present, is due to some complication.
[Illustration: FIG. 84.--_A_, Normal blood; _B_, chlorosis; _C_,
pernicious anemia. The plate shows the sharp contrast between cells
rich in hemoglobin and the pale cell of chlorosis, and also the
poikilocytosis and marked variations in size noted in pernicious
anemia. A normoblast and megaloblast also appear. Stained smears (from
Greene's "Medical Diagnosis").]
[Illustration: PLATE VIII. EXPLANATION OF PLATE VIII.
Fig. 1.--Preparation from an advanced case of progressive pernicious
anemia from unknown cause: _a_, Megaloblasts or gigantoblasts; the
protoplasm shows marked polychromasia; _b_, stained granules in
erythrocytes with normally stained protoplasm; _c_ and _d_,
polychromatophilic degeneration; _e_, megalocytes; _f_, normocytes.
Fig. 2.--Preparation from the same case taken some time later while
the patient was subjectively and objectively in perfect health: _a_,
Punctate erythrocytes with normal and anemic degenerated protoplasm;
_b_, polynuclear leukocyte; _c_, normal red blood-corpuscles; _d_,
somewhat enlarged erythrocytes.
Fig. 3.--Series of cells from a case of severe progressive pernicious
anemia of unknown etiology; preparation made two days antemortem: _a_,
Nucleated red blood-corpuscles characterized as normoblasts by the
intense staining of the nuclei; _a'_ and _a"_, karyokinetic figures in
erythrocytes; the protoplasm finely punctate; _b_, beginning
karyolysis in a megaloblast; _c_, erythroblasts with coarse
granulation of the protoplasm; _d_, nuclear remains (?) and fine
granulation of the protoplasm; _e_ and _f_, finely punctate red
blood-corpuscles; _g_, megalocyte with two blue nuclei; nuclear
remains (?) in the polychrome protoplasm.
(Nothnagel-Lazarus.)]
The red corpuscles show marked variation in size and shape (Plate VIII
and Fig. 84). There is a decided {207} tendency to large oval forms,
and despite the abundance of microcytes, the average size of the
corpuscles is generally strikingly increased. Polychromatophilia and
basophilic degeneration are common. Nucleated red cells are always
present, although in many instances careful search is required to find
them. In the great majority of cases megaloblasts exceed normoblasts
in number. This ratio constitutes one of the most important points in
diagnosis, since it is practically unknown in other diseases.
Blood-plaques are diminished.
The rare and rapidly fatal anemia which has been described under the
name of _aplastic anemia_ is probably a variety of pernicious anemia.
Absence of any attempt at blood regeneration explains the marked
difference in the blood picture. Red corpuscles and hemoglobin are
rapidly diminished to an extreme degree. The color index is normal or
low. The leukocyte count is normal or low, with relative increase of
lymphocytes. Stained smears show only slight variations in size,
shape, and staining properties of the red cells. There are no
megaloblasts, and few or no normoblasts.
(2) Chlorosis.--The clinical symptoms furnish the most important data
for diagnosis. The blood resembles that of secondary anemia in many
respects.
The most conspicuous feature is a decided decrease of hemoglobin (down
to 30 or 40 per cent. in marked cases), accompanied by a slight
decrease in number of red corpuscles. The color-index is thus almost
invariably low, the average being about 0.5.
As in pernicious anemia, the leukocytes are normal or decreased in
number, with a relative increase of lymphocytes.
{208} In contrast to pernicious anemia (and in some degree also to
secondary anemia) the red cells are of nearly uniform size, are
uniformly pale (Fig. 84), and their average diameter is somewhat less
than normal. Changes in size, shape, and staining reactions occur only
in severe cases. Erythroblasts are rarely present. The number of
plaques is generally decreased.
(3) Splenic Anemia.--This is an obscure form of anemia associated with
great enlargement of the spleen. It is probably a distinct entity.
There is decided decrease of hemoglobin and red corpuscles, with
moderate leukopenia and relative lymphocytosis. Osler's fifteen cases
averaged 47 per cent. hemoglobin and 3,336,357 red cells. Stained
films show notable irregularities in size, shape, and staining
properties only in advanced cases. Erythroblasts are uncommon.
B. LEUKEMIA
Except in rare instances, diagnosis is easily made from the blood
alone. Two types of the disease are commonly distinguished: the
_myelogenous_ and the _lymphatic_. Atypical and intermediate forms are
not uncommon. Pseudoleukemia, because of its clinical similarity to
lymphatic leukemia, is generally described along with leukemia.
1. Myelogenous Leukemia.--This is usually a chronic disease, although
acute cases have been described.
Hemoglobin and red corpuscles show decided decrease. The color-index
is moderately low.
Most striking is the immense increase in number of leukocytes. The
count in ordinary cases varies between 100,000 and 300,000. Counts
over 1,000,000 have been {209} met. During remissions, the leukocyte
count may fall to normal.
While these enormous leukocyte counts are equaled in no other disease,
and approached only in lymphatic leukemia and extremely high-grade
leukocytosis, the diagnosis, particularly during remissions, depends
more upon qualitative than quantitative changes. Although all
varieties are increased, the characteristic and conspicuous cell is
the myelocyte. This cell never appears in normal blood; extremely
rarely in leukocytosis; and never abundantly in lymphatic leukemia. In
myelogenous leukemia myelocytes usually constitute more than 20 per
cent. of all leukocytes. Da Costa's lowest case gave 7 per cent. The
neutrophilic form is generally much more abundant than the
eosinophilic. Both show considerable variations in size. Very constant
also is a marked absolute, and often a relative, increase of
eosinophiles and basophiles. Polymorphonuclear neutrophiles and
lymphocytes are relatively decreased.
[Illustration: FIG. 85.--Blood from a case of splenomedullary
leukemia, stained with Ehrlich's triple stain (Jakob).]
{210} The red cells show the changes characteristic of a severe
secondary anemia, except that nucleated reds are commonly abundant; in
fact, no other disease gives so many. They are chiefly of the
normoblastic type. Megaloblasts are uncommon. Blood-plaques are
generally increased.
[Illustration: FIG. 86.--Blood: Lymphatic leukemia (lower section);
marked leukocytosis (upper section). Stained smears. Compare types of
leukocytes with Fig. 85 (from Greene's "Medical Diagnosis").]
2. Lymphatic Leukemia.--This form may be either acute or chronic.
There is marked loss of hemoglobin and red corpuscles. The color-index
is usually moderately low.
The leukocyte count is high, but lower than in the myelogenous type.
Counts of 100,000 are about the average, but in many cases are much
lower. This high {211} count is referable almost wholly to increase of
lymphocytes. They generally exceed 90 per cent. of the total number.
In chronic cases they are chiefly of the small variety; in acute
cases, of the large form. Myelocytes are rare.
The red corpuscles show the changes usual in severe secondary anemia.
Erythroblasts are seldom abundant. Blood-plaques are decreased.
3. Pseudoleukemia (Hodgkin's disease) resembles lymphatic leukemia in
that there is marked and progressive enlargement of the lymph-nodes.
There is, however, no distinctive blood-picture. The changes in
hemoglobin and red cells resemble those of a moderate symptomatic
anemia, with rather low color-index. The leukocytes are commonly
normal in number and relative proportions.
4. Anæmia Infantum Pseudoleukæmica.--Under this name von Jaksch
described a rare disease of infancy, the proper classification of
which is uncertain. There is enlargement of liver and spleen, and
sometimes of lymph-nodes, together with the following blood-changes:
grave anemia with deformed and degenerated red cells and many
erythroblasts of both normoblastic and megaloblastic types; great
increase in number of leukocytes (20,000 to 100,000), and great
variations in size, shape, and staining of leukocytes, with many
atypical forms and a few myelocytes.
The table on the following page contrasts the distinctive
blood-changes in the more common conditions.
{212} DIFFERENTIAL DIAGNOSIS OF BLOOD DISEASES
SECONDARY | PERNICIOUS | | MYELOGENOUS | LYMPHATIC
ANEMIA. | ANEMIA. | CHLOROSIS. | LEUKEMIA. | LEUKEMIA.
-------------+-------------+-------------+-------------+------------
Hemoglobin.
Diminished | Diminished. | Greatly | Decidedly | Markedly
according to | | diminished. | diminished. | diminished.
degree of | | | |
anemia. | | | |
-------------+-------------+-------------+-------------+------------
Red Corpuscle Count.
Normal in | Greatly | Slightly | Decidedly | Markedly
mild cases; | diminished. | diminished. | diminished. | diminished.
diminished | | | |
in all | | | |
others. | | | |
-------------+-------------+-------------+-------------+------------
Color-index.
Normal or | High. | Low. | Usually | Usually
slightly | | | slightly | slightly
diminished. | | | diminished. | diminished.
-------------+-------------+-------------+-------------+------------
Leukocyte Count.
Not | Normal or | Normal or | Extremely | Very high.
necessarily | diminished. | diminished. | high. |
affected; | | | |
leukocytosis | | | |
common. | | | |
-------------+-------------+-------------+-------------+------------
Red Corpuscles on Stained Films.
Variations | Marked | Nearly | Similar to | Similar to
in size and | variations | uniform size| secondary | secondary
shape in | in size, | and shape; | anemia, | anemia.
moderate | shape, and | average size| except | Erythro-
cases; | staining | decreased; | normoblasts | blasts not
variations | reactions. | pale | generally | numerous.
in staining | Average size| centers. | very |
reactions | increased. | Erythro- | numerous. |
and | Tendency to | blasts very | |
normoblasts | large oval | rare. | |
in severe | forms. | | |
cases. | Erythro- | | |
| blasts | | |
| always | | |
| present; | | |
| megaloblasts| | |
| exceed | | |
| normoblasts.| | |
-------------+-------------+-------------+-------------+------------
Leukocytes on Stained Films.
Normal | Lymphocytes | Lymphocytes | Large | Lymphocytes
proportions | relatively, | apt to be | numbers of | exceed 90
or increase | sometimes | relatively | myelocytes | per cent.
of | absolutely, | increased. | (average, 20| Other
polynuclears.| increased. | | per cent.). | varieties
| | | Absolute | relatively
| | | increase of | decreased.
| | | eosinophiles|
| | | and |
| | | basophiles. |
| | | Relative |
| | | decrease of |
| | | polynuclears|
| | | and |
| | | lymphocytes.|
-------------+-------------+-------------+-------------+------------
{213}