[1] The evidence for his authorship may be found in Gabriel Harvey's
_Pierce's Supererogation_ (written November 1589, published 1593), in
Nash's _Have with you to Saffron Walden_ (1596), and in various
allusions in Lyly's own plays. See Fairholt's _Dramatic Works of John
Lilly_, i. 20.
LYME REGIS, a market town and municipal borough and watering-place in
the western parliamentary division of Dorsetshire, England, 151 m.
W.S.W. of London by the London & South Western railway, the terminus of
a light railway from Axminster. Pop. (1901) 2095. It is situated at the
mouth of a narrow combe or valley opening upon a fine precipitous
coast-line; there is a sandy shore affording excellent bathing, and the
country inland is beautiful. The church of St Michael and All Angels is
mainly Perpendicular, but the tower (formerly central) and the portion
west of it are Norman. A guildhall and assembly rooms are the chief
public buildings. The principal industries are stone-quarrying and the
manufacture of cement. There is a curved pier of ancient foundation
known as the Cobb. The harbour, with a small coasting trade, is under
the authority of the corporation. The borough is under a mayor, 4
aldermen and 12 councillors. Area, 1237 acres.
No evidence of settlement on the site of Lyme Regis exists before that
afforded by a grant, dated 774, purporting to be by Cynewulf, king of
the West-Saxons, of land here to the church of Sherborne, and a similar
grant by King Aethelstan to the church of Glastonbury. In 1086 three
manors of Lyme are mentioned: that belonging to Sherborne abbey, which
was granted at the dissolution to Thomas Goodwin, who alienated it in
the following year; that belonging to Glastonbury, which seems to have
passed into lay lands during the middle ages, and that belonging to
William Belet. The last was acquired by the family of Bayeux, from whom
it passed by marriage to Elias de Rabayne, whose nephew, Peter Baudrat,
surrendered it to the crown in 1315-1316 when the king became lord of
one moiety of the borough, henceforth known as Lyme Regis. Lyme ranked
as a port in 1234, and Edward I. in 1284 granted to the town a charter
making it a free borough, with a merchant gild, and in the same year the
mayor and bailiffs are mentioned. In the following January the bailiffs
were given freedom from pleading without the borough, freedom from toll
and privileges implying considerable foreign trade; the importance of
the port is also evident from the demand of two ships for the king's
service in 1311. In 1332-1333 Edward III. granted Lyme to the burgesses
at a fee-farm of 32 marks; on the petition of the inhabitants, who were
impoverished by tempests and high tides, this was reduced to 100
shillings in 1410 and to 5 marks in 1481. In 1591 Elizabeth incorporated
Lyme, and further charters were obtained from James I., Charles II. and
William III. Lyme returned two members to parliament from 1295 to 1832
when the representation was reduced to one. The borough was
disfranchised in 1867. The fairs granted in 1553 for the 1st of February
and the 20th of September are now held on altered dates. Trade with
France in wine and cloth was carried on as early as 1284, but was
probably much increased on the erection of the Cobb, first mentioned in
1328 as built of timber and rock. Its medieval importance as the only
shelter between Portland Roads and the river Exe caused the burgesses to
receive grants of quayage for its maintenance in 1335 and many
subsequent years, while its convenience probably did much to bring upon
Lyme the unsuccessful siege by Prince Maurice in 1644. In 1685 Lyme was
the scene of the landing of James, duke of Monmouth, in his attempt upon
the throne.
LYMINGTON, a municipal borough and seaport in the New Forest
parliamentary division of Hampshire, England, 98 m. S.W. from London by
the London & South Western railway. Pop. (1901) 4165. It lies on the
estuary of the Lymington, which opens into the Solent. The church of St
Thomas à Becket is an irregular structure, dating from the reign of
Henry VI., but frequently restored. There is some coasting trade, and
yacht-building is carried on. Regular passenger steamers serve Yarmouth
in the Isle of Wight. In summer the town is frequented for sea-bathing.
It is governed by a mayor, 4 aldermen and 12 councillors. Area, 1515
acres.
There was a Roman camp near Lymington (_Lentune_, _Lementon_), and Roman
relics have been found, but there is no evidence that a town existed
here until after the Conquest. Lymington dates its importance from the
grant of the town to Richard de Redvers, earl of Devon, in the reign of
Henry I. No charter has been found, but a judgment given under a writ of
_quo warranto_ in 1578 confirms to the burgesses freedom from toll,
passage and pontage, the tolls and stallage of the quay and the right to
hold two fairs--privileges which they claimed under charters of Baldwin
de Redvers and Isabel de Fortibus, countess of Albemarle, in the 13th
century, and Edward Courtenay, earl of Devon, in 1405. The town was
governed by the mayor and burgesses until the corporation was reformed
in 1835. A writ for the election of a member to parliament was issued in
the reign of Edward III., but no return was made. From 1585 two members
were regularly returned; the number was reduced to one in 1867, and in
1885 the representation was merged in that of the county. Fairs on the
13th and 14th of May and the 2nd and 3rd of October, dating from the
13th century, are still held. The Saturday market probably dates from
the same century. Lymington was made a port in the reign of Henry I.,
and its large shipping trade led to frequent disputes with Southampton
as to the levying of duties. The case was tried in 1329 and decided
against Lymington, but in 1750 the judgment was reversed, and since then
the petty customs have been regularly paid. From an early date and for
many centuries salt was the staple manufacture of Lymington. The rise of
the mineral saltworks of Cheshire led to its decline in the 18th
century, and later the renewed importance of Southampton completed its
decay.
See E. King, _Borough and Parish of Lymington_ (London, 1879).
LYMPH and LYMPH FORMATION. Lying close to the blood-vessels of a limb or
organ a further set of vessels may be observed. They are very pale in
colour, often almost transparent and very thin-walled. Hence they are
frequently difficult to find and dissect. These are the lymphatic
vessels, and they are found to be returning a fluid from the tissues to
the bloodstream. When traced back to the tissues they are seen to divide
and ultimately to form minute anastomosing tubules, the _lymph
capillaries_. The capillaries finally terminate in the spaces between
the structures of the tissue, but whether their free ends are closed or
are in open communication with the tissue spaces is still undecided. The
study of their development shows that they grow into the tissue as a
closed system of minute tubes, which indicates that in all probability
they remain permanently closed. If we trace the lymphatic vessels
towards the thorax we find that in some part of their course they
terminate in structures known as lymphatic glands. From these again
fresh lymphatic vessels arise which carry the fluid towards the main
lymph-vessel, the _thoracic duct_. This runs up the posterior wall of
the thorax close to the aorta, and finally opens into the junction of
the internal jugular and left subclavian veins. The lymph-vessels from
the right side of the head and neck and from the right arm open,
however, into the right subclavian vein (see LYMPHATIC SYSTEM below).
_Chemical Constitution of Lymph._--The lymph collected from the thoracic
duct during hunger is almost water clear and yellowish in colour. Its
specific gravity varies from 1015 to 1025. It tastes salt and has a
faint odour. It is alkaline in reaction, but is much less alkaline than
blood-serum. Like blood it clots, but clots badly, only forming a soft
clot which quickly contracts. The lymph collected from a lymphatic
before it has passed through a lymph gland contains a few leucocytes,
and though the number of lymphocytes is greater in the lymph after it
has flowed through a gland it is never very great. In normal states
there are no red blood corpuscles.
The total solids amount to 3.6 to 5.7%, the variations depending upon
the amount of protein present. The lymph during hunger contains only a
minute quantity of fat. Sugar (dextrose) is present in the same
concentration as in the blood. The inorganic constituents are the same
as in blood, but apparently the amounts of Ca, Mg and P2O5 are rather
less than in serum. Urea is present to the same amount as in blood. If
the lymph be collected after a meal, one important alteration is to be
found. It now contains an abundance of fat in a very fine state of
subdivision, if fat be present in the food. The concentrations of
protein and dextrose are not altered during the absorption of these
substances.
_The Significance of Lymph._--In considering the significance and use of
lymph we must note in the first place that it forms an alternative
medium for the removal of water, dissolved materials, formed elements or
particles away from the tissues. All materials supplied to a tissue are
brought to it by the blood, and are discharged from the blood through
the capillary wall. They thus come to lie in the tissue spaces between
the cells, and from this supply of material in a dissolved state the
cells take up the food they require. In the opposite direction the cell
discharges its waste products into this same tissue fluid. The removal
of material from the tissue fluid may be effected either by its being
absorbed through the capillary wall into the bloodstream, or by sending
it into the lymphatic vessels and thus away from the tissue. From this
point of view the lymphatics may be looked upon in a sense as a drainage
system of the tissues. Again, besides discharging fluid and dissolved
material into the tissue spaces, the blood may also discharge
leucocytes, and under many conditions this emigration of leucocytes may
be very extensive. These also may leave the tissue space by the path of
the lymph channels. Moreover, the tissues are at any time liable to be
injured, and the injury as well as damaging many cells may cause rupture
of capillaries (as in bruising) with escape of red blood-cells into the
tissue spaces. If this occurs we know that the damaged cells are
destroyed and their débris removed either by digestion by leucocytes or
by disintegration and solution. The damage of a tissue also commonly
involves an infection of the damaged area with living micro-organisms,
and these are at once admitted to the tissue spaces. Hence we see that
the lymphatics may be provided as channels by which a variety of
substances can be removed from the tissue spaces. The question at once
arises, is the lymph channel at all times open to receive the materials
present in the tissue space? If such be the case, lymph is simply tissue
fluid, and anything that modifies the constitution or amount of the
tissue fluid should in like proportion lead to a variation in the amount
and constitution of the lymph. But if the lymph capillary is a closed
tubule at its commencement this does not follow.
From these considerations we see that in the first instance the whole
problem of lymph formation is intimately bound up with the study of the
interchanges of material between the blood and the various tissue cells.
The exchange of material between blood and tissue cell may possibly be
determined in one or both of two ways. Either it may result from changes
taking place within the tissue cell, or the tissue cell remaining
passive material may be sent to or withdrawn from it owing to a change
occurring either in the composition of the blood or to a change in the
circulation through the tissue. Let us take first the results following
increased activity of a tissue. We know that increased activity of a
tissue means increased chemical change within the tissue and the
production of new chemical bodies of small molecular size (e.g. water,
carbonic acid, &c.). The production of these metabolites means the
destruction of some of the tissue substance, and to make good this loss
the tissue must take a further amount of material from the blood. We
know that this takes place, and moreover that the waste products
resulting from activity are ultimately removed. The question then
becomes: When does this restoration take place, and what is the
intermediate state of the tissue? We know that increased activity is
always accompanied by an increase in the blood-supply, indicating a
greater supply of nutritive material, though it may be that, the
increased supply required at the actual time of activity is oxygen only.
Simultaneously the opportunity for a more rapid removal of the waste
products is provided. We have to inquire then: Does this increased
vascularity necessarily mean an increased outpouring of water and
dissolved material into the tissues, for this might follow directly
from the greater filling of the capillaries, or from the increased
attracting power of the tissues to water (osmotic effect) due to the
sudden production of substances of small molecular size within the
tissue? The other possibility is that the increased volume of blood sent
to the tissue is for the sole purpose of giving it a more rapid supply
of oxygen, and that the ordinary normal blood-supply would amply suffice
for renewing the chemical material used up during activity. Tissues
undoubtedly vary among themselves in the amount of water and other
materials they take from the blood when thrown into activity, and their
behaviour in this respect depends upon the work they are called upon to
perform. We must discriminate between the substance required by and
consumed by the tissue, the chemical food which on combustion yields the
energy by which the tissue performs work, and, on the other hand, the
substance taken from the blood and either with or without further
elaboration discharged from the tissue (as, for instance, in the process
of secretion). The tissue contains in itself a store of food amply
sufficient to enable it to continue working for a long time after its
blood-supply has been stopped, and everything indicates that the supply
of chemical energy to the tissue may be slow or even withheld for a
considerable time. Hence we are led to conclude that the increased flow
of blood sent to a tissue when it is thrown into activity is first and
foremost to give that tissue an increased oxygen supply; secondly, to
remove waste carbonic acid; thirdly, and only in the case of some
tissues, to provide water salts and other materials for the outpouring
of a secretion, as an instance of which we may take the kidney as a
type. Hence there is no need to suppose that an extensive accumulation
of fluid and dissolved substances takes place within a tissue when it
becomes active. This must be an accumulation which would lead to an
engorgement of the tissue spaces and then to a discharge of fluid along
the lymph channels. To enable us to determine the various points just
raised we must know whether an increased blood-supply to a tissue
necessarily means an increased exudation of fluid into the tissue
spaces, and moreover we must study the exchange of fluid between a
tissue and the blood under as varied a series of conditions as possible,
subsequently examining whether exchange of fluid and other substances
between the tissue and the blood necessarily determines quantitatively
the amount of lymph flowing from the tissue. Hence we will first study
the exchanges between the blood and a tissue, and then turn our
attention to the lymph-flow from the tissues.
_The Exchanges of Fluids and dissolved Substances between the Blood and
the Tissues._--Numerous experiments have been performed in studying the
conditions under which fluid passes into the tissues and tissue
spaces--or in the reverse direction into the blood. We may group them
into (1) conditions during which the total volume of circulating fluid
is increased or decreased; (2) conditions in which the character of the
blood is altered, e.g. it is made more watery or its saline
concentration is altered; (3) conditions in which the blood-supply to
the part is altered; (4) conditions in which the physical character of
the capillary wall is altered.
1. The total volume of blood in an animal has been increased among other
ways by the transfusion of the blood of one animal directly into the
veins of a second of the same species. It is found that within a very
short time a large percentage of the plasma has been discharged from the
blood-vessels. It has been sent into the tissues, notably the muscles,
and it may be noted in passing without producing any increase in the
lymph-flow from these vessels. An analogous experiment, but one which
avoids the fallacy introduced by injecting a second animal's blood, has
been performed by driving all the blood out of one hind limb by applying
a rubber bandage tightly round it from the foot upwards. This increases
the volume of blood circulating in the rest of the body, and again a
rapid disappearance of the fluid part of the blood from the vessels was
observed--the fluid being mainly sent into the muscles, as was indicated
by showing that the specific gravity of the muscles fell during the
experiment. The experiments converse to these have also been studied.
Bleeding is very rapidly followed by a large inflow of fluid into the
circulating blood--this fluid being derived from all the tissues, and
especially again from the muscles. Or again, when the bandage from the
limb in the above-cited experiment was removed, the total capacity of
the circulatory system was thereby suddenly increased, and it was found
that the total volume of blood increased correspondingly, the increased
volume of fluid being drawn from the tissues and especially again from
the muscles. The rapidity with which this movement of fluid into or out
of the blood takes place is very striking. The explanation usually
offered is that the movement is effected by changes in the capillary
pressure due to the alteration in the volume of blood circulating. While
this seems feasible when the volume of blood is increased, it does not
offer a satisfactory explanation of the rapid movement of fluid from the
tissues when the volume of the blood is decreased. One must therefore
look for yet further factors in this instance.
2. Let us next turn attention to the second of our three main
variations, viz. that in which the composition of the blood is altered.
It has long been known that the injection of water, or of solutions of
soluble bodies such as salts, urea, sugar, &c., leads to a very rapid
exchange of water and salts between the blood and the tissues. Thus if a
solution less concentrated than the blood be injected, the blood is
thereby diluted, but with very great rapidity water leaves the blood and
is taken up by the tissues. Again, if a strong sugar or salt solution be
injected, the first effect is a big discharge of water from the tissues
into the blood and the movement of fluid is effected with great
rapidity. In these instances a new physical factor is brought into play,
viz. that of osmosis. When a solution of lower osmotic pressure than the
blood is injected the osmotic pressure of the blood falls temporarily
below that of the tissues, and water is therefore attracted to the
tissues. The converse is the case when a solution of osmotic pressure
higher than the blood is injected. This at first sight seems to be an
all-sufficient explanation of the results recorded, but difficulties
arise when we find that the tissues are not equally active in producing
the effects. Thus it is found that the muscles and skin act as the chief
water dépôt, while such tissues as the liver, intestines or pancreas
take a relatively small share in the exchange. Again, when a strong
sodium chloride solution is injected a considerable part of the sodium
chloride is soon found to have left the blood, and it has been shown
that the chloride dépôt is not identical with the water dépôt. The lung,
for instance, is found to take up relatively far more of the salt than
other tissues. Simultaneously with the passage of the salt into the
tissue an exchange of water from the tissue into the blood can be
observed, both processes being carried out very rapidly. The result is
that the blood very quickly returns to a state in which its osmotic
pressure is only slightly raised; the tissue, on the other hand, loses
water and gains salt, and its osmotic pressure and specific gravity
therefore rises. Again, the tissues do not participate equally in
producing the final result, nor is the tissue which gives up the largest
amount of water necessarily that which gains the largest amount of salt.
The results following the injection of solutions of other bodies of
small molecular size, e.g. urea or sugar, are quite analogous to those
above described in the case of the non-toxic salt solutions. Hence we
see that the rate of exchange of fluid and dissolved substance between a
tissue and the blood can be extremely rapid and that the exchange can
take place in either direction. We may also conclude that the main cause
of the exchange, and possibly the only one, is the osmotic action set up
by the solution injected, and that muscle tissue is particularly active
in the process.
Seeing that a very considerable amount of water or of dissolved
substance can be taken up from the blood into a tissue, the question
next arises: Where is this material held, in the tissue cell or in the
tissue space? Immediately the water or salt leaves the blood it reaches
the tissue space, but unless the process be extreme in amount it
probably passes at once into the tissue cell itself and is stored there.
If the process is excessive oedema is set up and fluid accumulates in
the tissue space.
These, taken quite briefly, are some of the more important conditions
under which fluid exchanges, take place. They are selected here because
of the extent and rapidity of the changes effected.
3. The third factor which may bring about a change in the amount of
fluid sent to a tissue is a variation in the capillary pressure. A rise
in capillary pressure will, if filtration can occur through the
capillary wall, cause an increased exudation of fluid from the blood.
Thus the rise in general blood-pressure following the injection of a
salt solution could cause an increased filtration into the tissues. Or
again, the hydraemia following a salt injection would favour an
increased exudation because the blood would be more readily filtrable.
We, however, know very little of the effect of changes in capillary
pressure upon movement of fluid into the tissue spaces and tissues, most
of such observations being confined to a study of their effect upon
lymph-flow. We will therefore return to them in this connexion.
4. The remaining factor to be mentioned is a change in the character of
the capillary wall. It is well known that many poisons can excite an
increased exudation from the blood and the tissue may become oedematous.
Of such bodies we may mention cantharidin and the lymphogogues of Class
I (see later). A like change is also probably the cause of the oedema of
nephritis and of heart disease. It has also been suggested that the
capillaries of different organs show varying degrees of permeability, a
suggestion to which we will return later.
_Lymph Formation._--There are two theories current at the present day
offering explanations of the manner in which lymph is formed. The first,
which owes its inception to Ludwig, explains lymph formation upon
physical grounds. Thus according to this theory the lymphatics are open
capillary vessels at their origin in the tissues along which the tissue
fluid is driven. The tissue fluid is discharged from the blood by
filtration, and therefore its amount varies directly with the capillary
pressure. The amount of fluid movement also is further determined by
osmotic actions and by the permeability of the capillary wall.
The second theory first actively enunciated by Heidenhain regards lymph
formation as a secretory process of the capillary wall, i.e. one in the
discharge of which these cells perform work and are not merely passive
as in the former theory. As we shall see, it is now probable that
neither theory is completely correct.
In considering lymph formation we have to examine both the total amount
of lymph formed in the body and the variations in amount leaving each
separate organ under different conditions. In most investigations the
lymph was collected from the thoracic duct, i.e. it was the lymph
returned from all parts of the body with the exception of the right arm
and right side of the head and neck. The collection of the lymph from
organs is much more difficult to effect, and hence has not, to the
present, been so extensively studied. We will consider first variations
in the amount of the thoracic duct lymph. Lymph is always flowing along
the thoracic duct, and if the body is at rest, it has been shown that
this lymph is coming practically entirely from the intestines and liver,
chiefly, moreover, from the liver. The variations in the amount flowing
under various conditions has been extensively studied. We will discuss
them under the following headings: Changes brought about (a) by altered
circulatory conditions, (b) by the injection of various substances, and
(c) as a result of throwing an organ into activity.
Ligature of the portal vein leads to an increased flow of duct lymph.
Ligature of the inferior vena cava above the diaphragm also leads to a
large increase in the flow of duct lymph. Ligature of the aorta may
result in either an increased or decreased flow of direct lymph. One
explanation of these results has been offered from a study of the
changes in capillary pressure set up in the main organs involved. Thus,
after ligature of the portal vein the capillary pressure in the
intestines rises, and it was proved that the increase in thoracic duct
lymph came from the intestines. Ligaturing the inferior vena cava causes
a big rise in the pressure in the liver capillaries, the intestinal
capillary pressure remaining practically unaltered. Here it was proved
that the increase in lymph-flow came from the liver and was more
copious in amount than in the former instance. A further difference is
that this lymph is more concentrated, a feature which always
characterizes liver lymph. Ligature of the aorta may or may not cause a
rise in the liver capillary pressure, and it has been shown that if the
pressure rises there is an increased lymph-flow from the liver and
conversely. The increase of lymph comes entirely in this instance also
from the liver. It is in fact but a special instance of the former
experiment. From these results it has been argued that lymph formation
is simply a filtration fundamentally, and the lymph-flow is determined
mainly by the capillary pressure. Variations in the quantity of lymph
issuing from different organs have been on this theory ascribed to
differences in the permeability of the capillaries of the organs. Thus
as liver lymph is richest in protein content and is produced in greatest
amount, it has been concluded that the liver capillaries possess the
highest permeability. The intestines stand next in producing a
concentrated lymph, and their capillaries are therefore assumed to stand
second as regards permeability. Lastly, the lymph coming from limbs and
other organs is much poorer in solids and much less copious in amount.
Hence it is argued that their capillaries show the least permeability.
It is, however, very unsafe to compare the liver capillaries with those
of other organs, since they are not in reality capillaries but rather
venous sinuses, and their relation to the liver cells is
characteristically different from that of ordinary capillaries. If an
animal is at rest, no lymph flows from the hind limbs. To obtain a
sample of limb lymph it is necessary to massage the limb. If, however,
the veins to the limb be ligatured, we obtain a flow of lymph. The
ligature of course causes a rise of the capillary pressure, and it has
been argued that this rise of pressure starts a filtration through the
capillary wall and hence a flow of lymph. But the stoppage of the
blood-flow also damages the capillary wall and tissue cells by
asphyxiation, and the resulting lymph-flow is in all probability the
resultant of many complex processes. This case is analogous to the
production of oedema in cases of heart disease where the circulation is
feeble and the oxygen supply to the parts deficient. The results of
these experiments form the main evidence in support of the filtration
theory of lymph formation. They were first systematically studied by
Heidenhain, to whom we owe so much of our knowledge of lymph formation.
He did not, however, conclude that they established the filtration
theory.
In continuing his observations Heidenhain next studied the results
following the injection of a number of substances into the blood. He
found many which on injection gave rise to an increased lymph-flow from
the thoracic duct, and arranged them in two classes. As instances of
lymphogogues of the first class we may mention extract of mussels, leech
extract, peptone, extract of crayfish muscle, extract of strawberries,
of raspberries and many other like substances. Lymphogogues of the
second class comprise neutral salt solutions, urea, sugar, &c.
Considering the latter class first we may take as a type a solution of
sodium chloride. Injection of such a solution causes a large increase in
the lymph-flow, and it has been proved that the lymph comes from the
liver and intestines only--chiefly from the former. It is especially to
be noted that there is no lymph-flow from the limbs, and the same is
true for all lymphogogues of this class. As indicated above, the
injection of a saline solution leads to a large and rapidly effected
transport of fluid from the blood into muscle tissue, but though there
is this large increase in tissue fluid, no lymph flows from the tissue.
This result very powerfully disfavours the filtration theory of lymph
formation. It practically refutes the idea that lymph formation is
solely dependent upon such processes as filtration, osmosis and
capillary permeability only. It brings out quite clearly that the
exchange of fluid and dissolved salts, &c., between the blood and a
tissue, and the flow of lymph from that tissue, are two separate and
distinct processes, and especially that the first does not determine the
second. Also it is to be noted that the injection of a strong salt
solution also excites a flow of duct lymph, again arising from the liver
and intestines, but none from the limbs. In this instance, as previously
stated, the muscles of the limbs are losing water, and so presumably
are the liver and intestinal cells. This independence of tissue-blood
exchange and lymph-flow is distinctly in favour of the view, which is
rapidly gaining ground from histological observations, that in all
instances the lymphatics commence in a tissue as closed capillary
vessels.
Turning, in the next place, to the lymphogogues of the first class, it
has been proved that the origin of this increase of flow is again from
the liver. Very many of the substances of this class are bodies which
may when taken cause urticarial (nettle-rash) eruptions, a state which
is generally regarded as being due to an action upon the capillary
endothelium. Their action as lymphogogues is also generally ascribed to
an effect upon the capillary wall rendering it according to some more
permeable, according to others leading to a direct secretory action on
the part of the endothelium. We also know that many of the bodies of
this class act upon the liver in other directions than in exciting an
increased lymph production. Thus they may cause an increase in bile
secretion, or, as in the case of peptone, the liver cells may be excited
to produce a new chemical material, in this instance an antithrombin.
We have now to consider the effect of throwing an organ into activity
upon the lymph-flow from the organ. In all cases in which it has been
examined it is found that increased activity is accompanied by increased
lymph-flow. Thus, to take the instance of the submaxillary gland, which
at rest does not discharge any lymph, stimulation of the chorda tympani
is followed by a flow of lymph accompanying the flow of saliva
simultaneously excited. The stimulation of the nerve also produces
dilatation of the blood-vessels and therefore a rise in capillary
pressure. But that this vascular change is not the factor determining
the lymph-flow is proved by the administration of a small dose of
atropine, which arrests the secretion without influencing the vascular
reaction following chorda stimulation. After the atropine no lymph-flow
occurs on stimulating the nerve. Many other instances of a similar kind
might be adduced. Thus, we have seen that peptone specifically excites
the liver cells and also causes an increased lymph-flow from the liver;
or, as a last instance, the injection of bile salt excites a flow of
bile and also excites a flow of lymph from the liver. The supporters of
the filtration theory have argued that as activity of a tissue is
necessarily accompanied by the discharge of metabolites from the active
tissue cells, and as these are of small molecular size, they must set up
an osmotic effect. Water is therefore drawn into the tissue spaces, and
this rise in fluid content results mechanically in a flow of lymph from
the organ. The lymph simply drains away along the open lymphatics. This
argument, however, loses all its force when we recall the fact that we
may set up an enormous flow of fluid and salt into a tissue and its
tissue spaces without causing the least flow of lymph. Further, there is
no reason to suppose that the metabolites discharged from a tissue
during activity are produced in large quantities. The chief metabolite
is undoubtedly carbonic acid, and this diffuses very rapidly and is
quickly carried away by the blood. If, moreover, as is probably the
case, the lymphatics commence as closed capillaries, we have a further
difficulty in explaining how the fluid is driven through the lymphatic
wall. Either we must imagine the wall to be porous or there must be a
greater pressure outside than inside, and it is very difficult to
conceive how this is possible. As a general conclusion, then, it seems
much more probable that we are here dealing with a secretory process,
and that the active tissue produces some substance or substances--it may
be carbonic acid--which throws the lymphatic capillary cells into
activity.
To sum up in a few words the present state of our knowledge as to lymph
formation we may say that the exchange of water and salts between the
blood and the tissues is probably entirely determined by processes of
filtration and osmosis. Further, that the physical condition of the
capillary cells is frequently altered by many chemical substances, and
that in consequence it may permit exudation into the tissue spaces much
more freely. In the next place, the flow of lymph from a tissue is not
solely determined by the amount of the tissue fluids. The lymph
capillaries start as closed tubules, and the endothelial walls of these
tubules play an active part (secretory) in determining when water and
other substances shall be admitted into the capillary and further
determine the quantity of such discharge. Apparently, too, these cells
are specifically excited when the tissue is thrown into activity, the
exciting substance being a metabolite from the active tissue. Leucocytes
also are capable of passing through or between the endothelial cells of
the lymph capillary. (T. G. Br.)
LYMPHATIC SYSTEM. In anatomy, the lymphatic system (Lat. _lympha_, clear
water) comprises the _lymphoid_ or _adenoid_ tissue so plentifully
distributed about the body, especially in the course of the alimentary
canal (see CONNECTIVE TISSUES), _lymph spaces_, _lymphatic vessels_ of
which the lacteals are modifications, _lymphatic glands_, _haemolymph
glands_, and the _thoracic_ and _right lymphatic ducts_ by which the
lymph (q.v.) finally reaches the veins.
_Lymph spaces_ are mere spaces in the connective tissue, which usually
have no special lining, though sometimes there is a layer of endothelial
cells like those of the lymphatic and blood vessels. Most of these
spaces are very small, but sometimes, as in the case of the
_sub-epicranial space_ of the scalp, the _capsule of Tenon_ in the
orbit, and the _retropharyngeal space_ in the neck, they are large and
are adaptations to allow free movement. Opening from these spaces, and
also communicating with the serous membranes by small openings called
stomata,[1] are the _lymph capillaries_ (see VASCULAR SYSTEM), which
converge to the _lymphatic vessels_. These resemble veins in having an
internal layer of endothelium, a middle unstriped muscular coat, and an
external coat of fibrous tissue, though in the smaller vessels the
middle coat is wanting. They have numerous endothelial valves, formed of
two crescentic segments allowing the lymph to pass toward the root of
the neck. When the vessels are engorged these valves are marked by a
constriction, and so the lymphatics have a beaded appearance. The
vessels divide and anastomose very freely, and for this reason they do
not, like the veins, increase in calibre as they approach their
destination. It is usual to divide the lymphatic vessels into a
superficial and a deep set; speaking generally, the superficial ones are
found near the course of the superficial veins, while the deeper ones
accompany the arteries. Probably any single drop of lymph passes sooner
or later through one or more lymphatic glands, and so those vessels
which are approaching a gland are called _afferent_, while those leaving
are spoken of as _efferent lymphatics_. The _lacteals_ are special
lymphatic vessels which carry the chyle from the intestine; they begin
in lymphatic spaces in the villi and round the solitary and agminated
glands, and pass into the mesentery, where they come in contact with a
large number of _mesenteric glands_ before reaching the _receptaculum
chyli_.
The _lymphatic glands_ are pink bodies situated in the course of the
lymphatic vessels, to which they act as filters. They are generally oval
in shape and about the size of a bean, but sometimes, especially in the
groin, they form irregular flattened masses 2 in. long, while, at other
times, they are so small as almost to escape notice. They are usually
found in groups.
Each gland has a fibrous capsule from which trabeculae pass toward the
centre, where they break up and interlace, forming a network, and in
this way a cortical and medullary region for each gland is
distinguished; the intervals are nearly filled by lymphoid tissue, but
close to the trabeculae is a lymph path or sinus, which is only
crossed by the reticular stroma of the lymphoid tissue, and this
probably acts as a mechanical sieve, entangling foreign particles; as
an example of this the bronchial glands are black from carbon strained
off in its passage from the lungs, while the axillary glands in a
tattooed arm are blue. The blood-vessels enter at one spot, the
_hilum_, and are distributed along the trabeculae. In addition to
their function as filters the lymphatic glands are probably one of the
sources from which the leucocytes are derived.
The exact position of the various groups of glands is very important
from a medical point of view, but here it is only possible to give a
brief sketch which will be helped by reference to the accompanying
diagram. In the head are found _occipital_ and _mastoid glands_ (fig.
1, [beta]), which drain the back of the scalp; _internal maxillary_
_glands_, in the zygomatic fossa, draining the orbit, palate, nose
and membranes of the brain; _preauricular glands_ (fig. 1, [alpha]),
embedded in the parotid, draining the side of the scalp, pinna,
tympanum and lower eyelid; and _buccal glands_, draining the cheek
region. In the neck are the _superficial cervical glands_ (fig. 1,
[gamma]), along the course of the external jugular vein, draining the
surface of the neck; the _submaxillary glands_ (fig. 1, [delta]),
lying just above the salivary gland of the same name and draining the
front of the face and scalp; the _submental glands_ (fig. 1,
[epsilon]), beneath the chin, draining the lower lip, as well as
sometimes the upper, and the front of the tongue; the _retropharyngeal
glands_, draining the naso-pharynx and tympanum; the _pretracheal
glands_, draining the trachea and lower part of the thyroid body; and
the _deep cervical glands_, which are by far the most important and
form a great mass close to the internal jugular vein; they receive
afferent vessels from most of the glands already mentioned and so are
liable to be affected in any trouble of the head or neck, especially
of the deeper parts. Into them the lymphatics of the brain pass
directly. The lower part of this mass is sometimes distinguished as a
separate group called the _supra-clavicular glands_, which drain the
back of the neck and receive afferents from the occipital and axillary
glands. The efferents from the deep cervical glands join to form a
common vessel known as the _jugular lymphatic trunk_, and this usually
opens into the thoracic duct on the left side and the right lymphatic
duct on the right.
[Illustration: FIG. 1.--Superficial Lymphatic Vessels and Glands.
[alpha], Preauricular.
[beta], Mastoid.
[gamma], Superficial cervical.
[delta], Submaxillary.
[epsilon], Submental.
[zeta], Infraclavicular.
[eta], Anterior axillary.
[theta], Supratrochlear.
[iota], Antecubital.
[kappa], Inguinal.
[lambda], Superficial femoral.]
In the thorax are found _intercostal glands_ (fig. 2, I.), near the
vertebral column draining the back of the thoracic walls and pleura;
_internal mammary glands_, draining the front of the same parts as
well as the inner part of the breast and the upper part of the
abdominal wall; _diaphragmatic glands_, draining that structure and
the convex surface of the liver; _anterior, middle, posterior and
superior mediastinal glands_, draining the contents of those cavities.
The _bronchial glands_, draining the lungs, have already been referred
to.
In the abdomen and pelvis the glands are usually grouped round the
large arteries and are divided into visceral and parietal. Among the
visceral are the _gastric glands_, draining the stomach (these are
divided into _coronary_, _subpyloric_ and _retropyloric_ groups); the
_splenic glands_ at the hilum of the spleen, draining that organ, the
tail of the pancreas and the fundus of the stomach; the _hepatic
glands_ in the small omentum, draining the lower surface and deep
parts of the liver; the _pancreatic glands_, behind the lesser sac of
the peritoneum, draining the head and body of the pancreas, the
_superior mesenteric glands_; from one to two hundred in number, lying
in the mesentery and receiving the lacteals; the _ileo-caecal glands_,
draining the caecum, one of which is known as the _appendicular_ gland
and drains the vermiform appendix and right ovary; the _colic glands_
along the right and middle colic arteries, draining the ascending and
transverse colon; the _inferior mesenteric glands_ in the course of
that artery, draining the descending iliac and pelvic colons; the
_rectal_ glands, behind the rectum, draining its upper part.
Among the parietal glands are the _external iliac glands_, divided
into a lateral and mesial set (see fig. 2, E.I.), and receiving the
inguinal efferent vessels and lymphatics from the bladder, prostate,
cervix uteri, upper part of the vagina, glans penis vel clitoridis and
urethra. The _supra_ and _infra-umbilical glands_ receive the deep
lymphatics of the abdominal wall, the former communicating with the
liver, the latter with the bladder. From the latter, vessels pass to
the epigastric gland lying in front of the termination of the external
iliac artery. The _internal iliac glands_ (fig. 2, I. I.) are situated
close to the branches of this artery and drain the rectum, vagina,
prostate, urethra, buttock and perinaeum. _Common iliac glands_ (fig.
2, C.I.) lie around that artery and receive afferents from the
external and internal iliac glands as well as a few from the pelvic
viscera.[2] The _aortic glands_ are grouped all round the length of
the aorta, and are divided into _pre_-, _retro_- and _lateral aortic_
groups (fig. 2 P.A. and L), all of which communicate freely. The upper
preaortic glands are massed round the coeliac axis, and receive
afferents from the gastric, hepatic, splenic and pancreatic glands;
they are known as _coeliac glands_. The _lateral aortic glands_ drain
the kidney, adrenal, testis, ovary, fundus of uterus and lateral
abdominal walls. In the upper extremity a few small glands are
sometimes found near the deep arteries of the forearm. At the bend of
the elbow are the _ante-cubital_ glands (fig. 1 [lambda]) and just
above the internal condyle, one or two _supra-trochlear glands_ (fig.
1, [theta]). The _axillary glands_ (fig. 1, [eta]) are perhaps the
most practically important in the body. They are divided into four
sets: (1) _external_, along the axillary vessels, draining the greater
part of the arm; (2) _anterior_, behind the lower border of the
pectoralis major muscle, draining the surface of the thorax including
the breast and upper part of the abdomen; (3) _posterior_ along the
subscapular artery, draining the back and side of the trunk as low as
the umbilical zone; (4) superior or _infra-clavicular glands_ (fig. 1,
[zeta]), receiving the efferents of the former groups as well as
lymphatics accompanying the cephalic vein. In the lower limb all the
superficial lymphatics pass up to the groin, where there are two sets
of glands arranged like a T. The _superficial femoral_ glands (fig. 1,
[lambda]) are the vertical ones, and are grouped round the internal
saphenous vein; they are very large, drain the surface of the leg, and
are usually in two parallel rows. The _inguinal glands_ form the
cross bar of the T (fig. 1, [kappa]), and drain part of the buttock,
the surface of the abdomen below the umbilicus and the surface of the
genital organs. The deep lymphatics of the leg drain into the
_anterior tibial gland_ on that artery, the _popliteal glands_ in that
space, and the _deep femoral glands_ surrounding the common femoral
vein.
[Illustration: From A. M. Paterson, Cunningham's _Text-book of Anatomy_.
FIG. 2.--Deep Lymphatic Glands and Vessels of the Thorax and Abdomen
(diagrammatic). Afferent vessels are represented by continuous lines and
efferent and interglandular vessels by dotted lines.
C. Common iliac glands.
C.I. Common intestinal trunk.
D.C. Deep cervical glands.
E.I. External iliac glands.
I. Intercostal glands and vessels.
I.I. Internal iliac glands.
L. Lateral aortic glands.
M. Mediastinal glands and vessels.
P.A. Pre-aortic glands and vessels.
R.C. Receptaculum chylii.
R.L.D. Right lymphatic duct.
S. Sacral glands.
S.A. Scalenus anticus muscle.
T.D. Thoracic duct.]
The _thoracic duct_ begins as an irregular dilatation known as the
_receptaculum chyli_, opposite the first and second lumbar vertebrae,
which receives all the abdominal lymphatics as well as those of the
lower intercostal spaces. The duct runs up on the right of the aorta
through the posterior mediastinum and then traverses the superior
mediastinum to the left of the oesophagus. At the root of the neck it
receives the lymphatics of the left arm and left side of the neck and
opens into the beginning of the left innominate vein, usually by more
than one opening.
The _right lymphatic duct_ collects the lymphatics from the right side
of the neck and thorax, the right arm, right lung, right side of the
heart and upper surface of the liver; it is often represented by several
ducts which open separately into the right innominate vein.
_Haemolymph glands_ are structures which have only been noticed since
1884. They differ from lymphatic glands in their much greater
vascularity. They assist the spleen in the destruction of red blood
corpuscles, and probably explain or help to explain the fact that the
spleen can be removed without ill effects. In man they extend along the
vertebral column from the coeliac axis to the pelvis, but are specially
numerous close to the renal arteries.
T. Lewis suggests that lymphatic and haemolymph glands should be
classified in the following way:--
/ Haemal glands. / Simple.
| \ Specialized (Spleen)
|
Haemolymph | / 1. Blood and lymph sinuses
Glands. < Haemal lymphatic < separate.
| glands. | 2. Blood lymph sinuses.
| \ 3. Other combined forms.
|
\ Lymphatic glands.
Details and references will be found in papers by T. Lewis, _J. Anat.
& Phys._ vol. xxxviii. p. 312; W. B. Drummond, _Journ. Anat. and
Phys._ vol. xxxiv. p. 198; A. S. Warthin, _Journ. Med. Research_,
1901, p. 3, and H. Dayton, _Am. Journ. of Med. Sciences_, 1904, p.
448. For further details of man's lymphatic system see _The
Lymphatics_ by Delamere, Poirier and Cuneo, translated by C. H. Leaf
(London, 1903).
_Embryology._--The lymphatic vessels are possibly developed by the
hollowing out of mesenchyme cells in the same way that the arteries
are; these cells subsequently coalesce and form tubes (see VASCULAR
SYSTEM). There is, however, a good deal of evidence to show that they
are originally offshoots of the venous system, and that their
permanent openings into the veins are either their primary points of
communication or are secondarily acquired. The lymphatic and
haemolymph glands are probably formed by the proliferation of
lymphocytes around networks of lymphatic vessels; the dividing
lymphocytes form the lymphoid tissue, and eventually the network
breaks up to form distinct glands into which blood vessels penetrate.
If the blood vessels enlarge more than the lymphatic, haemolymph
glands result, but if the lymphatic vessels become predominant
ordinary lymphatic glands are formed. At an early stage in the embryo
pig two thoracic ducts are formed, one on either side of the aorta,
and the incomplete fusion of these may account for the division often
found in man's duct. In the embryo pig too there have been found two
pairs of lymph hearts for a short period.
See A. S. Warthin, _Journ. Med. Research_, vol. vii. p. 435; F. R.
Sabin, _Am. Journ. of Anat._ i., 1902; and, for literature,
_Development of the Human Body_, by J. P. McMurrich (London, 1906),
and Quain's _Anatomy_ (vol. i., London, 1908).
_Comparative Anatomy._--A lymphatic system is recognized in all the
Craniata, and in the lower forms (fishes and Amphibia) it consists
chiefly of lymph spaces and sinuses in communication with the coelom.
In fishes, for instance, there is a large _subvertebral lymph sinus_
surrounding the aorta and another within the spinal canal. In Amphibia
the subvertebral sinus is also found, and in the Anura (frogs and
toads) there is a great _subcutaneous lymph sinus_. _Lymph hearts_ are
muscular dilatations of vessels and are found in fishes, amphibians,
reptiles and bird embryos, and drive the lymph into the veins; they
are not known in adult mammals.
In birds the thoracic duct is first recognized, and opens into both
right and left precaval veins, as it always does in some mammals. In
birds, however, some of the lymphatics open into the sacral veins, and
it is doubtful whether true lymphatic glands ever occur. In birds and
mammals lymphatic vessels become more definite and numerous and are
provided with valves.
Haemolymph glands are present in mammals and birds, but have not been
seen lower in the scale, though S. Vincent and S. Harrison point out
the resemblance of the structure of the head kidney of certain
Teleostean fishes to them (_Journ. Anat. and Phys._ vol. xxxi. p.
176).
For further details see _Comparative Anat. of Vertebrates_, by R.
Wiedersheim (London, 1907). (F. G. P.)
_Diseases of the Lymphatic System and Ductless Glands._
_Lymphadenitis_ or inflammatory infection of the lymphatic glands, is
a condition characterized by hyperaemia of and exudation into the
gland, which becomes reader, firmer and larger than usual. Three
varieties may be distinguished: simple, suppurative and tuberculous.
The cause is always the absorption of some toxic or infective material
from the periphery. This may take place in several of the acute
infectious diseases, notably in scarlet fever, mumps, diphtheria and
German measles, or may be the result of poisoned wounds. The lymphatic
glands are also affected in constitutional diseases such as syphilis.
Simple lymphadenitis usually subsides of its own accord, but if toxins
are produced in the inflamed area the enlargement is obvious and
painful, while if pyogenic organisms are absorbed the inflammation
progresses to suppuration.
_Tuberculous lymphadenitis_ (scrofula) is due to the infection of the
lymph glands by Koch's tubercle bacillus. This was formerly known as
"King's Evil," as it was believed that the touch of the royal hand had
power to cure it. It occurs most commonly in children and young adults
whose surroundings are unhealthy, and who are liable to develop
tuberculous disease from want of sufficient food and fresh air. Some
local focus of irritation is usually present. The ways in which the
tubercle bacillus enters the body are much disputed, but catarrh of
the mucous membranes is regarded as a predisposing factor, and the
tonsils as a probable channel of infection. Any lymphoid tissue in the
body may be the seat of tuberculous disease, but the glands of the
neck are the most commonly involved. The course of the disease is slow
and may extend over a period of years. The earliest manifestation is
an enlargement of the gland. It is possible in this stage for
spontaneous healing to take place, but usually the disease progresses
to caseation, in which tuberculous nodules are found diffused
throughout the gland. Occasionally this stage may end in calcification
of the caseous matter, the gland shrinking and becoming hard; but
frequently suppuration follows from liquefaction of the caseating
material. Foci of pus occur throughout the gland, causing destruction
of the tissue, so that the gland may become a single abscess cavity.
If left to itself the abscess sooner or later bursts at one or several
points, leaving ulcerated openings through which a variable amount of
pus escapes. Temporary healing may take place, to be again followed by
further breaking down of the gland. This condition, if untreated, may
persist for years and may finally give rise to a general tuberculosis.
The treatment consists mainly in improving the general health with
good diet, fresh air (particularly sea air), cod-liver oil and iron,
and the removal of all sources of local irritation such as enlarged
tonsils, adenoids, &c. Vaccination with tuberculin (TR) may be useful.
Suppuration and extension of the disease require operative measures,
and removal of the glands _en masse_ can now be done through so small
an opening as to leave only a very slight scar.
In _Tabes mesenterica_ (tuberculosis of the mesenteric glands),
usually occurring in children, the glands of the mesentery and
retroperitonaeum become enlarged, and either caseate or occasionally
suppurate. The disease may be primary or may be secondary to
tuberculous disease of the intestines or to pulmonary phthisis. The
patients are pale, wasted and anaemic, and the abdomen may be
enormously enlarged. There is usually moderate fever, and thin watery
diarrhoea. The caseating glands may liquefy and give rise to an
inflammatory attack which may simulate appendicitis. Limited masses
are amenable to surgical treatment and may be removed, while in the
earlier stages constitutional treatment gives good results.
Tuberculous peritonitis frequently supervenes on this condition.
_Lymphadenoma_ (Hodgkin's Disease), a disease which was first fully
described by Hodgkin in 1832, is characterized by a progressive
enlargement of the lymphatic glands all over the body, and generally
starts in the glands of the neck. The majority of cases occur in young
adults, and preponderate in the male sex. The first symptom is usually
enlargement of a gland in the neck, with generally progressive growth
of the glands in the submaxillary region and axilla. The inguinal
glands are early involved, and after a time the internal lymph glands
follow. The enlargements are at first painless, but in the later
stages symptoms are caused by pressure on the surrounding organs, and
when the disease starts in the deeper structures the first symptoms
may be pain in the chest and cough, pain in the abdomen, pain and
oedema in the legs. The glands may increase until they are as large as
eggs, and later may become firmly adherent one to another, forming
large lobulated tumours. Increase of growth in this manner in the neck
may cause obstructive dyspnoea and even death. In the majority of
cases the spleen enlarges, and in rare instances lymphoid tumours may
be found on its surface. Anaemia is common and is secondary in
character; slight irregular fever is present, and soon a great and
progressive emaciation takes place. The cases are of two types, the
acute cases in which the enlargements take place rapidly and death may
occur in two to three months, and the chronic cases in which the
disease may remain apparently stationary. In acute lymphadenoma the
prognosis is very unfavourable. Recovery sometimes takes place in the
chronic type of the disease. Early surgical intervention has in some
cases been followed by success. The application of X-rays is a
valuable method of treatment, superficial glands undergoing a rapid
diminution in size. Of drugs arsenic is of the most service, and
mercurial inunction has been recommended by Dreschfeld. Organic
extracts have of late been used in the treatment of lymphadenoma.
_Glandular Fever_ is an acute infectious fever, generally occurring in
epidemics, and was first described by E. Pfeiffer in 1889. It usually
affects children and has a tendency to run through all the children of
a family. The incubation period is said to be about 7 days. The onset
is sudden, with pain in the neck and limbs, headache, vomiting,
difficulty in swallowing and high temperature. On the second day, or
sometimes on the first, swelling of the cervical glands is noticed,
and later the posterior cervical, axillary and inguinal glands become
enlarged and tender. In about half the cases the spleen and liver are
enlarged and there is abdominal tenderness. West found the mesenteric
nodes enlarged in 37 cases. Nephritis is an occasional complication,
and constipation is very usual. The disease tends to subside of
itself, and the fever usually disappears after a few days; the
glandular swellings may, however, persist from one to three weeks.
Considerable anaemia has been noticed to follow the illness. Rest in
bed while the glands are enlarged, and cod-liver oil and iron to meet
the anaemia, are the usual treatment.
_Status lymphaticus_ (lymphatism) is a condition found in children and
some adults, characterized by an enlargement of the lymphoid tissues
throughout the body and more particularly by enlargement of the thymus
gland. There is a special lowering of the patient's powers of
resistance, and it has been said to account for a number of cases of
sudden death. In all cases of status lymphaticus the thymus has been
found enlarged. At birth the gland (according to Bovaird and Nicoll)
weighs about 6 grammes, and does not increase after birth. In
lymphatism it may weigh from 10 to 50 grammes. The clinical features
are indefinite, and the condition frequently passes unrecognized
during life. In most cases there is no hint of danger until the fatal
syncope sets in, which may be after any slight exertion or shock, the
patient becoming suddenly faint, gasping and cyanosed, and the heart
stopping altogether before the respirations have ceased. The most
trifling causes have brought on fatal issues, such as a wet pack
(Escherich) or a hypodermic injection, or even a sudden plunge into
water though the head is not immersed. The greater number of deaths
occur during the administration of anaesthetics, which seem peculiarly
dangerous to these subjects. When an attack of syncope takes place no
treatment is of any avail.
Virchow, West and Goodhardt have described a form of asthma in adults
which they ascribe to a hypertrophied thymus gland and term "thymic
asthma."
_Diseases of the Spleen._--Physiological variations and abnormalities
and absence of the spleen are so rare as to require no comment. The
most usual pathological condition which gives rise to symptoms is that
of _wandering spleen_, which may or may not be secondary to a
wandering left kidney. It may produce symptoms of dragging and
discomfort, dyspepsia, vomiting and abdominal pain, and sometimes
jaundice (Treves), or the pedicle may become twisted, producing
extremely severe symptoms. The treatment is entirely surgical. Abscess
in the spleen occasionally occurs, usually in association with
infective endocarditis or with general pyaemia. The spleen may be the
seat of primary _new growths_, but these are rare, and only in a small
portion of cases does it share in the metastatic reproduction of
carcinoma. Infection of the spleen plays a prominent part in many
diseases, such as malaria, typhoid fever, lymphadenoma and leucaemia.
Diseases of the thyroid gland (see GOITRE) and _Addison's disease_ (of
the suprarenal glands) are treated separately. (H. L. H.)