RELATION OF DISEASE-BACTERIA TO MILK.
Practical experience with epidemic disease has abundantly demonstrated
the fact that milk not infrequently serves as a vehicle for the
dissemination of contagion. Attention has been prominently called to
this relation by Ernest Hart,[78] who in 1880 compiled statistical
evidence showing the numerous outbreaks of various contagious diseases
that had been associated with milk infection up to that time. Since
then, further compilations have been made by Freeman,[79] and also by
Busey and Kober,[80] who have collected the data with reference to
outbreaks from 1880 to 1899.
These statistics indicate the relative importance of milk as a factor in
the dissemination of disease.
The danger from this source is much intensified for the reason that
milk, generally speaking, is consumed in a raw state; and also because a
considerable number of disease-producing bacteria are able, not merely
to exist, but actually thrive and grow in milk, even though the normal
milk bacteria are also present. Moreover the recognition of the presence
of such pathogenic forms is complicated by the fact that often they do
not alter the appearance of the milk sufficiently so that their
presence can be detected by a physical examination. These facts which
have been experimentally determined, coupled with the numerous clinical
cases on record, make a strong case against milk serving as an agent in
the dissemination of disease.
~Origin of pathogenic bacteria in milk.~ Disease-producing bacteria may be
grouped with reference to their relation toward milk into two classes,
depending upon the manner in which infection occurs:
Class I. Disease-producing bacteria capable of being transmitted
directly from a diseased animal to man through the medium of infected
milk.
Class II. Bacteria pathogenic for man but not for cattle which are
capable of thriving in milk after it is drawn from the animal.
In the first group the disease produced by the specific organism must be
common to both cattle and man. The organism must live a parasitic life
in the animal, developing in the udder, and so infect the milk supply.
It may, of course, happen that diseases toward which domestic animals
alone are susceptible may be spread from one animal to another in this
way without affecting human beings.
In the second group, the bacterial species lives a saprophytic
existence, growing in milk, if it happens to find its way therein. In
such cases milk indirectly serves as an agent in the dissemination of
disease, by giving conditions favorable to the growth of the disease
germ.
By far the most important of diseases that may be transmitted directly
from animal to man through a diseased milk supply is tuberculosis, but
in addition to this, foot and mouth disease (aphthous fever in
children), anthrax and acute enteric troubles have also been traced to a
similar source of infection.
The most important specific diseases that have been disseminated through
subsequent pollution of the milk are typhoid fever, diphtheria, scarlet
fever and cholera, but, of course, the possibility exists that any
disease germ capable of living and thriving in milk may be spread in
this way. In addition to these diseases that are caused by the
introduction of specific organisms (the causal organism of scarlet fever
has not yet been definitely determined), there are a large number of
more or less illy-defined troubles of an intestinal character that occur
especially in infants and young children that are undoubtedly
attributable to the activity of microorganisms that gain access to milk
during and subsequent to the milking, and which produce changes in milk
before or after its ingestion that result in the formation of toxic
products.
DISEASES TRANSMISSIBLE FROM ANIMAL TO MAN THROUGH DISEASED MILK.
~Tuberculosis.~ In view of the wide-spread distribution of this disease in
both the human and the bovine race, the relation of the same to milk
supplies is a question of great importance. It is now generally admitted
that the different types of tubercular disease found in different kinds
of animals and man are attributable to the development of the same
organism, _Bacillus tuberculosis_, although there are varieties of this
organism found in different species of animals that are sufficiently
distinct to permit of recognition.
The question of prime importance is, whether the bovine type is
transmissible to the human or not. Artificial inoculation of cattle with
tuberculous human sputum as well as pure cultures of this variety show
that the human type is able to make but slight headway in cattle. This
would indicate that the danger of cattle acquiring the infection from
man would in all probability be very slight, but these experiments offer
no answer as to the possibility of transmission from the bovine to the
human. Manifestly it is impossible to solve this problem by direct
experiment upon man except by artificial inoculation, but comparative
experiments upon animals throw some light on the question.
Theo. Smith[81] and others[82] have made parallel experiments with
animals such as guinea pigs, rabbits and pigeons, inoculated with both
bovine and human cultures of this organism. The results obtained in the
case of all animals tested show that the virulence of the two types was
much different, but that the bovine cultures were much more severe.
While of course this does not prove that transmission from bovine to
human is possible, still the importance of the fact must not be
overlooked.
In a number of cases record of accidental infection from cattle to man
has been noted.[83] These have occurred with persons engaged in making
post-mortem examinations on tuberculous animals, and the tubercular
nature of the wound was proven in some cases by excision and
inoculation.
In addition to data of this sort that is practically experimental in
character, there are also strong clinical reasons for considering that
infection of human beings may occur through the medium of milk.
Naturally such infection should produce intestinal tuberculosis, and it
is noteworthy that this phase of the disease is quite common in
children especially between the ages of two and five.[84] It is
difficult to determine, though, whether primary infection occurred
through the intestine, for, usually, other organs also become involved.
In a considerable number of cases in which tubercular infection by the
most common channel, inhalation, seems to be excluded, the evidence is
strong that the disease was contracted through the medium of the milk,
but it is always very difficult to exclude the possibility of pulmonary
infection.
Tuberculosis as a bovine disease has increased rapidly during recent
decades throughout many portions of the world. This has been most marked
in dairy regions. Its extremely insidious nature does not permit of an
early recognition by physical means, and it was not until the
introduction of the tuberculin test[85] in 1892, as a diagnostic aid
that accurate knowledge of its distribution was possible. The quite
general introduction of this test in many regions has revealed an
alarmingly large percentage of animals as affected. In Denmark in 1894
over forty per cent were diagnosed as tubercular. In some parts of
Germany almost as bad a condition has been revealed. Slaughter-house
statistics also show that the disease has increased rapidly since 1890.
In this country the disease on the average is much less than in Europe
and is also very irregularly distributed. In herds where it gained a
foothold some years ago, often the majority of animals are frequently
infected; many herds, in fact the great majority, are wholly free from
all taint. The disease has undoubtedly been most frequently introduced
through the purchase of apparently healthy but incipiently affected
animals. Consequently in the older dairy regions where stock has been
improved the most by breeding, more of the disease exists than among the
western and southern cattle.
[Illustration FIG. 21: Front view of a tuberculous udder, showing extent
of swelling in single quarter.]
~Infectiousness of milk of reacting animals.~ Where the disease appears in
the udder the milk almost invariably contains the tubercle organism.
Under such conditions the appearance of the milk is not materially
altered at first, but as the disease progresses the percentage of fat
generally diminishes, and at times in the more advanced stages where the
physical condition of the udder is changed (Fig. 21), the milk may
become "watery"; but the percentage of animals showing such udder
lesions is not large, usually not more than a few per cent. (4 per cent.
according to Ostertag.)
On the other hand, in the earlier phases of the disease, where its
presence has been recognized solely by the aid of the tuberculin test,
before there are any recognizable physical symptoms in any part of the
animal, the milk is generally unaffected. Between these extremes,
however, is found a large proportion of cases, concerning which so
definite data are not available. The results of investigators on this
point are conflicting and further information is much desired. Some have
asserted so long as the udder itself shows no lesions that no tubercle
bacilli would be present,[86] but the findings of a considerable number
of investigators[87] indicate that even when the udder is apparently not
diseased the milk may contain the specific organism as revealed by
inoculation experiments upon animals. In some cases, however, it has
been demonstrated by post-mortem examination that discoverable udder
lesions existed that were not recognizable before autopsy was made. In
the experimental evidence collected, a varying percentage of reacting
animals were found that gave positive results; and this number was
generally sufficient to indicate that the danger of using milk from
reacting animals was considerable, even though apparently no disease
could be found in the udder.
The infectiousness of milk can also be proven by the frequent
contraction of the disease in other animals, such as calves and pigs
which may be fed on the skim milk. The very rapid increase of the
disease among the swine of Germany and Denmark,[88] and the frequently
reported cases of intestinal infection of young stock also attest the
presence of the organism in milk.
The tubercle bacillus is so markedly parasitic in its habits, that,
under ordinary conditions, it is incapable of growing at normal air
temperatures. There is, therefore, no danger of the germ developing in
milk after it is drawn from the animal, unless the same is kept at
practically blood heat.
Even though the milk of some reacting animals may not contain the
dangerous organism at the time of making the test, it is quite
impossible to foretell how long it will remain free. As the disease
becomes more generalized, or if tuberculous lesions should develop in
the udder, the milk may pass from a healthy to an infectious state.
This fact makes it advisable to exclude from milk supplies intended for
human use, all milk of animals that respond to the tuberculin test; or
at least to treat it in a manner so as to render it safe. Whether it is
necessary to do this or not if the milk is made into butter or cheese is
a somewhat different question. Exclusion or treatment is rendered more
imperative in milk supplies, because the danger is greater with children
with whom milk is often a prominent constituent of their diet, and also
for the reason that the child is more susceptible to intestinal
infection than the adult.
The danger of infection is much lessened in butter or cheese, because
the processes of manufacture tend to diminish the number of organisms
originally present in the milk, and inasmuch as no growth can ordinarily
take place in these products the danger is minimized. Moreover, the fact
that these foods are consumed by the individual in smaller amounts than
is generally the case where milk is used, and also to a greater extent
by adults, lessens still further the danger of infection.
Notwithstanding this, numerous observers[89] especially in Germany have
succeeded in finding the tubercle bacillus in market butter, but this
fact is not so surprising when it is remembered that a very large
fraction of their cattle show the presence of the disease as indicated
by the tuberculin test, a condition that does not obtain in any large
section in this country.
The observations on the presence of the tubercle bacillus in butter have
been questioned somewhat of late[2] by the determination of the fact
that butter may contain an organism that possesses the property of being
stained in the same way as the tubercle organism. Differentiation
between the two forms is rendered more difficult by the fact that this
tubercle-like organism is also capable of producing in animals lesions
that stimulate those of tuberculosis, although a careful examination
reveals definite differences. Petri[90] has recently determined that
both the true tubercle and the acid-resisting butter organism may be
readily found in market butter.
In the various milk products it has been experimentally determined that
the true tubercle bacillus is able to retain its vitality in butter for
a number of months and in cheese for nearly a year.
~Treatment of milk from tuberculosis cows.~ While it has been shown that
it is practically impossible to foretell whether the milk of any
reacting animal actually contains tubercle bacilli or not, still the
interests of public health demand that no milk from such stock be used
for human food until it has been rendered safe by some satisfactory
treatment.
_1. Heating._ By far the best treatment that can be given such milk is
to heat it. The temperature at which this should be done depends upon
the thermal death point of the tubercle bacillus, a question concerning
which there has been considerable difference of opinion until very
recently. According to the work of some of the earlier investigators,
the tubercle bacillus in its vegetative stage is endowed with powers of
resistance greater than those possessed by any other pathogenic
organism. This work has not been substantiated by the most recent
investigations on this subject. In determining the thermal death point
of this organism, as of any other, not only must the temperature be
considered, but the period of exposure as well, and where that exposure
is made in milk, another factor must be considered, viz., the presence
of conditions permitting of the formation of a "scalded layer," for as
Smith[91] first pointed out, the resistance of the tubercle organism
toward heat is greatly increased under these conditions. If tuberculous
milk is heated in a closed receptacle where this scalded membrane cannot
be produced, the tubercle bacillus is killed at 140 deg. F. in 15 to 20
minutes. These results which were first determined by Smith, under
laboratory conditions, and confirmed by Russell and Hastings,[92] where
tuberculous milk was heated in commercial pasteurizers, have also been
verified by Hesse.[93] A great practical advantage which accrues from
the treatment of milk at 140 deg. F. is that the natural creaming is
practically unaffected. Of course, where a higher temperature is
employed, the period of exposure may be materially lessened. If milk is
momentarily heated to 176 deg. F., it is certainly sufficient to destroy
the tubercle bacillus. This is the plan practiced in Denmark where all
skim milk and whey must be heated to this temperature before it can be
taken back to the farm, a plan which is designed to prevent the
dissemination of tuberculosis and foot and mouth disease by means of the
mixed creamery by-products. This course renders it possible to utilize
with perfect safety, for milk supplies, the milk of herds reacting to the
tuberculin test, and as butter of the best quality can be made from
cream or milk heated to even high temperatures,[94] it thus becomes
possible to prevent with slight expense what would otherwise entail a
large loss.
_2. Dilution._ Another method that has been suggested for the treatment
of this suspected milk is dilution with a relatively large volume of
perfectly healthy milk. It is a well known fact that to produce
infection, it requires the simultaneous introduction of a number of
organisms, and in the case of tuberculosis, especially that produced by
ingestion, this number is thought to be considerable. Gebhardt[95] found
that the milk of tuberculous cows, which was virulent when injected by
itself into animals, was innocuous when diluted with 40 to 100 times its
volume of healthy milk. This fact is hardly to be relied upon in
practice, unless the proportion of reacting to healthy cows is
positively known.
It has also been claimed in the centrifugal separation of cream from
milk[96] that by far the larger number of tubercle bacilli were thrown
out with the separator slime. Moore[97] has shown that the tubercle
bacilli in an artificially infected milk might be reduced in this way,
so as to be no longer microscopically demonstrable, yet the purification
was not complete enough to prevent the infection of animals inoculated
with the milk.
Another way to exclude all possibility of tubercular infection in milk
supplies is to reject all milk from reacting animals. This method is
often followed where pasteurization or sterilization is not desired. In
dairies where the keeping quality is dependent upon the exclusion of
bacteria by stringent conditions as to milking and handling ("sanitary"
or "hygienic" milk), the tuberculin test is frequently used as a basis
to insure healthy milk.
~Foot and mouth disease.~ The wide-spread extension of this disease
throughout Europe in recent years has given abundant opportunity to show
that while it is distinctively an animal malady, it is also
transmissible to man, although the disease is rarely fatal. The causal
organism has not been determined with certainty, but it has been shown
that the milk of affected animals possesses infectious properties[98]
although appearing unchanged in earlier phases of the disease.
Hertwig showed the direct transmissibility of the disease to man by
experiments made on himself and others. By ingesting milk from an
affected animal, he was able to produce the symptoms of the disease, the
mucous membrane of the mouth being covered with the small vesicles that
characterize the malady. It has also been shown that the virus of the
disease may be conveyed in butter.[99] This disease is practically
unknown in this country, although widely spread in Europe.
There are a number of other bovine diseases such as anthrax,[100]
lockjaw,[101] and hydrophobia[102] in which it has been shown that the
virus of the disease is at times to be found in the milk supply, but
often the milk becomes visibly affected, so that the danger of using the
same is greatly minimized.
There are also a number of inflammatory udder troubles known as garget
or mammitis. In most of these, the physical appearance of the milk is so
changed, and often pus is present to such a degree as to give a very
disagreeable appearance to the milk. Pus-forming bacteria (staphylococci
and streptococci) are to be found associated with such troubles. A
number of cases of gastric and intestinal catarrh have been reported as
caused by such milks.[103]
DISEASES TRANSMISSIBLE TO MAN THROUGH INFECTION OF MILK AFTER
WITHDRAWAL.
Milk is so well adapted to the development of bacteria in general, that
it is not surprising to find it a suitable medium for the growth of many
pathogenic species even at ordinary temperatures. Not infrequently,
disease-producing bacteria are able to grow in raw milk in competition
with the normal milk bacteria, so that even a slight contamination may
suffice to produce infection.
The diseases that are most frequently disseminated in this way are
typhoid fever, diphtheria, scarlet fever and cholera, together with the
various illy-defined intestinal troubles of a toxic character that occur
in children, especially under the name of cholera infantum, summer
complaint, etc.
Diseases of this class are not derived directly from animals because
cattle are not susceptible to the same.
~Modes of infection.~ In a variety of ways, however, the milk may be
subject to contaminating influences after it is drawn from the animal,
and so give opportunity for the development of disease-producing
bacteria. The more important methods of infection are as follows:
_1. Infection directly from a pre-existing case of disease on premises._
Quite frequently a person in the early stage of a diseased condition may
continue at his usual vocation as helper in the barn or dairy, and so
give opportunity for direct infection to occur. In the so-called cases
of "walking typhoid," this danger is emphasized. It is noteworthy in
typhoid fever that the bacilli frequently persist in the urine and in
diphtheria they often remain in the throat until after convalescence. In
some cases infection has been traced to storage of the milk in rooms in
the house where it became polluted directly by the emanations of the
patient.[104] Among the dwellings of the lower classes where a single
room has to be used in common this source of infection has been most
frequently observed.
_2. Infection through the medium of another person._ Not infrequently
another individual may serve in the capacity of nurse or attendant to a
sick person, and also assist in the handling of the milk, either in
milking the animals or caring for the milk after it has been drawn.
Busey and Kober report twenty-one outbreaks of typhoid fever in which
dairy employees also acted in the capacity of nurses.
_3. Pollution of milk utensils._ The most frequent method of infection
of cans, pails, etc., is in cleaning them with water that may be
polluted with disease organisms. Often wells may be contaminated with
diseased matter of intestinal origin, as in typhoid fever, and the use
of water at normal temperatures, or even in a lukewarm condition, give
conditions permitting of infection. Intentional adulteration of milk
with water inadvertently taken from polluted sources has caused quite a
number of typhoid outbreaks.[105] Sedgwick and Chapin[106] found in the
Springfield, Mass., epidemic of typhoid that the milk cans were placed
in a well to cool the milk, and it was subsequently shown that the well
was polluted with typhoid fecal matter.
_4. Pollution of udder_ of animal _by wading in infected water_, or by
washing same with contaminated water. This method of infection would
only be likely to occur in case of typhoid. An outbreak at the
University of Virginia in 1893[107] was ascribed to the latter cause.
_5. Pollution of creamery by-products, skim-milk, etc._ Where the milk
supply of one patron becomes infected with pathogenic bacteria, it is
possible that disease may be disseminated through the medium of the
creamery, the infective agent remaining in the skim milk after
separation and so polluting the mixed supply. This condition is more
likely to prevail with typhoid because of the greater tolerance of this
organism for acids such as would be found in raw milk. The outbreaks at
Brandon,[108] England, in 1893, Castle Island,[109] Ireland, and
Marlboro,[110] Mass., in 1894, were traced to such an origin.
While most outbreaks of disease associated with a polluted milk supply
originate in the use of the milk itself, yet infected milk may serve to
cause disease even when used in other ways. Several outbreaks of typhoid
fever have been traced to the use of ice cream where there were strong
reasons for believing that the milk used in the manufacture of the
product was polluted.[111] Hankin[112] details a case of an Indian
confection made largely from milk that caused a typhoid outbreak in a
British regiment.
Although the evidence that milk may not infrequently serve as an agent
in spreading disease is conclusive enough to satisfactorily prove the
proposition, yet it should be borne in mind that the organism of any
specific disease in question has rarely ever been found. The reasons for
this are quite the same as those that govern the situation in the case
of polluted waters, except that the difficulties of the problem are much
greater in the case of milk than with water. The inability to readily
separate the typhoid germ, for instance, from the colon bacillus, an
organism frequently found in milk, presents technical difficulties not
easily overcome. The most potent reason of failure to find disease
bacteria is the fact that infection in any case must occur sometime
previous to the appearance of the outbreak. Not only is there the usual
period of incubation, but it rarely happens that an outbreak is
investigated until a number of cases have occurred. In this interim the
original cause of infection may have ceased to be operative.
~Typhoid fever.~ With reference to the diseases likely to to be
disseminated through the medium of milk, infected after being drawn from
the animal, typhoid fever is the most important. The reason for this is
due (1) to the wide spread distribution of the disease; (2) to the fact
that the typhoid bacillus is one that is capable of withstanding
considerable amounts of acid, and consequently finds even in raw milk
containing the normal lactic acid bacteria conditions favorable for its
growth.[113] Ability to grow under these conditions can be shown not
only experimentally, but there is abundant clinical evidence that even a
slight infection often causes extensive outbreaks, as in the Stamford,
Conn., outbreak in 1895 where 386 cases developed in a few weeks, 97 per
cent. of which occurred on the route of one milk-man. In this case the
milk cans were thoroughly and properly cleaned, but were rinsed out with
_cold_ water from a shallow well that was found to be polluted.
The most common mode of pollution of milk with typhoid organisms is
where the milk utensils are infected in one way or another.[114] Second
in importance is the carrying of infection by persons serving in the
dual capacity of nurse and dairy attendant.
~Cholera.~ This germ does not find milk so favorable a nutrient medium as
the typhoid organism, because it is much more sensitive toward the
action of acids. Kitasato[115] found, however, that it could live in
raw milk from one to four days, depending upon the amount of acid
present. In boiled or sterilized milk it grows more freely, as the
acid-producing forms are thereby eliminated. In butter it dies out in a
few days (4 to 5).
On account of the above relation not a large number of cholera outbreaks
have been traced to milk, but Simpson[116] records a very striking case
in India where a number of sailors, upon reaching port, secured a
quantity of milk. Of the crew which consumed this, every one was taken
ill, and four out of ten died, while those who did not partake escaped
without any disease. It was later shown that the milk was adulterated
with water taken from an open pool in a cholera infected district.
~Diphtheria.~ Milk occasionally, though not often, serves as a medium for
the dissemination of diphtheria. Swithinbank and Newman[117] cites four
cases in which the causal organism has been isolated from milk. It has
been observed that growth occurs more rapidly in raw than in sterilized
milk.[118]
Infection in this disease is more frequently attributable to direct
infection from patient on account of the long persistence of this germ
in the throat, or indirectly through the medium of an attendant.
~Scarlet fever.~ Although it is more difficult to study the relation of
this disease to contaminated milk supplies, because the causal germ of
scarlet fever is not yet known, yet the origin of a considerable number
of epidemics has been traced to polluted milk supplies. Milk doubtless
is infected most frequently from persons in the earlier stages of the
disease when the infectivity of the disease is greater.
~Diarrhoeal diseases.~ Milk not infrequently acquires the property of
producing diseases of the digestive tract by reason of the development
of various bacteria that form more or less poisonous by-products. These
troubles occur most frequently during the summer months, especially with
infants and children, as in cholera infantum and summer complaint. The
higher mortality of bottle-fed infants[119] in comparison with those
that are nursed directly is explicable on the theory that cows' milk is
the carrier of the infection, because in many cases it is not consumed
until there has been ample time for the development of organisms in it.
Where milk is pasteurized or boiled it is found that the mortality among
children is greatly reduced. As a cause of sickness and death these
diseases exceed in importance all other specific diseases previously
referred to. These troubles have generally been explained as produced by
bacteria of the putrefactive class which find their way into the milk
through the introduction of filth and dirt at time of milking.[120]
Fluegge[121] has demonstrated that certain peptonizing species possess
toxic properties for animals. Recent experimental inquiry[122] has
demonstrated that the dysentery bacillus (Shiga) probably bears a causal
relation to some of these summer complaints.
~Ptomaine poisoning.~ Many cases of poisoning from food products are also
reported with adults. These are due to the formation of various toxic
products, generally ptomaines, that are produced as a result of
infection of foods by different bacteria. One of these substances,
_tyrotoxicon_, was isolated by Vaughan[123] from cheese and various
other products of milk, and found to possess the property of producing
symptoms of poisoning similar to those that are noted in such cases. He
attributes the production of this toxic effect to the decomposition of
the elements in the milk induced by putrefactive forms of bacteria that
develop where milk is improperly kept.[124] Often outbreaks of this
character[125] assume the proportions of an epidemic, where a large
number of persons use the tainted food.
FOOTNOTES:
[78] Hart, Trans. Int. Med. Cong., London, 1881, 4:491-544.
[79] Freeman, Med. Rec., March 28, 1896.
[80] Busey and Kober, Rept. Health Off. of Dist. of Col., Washington, D.
C., 1895, p. 299. These authors present in this report an elaborate
article on morbific and infectious milk, giving a very complete
bibliography of 180 numbers. They append to Hart's list (which is
published in full) additional outbreaks which have occurred since,
together with full data as to extent of epidemic, circumstances
governing the outbreak, as well as name of original reporter and
reference.
[81] Smith, Theo., Journ. of Expt. Med., 1898, 3:451.
[82] Dinwiddie, Bull. 57, Ark. Expt. Stat., June, 1899; Ravenel, Univ.
of Penn. Med. Bull., Sept. 1901.
[83] Ravenel, Journ. of Comp. Med. & Vet. Arch., Dec. 1897; Hartzell,
Journ. Amer. Med. Ass'n, April 16, 1898.
[84] Stille, Brit. Med. Journ., Aug. 19, 1899.
[85] This test is made by injecting into the animal a small quantity of
tuberculin, which is a sterilized glycerin extract of cultures of the
tubercle bacillus. In a tuberculous animal, even in the very earliest
phases of the disease, tuberculin causes a temporary fever that lasts
for a few hours. By taking the temperature a number of times before and
after injection it is possible to readily recognize any febrile
condition. A positive diagnosis is made where the temperature after
inoculation is at least 2.0 deg. F. above the average normal, and where
the reaction fever is continued for a period of some hours.
[86] Martin, Brit. Med. Journ. 1895, 1:937; Nocard, Les Tuberculoses
animales, 1895.
[87] C. O. Jensen, Milch Kunde und Milch hygiene, p. 69.
[88] Ostertag, Milch Zeit., 22:672.
[89] Obermueller, Hyg. Rund., 1897, p. 712; Petri, Arb. a. d. Kais. Ges.
Amte, 1898, 14: 1; Hormann und Morgenroth, Hyg. Rund., 1898, p. 217.
[90] Rabinowitsch, Zeit. f. Hyg., 1897, 26: 90.
[91] Th. Smith. Journ. of Expt. Med., 1899, 4:217.
[92] Russell and Hastings, 18 Rept. Wis. Expt. Stat., 1901.
[93] Hesse, Zeit. f. Hyg., 1900, 34:346.
[94] Practically all of the finest butter made in Denmark is made from
cream that has been pasteurized at temperatures varying from 160 deg.-185
deg. F.
[95] Gebhardt, Virch. Arch., 1890, 119:12.
[96] Scheurlen, Arb. a. d. k. Ges. Amte, 1891, 7:269; Bang, Milch Zeit.,
1893, p. 672.
[97] Moore, Year Book of U. S. Dept. Agr., 1895, p. 432.
[98] Weigel and Noack, Jahres. d. Ges. Med., 1890, p. 642; Weissenberg,
Allg. med. Cent. Zeit., 1890, p. 1; Baum, Arch. f. Thierheilkunde, 1892,
18:16.
[99] Schneider, Muench, med. Wochenschr., 1893, No. 27; Froehner, Zeit f.
Fleisch u. Milchhygiene, 1891, p. 55.
[100] Feser, Deutsche Zeit. f. Thiermed., 1880, 6:166.
[101] Nocard, Bull. Gen., 1885, p. 54.
[102] Deutsche Viertelsjahr. f. offentl. Gesundheitspflege, 1890,
20:444.
[103] Zeit. f. Fleisch und Milch hygiene, 11:114.
[104] E. Roth, Deutsche Vierteljahresschr. f. offentl. Gesundheitspfl.,
1890, 22:238
[105] S. W. North, London Practitioner, 1889, 43:393.
[106] Sedgwick and Chapin, Boston Med. & Surg. Journ., 1893, 129:485.
[107] Dabney, Phila. Med. News, 1893, 63:630.
[108] Welphy, London Lancet, 1894, 2:1085.
[109] Brit. Med. Journ., 1894, 1:815.
[110] Mass. Bd. Health Rept., 1894, p. 765.
[111] Turner, London Practitioner, 1892, 49:141; Munro, Brit. Med.
Journ., 1894, 2:829.
[112] Hankin, Brit. Med. Journ., 1894, 2:613.
[113] Heim (Arb. a. d. Kais. Gesundheitsamte, 1889, 5:303) finds it
capable of living from 20-30 days in milk.
[114] Schueder (Zeit. f. Hyg., 1902, 38:34) examined the statistics of
638 typhoid epidemics. He found 71 per cent. due to infected drinking
water, 17 per cent. to infected milk, and 3.5 per cent. caused by other
forms of food.
[115] Kitasato. Arb. a. d. Kais. Gesundheitsamte, 1:470.
[116] Simpson, London Practitioner, 1887, 39:144.
[117] Swithinbank and Newman, Bacteriology of Milk, p. 341.
[118] Schottelius and Ellerhorst. Milch Zeit., 1897, pp. 40 and 73.
[119] Baginsky, Hyg. Rund., 1895, p. 176.
[120] Gaffky, Deutsch. med. Wochen., 18:14.
[121] Fluegge. Zeit., f. Hyg., 17:272, 1894.
[122] Duval and Bassett, Studies from the Rockefeller Inst. for Med.
Research, 2:7, 1904.
[123] Zeit. f. physiol. Chemie, 10:146; 9 Intern. Hyg. Cong. (London),
1891, p. 118.
[124] Vaughan and Perkins, Arch. f. Hyg., 27:308.
[125] Newton and Wallace (Phila. Med. News, 1887, 50:570) report three
outbreaks at Long Branch, N. J., two of which occurred in summer hotels.