How Far May a Cow be Tuberculous 
Before Her Milk Becomes Danger- 
ous as an Article of Food? 
BY 
HAROLD C_ERNST, M. D., 
BOSTON. 
REPRINTED FROM 
THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES, 
November, 1889. Extracted from the 
American Journal of the Medical Sciences for November, 1889. 
HOW FAR MAY A COW BE TUBERCULOUS BEFORE 
HER MILK BECOMES DANGEROUS AS AN 
ARTICLE OF FOOD?1 
By Harold C. Ernst, A.M., M.D., 
OF BOSTON. 
The change of opinion in regard to the infectious nature of tubercu- 
losis has been very marked in the last few years, not among the scientists, 
but among the people at large. Of course the medical world has, as a 
rule, accepted the conclusions to be drawn from Villemin's work of 
twenty-five years ago, and the discovery of the specific cause of the 
disease by Koch has only added strength to the theories advanced in 
certain quarters before that time. 
The change of opinion spoken of is, after all, hardly a change, but, 
more properly, an acceptance of the knowledge gained in regard to the 
disease by the more recent and exact methods of research, and a much 
wider diffusion of that knowledge. More and more is it the rule that 
the knowledge of the transmissibility of tuberculosis by means of infected 
material is recognized among those whom it concerns the most, and 
nothing but good can come from the diffusion of that knowledge. 
It is hardly too much to say that proper methods of management of 
tuberculosis, both in human beings and in animals, involve more im- 
portant interests-pecuniary as well as vital - than any other subject 
that engages the attention of medical men. It is well known that one- 
seventh of the human race, approximately, perish from this disease, and 
when we acknowledge to ourselves, as a fair review of the evidence at 
hand must force us to do, that most, if not all, of this loss is preventable 
our duty is plain before us. That is, never to cease speaking of it, never 
to give up trying to reconcile the money interests of man with his own 
welfare, and to do all in our power, by the collection of clinical and 
experimental evidence, to make the case complete. 
The work showing the etiological relationship of the bacillus of tuber- 
culosis to the disease was, to all intents and purposes, complete upon the 
1 Read before the Association of American Physicians, Washington, Sept. 20, 1889. 2 
ERNST, TUBERCULOSIS AND COW'S MILK. 
publication of Koch's monograph upon the subject. Nothing more in 
the way of proof was actually needed, and, indeed, very little has been 
furnished. At the same time, confirmatory evidence was demanded by 
some who had and many who had not access to the original details, and 
this confirmatory evidence has been furnished in such overwhelming 
amount that it is to-day but a waste of time to repeat, what is accepted 
the scientific world over, that in the organism described by Koch we 
have the specific cause of this pathological change, and that without its 
activity we do not have tuberculosis in any form or under any conditions. 
An imperfect understanding of the nature of bacteria in general, and 
of this organism in particular, has led to many attempts to arrest the 
pulmonary form of the disease it produces, by therapeutic measures, 
most of which would have been seen to be useless at the outset, if a 
knowledge of the problem had been complete. It is not upon drugs or 
mechanical means that our reliance should be placed in attempting to 
stamp out this scourge of civilized man. Our attention must be turned 
in the direction of proper preventive measures, and until the necessity 
for this is impressed upon physicians in general, and by them upon the 
people at large, so that the preventive measures suggested after mature 
deliberation will be complied with, but little can be effected, and the 
knowledge gathered after so much hard labor must be considered as 
wasted, for the time being. 
In order to the suggestions upon which the stamping out of tubercu- 
losis must depend, there is necessary a large amount of investigation into 
the methods by which it spreads and by which the virus is carried from 
person to person. Among these methods are undoubtedly the excreta- 
more especially the sputum-from persons affected with the disease ; the 
excreta are carelessly treated and scattered broadcast to the injury of 
persons susceptible but not previously affected. The methods of distri- 
bution in this way, and the behaviour of the bacillus of tuberculosis out- 
side of the body, have been well and recently treated by Cornet (Zeit. f. 
Hyg., Bd. v. S. 191, 1888). 
Other methods of distribution are of importance, however, and until 
within a few years have not received attention from the medical profes- 
sion at all commensurate with their value. These methods of infection 
are those arising from the ingestion of food materials coming from the 
domestic animals, especially the flesh and milk of cattle. 
In Koch's Etiology of Tuberculosis he uses the following expressions : 
" Since by far the greatest number of cases of tuberculosis begin in the 
lungs, it is to be supposed that the infection in all these cases has taken place 
in the manner just suggested-by the inhalation of phthisic sputum dried 
and made into dust. The second principal source for the tubercle-bacilli, 
viz., tuberculosis of the domestic animals, appears not to have anything like 
the importance of the phthisic sputum. The animals, as is well known, pro- 
duce no sputum, so that during their life no tubercle-bacilli get from them ERNST, TUBERCULOSIS AND COW'S MILK. 
3 
into the outer world by means of the respiratory passages. Also in the excre- 
ment of tuberculous animals the bacilli appear to be only exceptionally 
present. On the contrary, it is a fact that the milk of tuberculous animals 
can cause infection. 
"With the exception of this one way, therefore (i.e., through milk), the 
tuberculous virus can only have effect after the death of the animal, and can 
only cause infection by the eating of the meat. The same conditions hold for 
the milk of cows suffering from ' perlsucht.' Before all things, if infection is 
to take place, it is necessary that the milk contain tubercle-bacilli; but this 
appears to be the case only when the milk-glands themselves are affected with 
the disease. This explains at once the contradictions in the statements of 
various authors, who have made feeding experiments with the milk from cows 
suffering from 'perlsucht.' If infection from tuberculous animals does not 
appear to be frequent, it must by no means be underrated." 
This caution is one which was necessary at the time it was written, 
and its repetition is as necessary now as ever. What conclusions may 
be reached in regard to its extreme importance, are well shown by the 
statistics collected and presented by Dr. Brush before the New York 
Academy of Medicine, on April 29, 1889 {Boston Med. and Burg. Journal, 
cxx. p. 467 et seq.). In this paper the author states that after several 
years of close study of the affection, including a consideration of all 
accessible statistics, and the habits of the people among whom it prevails, 
he has arrived at the conclusion that the only constantly associated factor 
is found in the in-bred bovine species. If a community was closely con- 
nected with in-bred dairy cattle, tuberculosis prevailed, and, vice versd, 
if there were no in-bred dairy cattle there was no tuberculosis. In the 
discussion following this paper many objections were raised. Dr. Brush 
went on to say that he believed that the disease was originally derived 
from the bovine species. He did not believe that less than fifty per 
cent of all dairy cattle were affected with it, while the statistics he had 
quoted showed that wherever there was a race of people without cattle 
phthisis was unknown. He believed, furthermore, that if all the cattle 
in this country were to be killed, the disease would finally die out 
entirely here. 
Such statements as these are a revelation to the generality of practi- 
tioners, and may seem to be somewhat forced, but they certainly indi- 
cate, together with the statistics upon which they are based, the existence 
of a greater danger than has been fairly realized. That the danger from 
the consumption of milk coming from cows affected with tuberculosis 
has been understood by individuals at least, and that, too, before the 
announcement of Koch's discovery, is very well shown by extracts from 
a letter which I take the liberty of quoting here. The gentleman 
writing it is a veterinarian in practice in Providence, R. I., and the 
observations were made and the advice given more than ten years ago. 
That portion of his letter bearing upon the subject in hand is as follows : 
" Mr. W., June 15, 1878, called me to see a white and red cow. Coughs 
and is short of breath and wheezes. Pulse 60; respiration 14, and heavy at 4 
ERNST, TUBERCULOSIS AND COW'S MILK. 
the flanks ; temperature 104°. Diminished resonance of right lung, but in- 
creased in part of the same. Emphysematous crackling over left lung and 
dulness on percussion. Diagnosed a case of tuberculosis and advised the 
destruction of the animal. 
" Dec. 12. Cow in a cold rain a few days ago for about two hours. Milk 
still more diminished than at a visit made on September 25th. Again advised 
the destruction of the cow. Family still using the milk. Respiration 20; 
pulse 85 ; temperature 104.6°. 
"Feb 22,1879. Temperature 104.8° ; respiration 26 ; pulse 68. Losing flesh 
fast. Milk still in small quantities. Advised, as before, to destroy the animal 
and not to use milk. 
"May 30. Called in a hurry to see cow. Is now as poor as could be. No milk 
for a week. Pulse 80 ; respiration 40 ; temperature 106°. The cow died in 
about three hours. Autopsy made fourteen hours after death: Lungs infil- 
trated with tuberculous deposit. Weight of thoracic viscera 43.5 pounds. 
Tuberculous deposits found in the mediastinum, in the muscular tissues, 
and in the mesentery, spleen, kidneys, udder, intestines, pleura, and one 
deposit on the tongue. The inside of the trachea was covered with small 
tubercles. 
"In August, 1879, the baby was taken sick,and died in about seven weeks. 
On post-mortem of the child there was found meningeal tuberculosis-deposits 
all over the coverings of the bruin and some in the lung. 
"In 1881 a child, about three years old, died with, as it was called, tuber- 
culous bronchitis. And in 1886, a boy, nine years old, who for three or four 
years had been delicate, died with consumption-'quick,' as it was called. 
"So far as known, the family on both sides have never before had any 
trouble of the kind, and the parents were both rugged and healthy people, 
and so were the grandparents-one now being alive and sixty-eight years old, 
and the other dead at seventy-eight." 
Of course there is much room for criticism, if these cases be quoted as 
carrying out an exact clinical experiment, and no one can say that the 
occurrence of the three deaths in the same family was anything more 
than a coincidence. At the same time it must be acknowledged that 
they offer very solid suggestions for consideration, and that the light 
thrown upon the disease by the investigations of recent years make the 
advice of the veterinarian to " kill the cowand stop using the milk" 
much more sound than it appeared to the minds of the medical gentle- 
men who "laughed" at him at the time it was given. 
It is my hope within the coming year to collect a series of clinical 
observations which will be of interest and some service in elucidating 
the question of how many cases of tuberculosis occur which produce 
suspicion in the minds of medical or veterinary attendants of having an 
origin in the milk from infectious cows. 
It is upon this question of possible danger from the domestic animals 
-especially cattle-that much recent work has been done, but the sub- 
ject has been by no means exhausted. 
If there is danger to human beings from the widespread existence of 
tuberculosis among cattle, some sort of restrictive measures must be 
taken, by means of which this danger can be lessened. At the same 
time legislation calling for so much pecuniary loss as would be the case 
if the present supply of tuberculous cattle wrere to be destroyed, can ERNST, TUBERCULOSIS AND COW'S MILK. 
5 
only be asked for with a backing of as much carefully gathered scien- 
tific evidence as can be obtained, and it is the part of preventive medi- 
cine and the experimental method to furnish some of this evidence. 
Through the liberality and broad-mindedness of an association of 
gentlemen in Boston, it is possible to present the results of certain ex- 
periments undertaken to determine the question which is expressed in 
the title of this paper. " How far may a cow be tuberculous before her 
milk becomes dangerous as an article of food ? " is an extremely im- 
portant point to decide. If it be considered already settled and Koch's 
dictum be accepted, that there is no danger in the milk, if the mam- 
mary glands be not affected, then there remains only for the veterinary 
surgeon to determine the existence of such lesions, and restrictive meas- 
ures can go no further. If, however, the milk from cows with no visible 
lesion of the lacteal tract be shown to contain the specific virus of the 
disease in a not inconsiderable number of cases, and if this milk be 
shown to possess the power of producing the tuberculous process upon 
inoculation in small quantities and in feeding experiments carried out 
with every possible precaution, then restrictive measures must have a 
far wider scope, and be carried on from an entirely different standpoint 
than has heretofore been considered necessary. 
It is familiar to most of us that little importance has been attached 
to this question-the danger of milk from tuberculous cows with no 
lesions of the udder-for the reason that many experiments have been 
made with negative results, and because a priori reasoning would seem 
to indicate the absence of such danger; because tuberculosis is not a 
disease like anthrax, in which the specific poison is to be found in all 
parts of the system and is carried from one place to another by the 
blood-stream. Koch's assertion that the milk from cows affected with 
tuberculosis is dangerous only when the udder is involved, appears to be 
based upon theoretical considerations rather than practical work in this 
especial direction. It has been widely accepted, however, and the 
weight of his name has caused the assertion to be repeated many times 
with but few attempts to verify its correctness. 
The increased attention that has been paid to the disease among 
cattle, and the suspicions that have been aroused that tuberculosis 
among the domestic animals is a more frequent cause of its appearance 
among men than has been supposed, have made a careful investigation 
of this point imperatively necessary. With the exception of a few suc- 
cessful experiments by Bollinger {Deutsch. Zeit. f. Thiermed., Bd. xiv. 
S. 264) and Bang {Ibid., Bd. 11, S. 45, 1885), no evidence of great 
value is to be adduced. These authors, as well as Tschokke (quoted by 
Bollinger), bring out isolated cases showing successful inoculation ex- 
periments with the milk from tuberculous cows with no disease of the 
udders, but the experiments are so few in number that they cannot be 6 
ERNST, TUBERCULOSIS AND COW'S MILK. 
accepted as furnishing more than a probability, and extremely critical 
persons might be justified in ascribing the results to contamination. 
Bang ( Congrls pour Vetude de la Tuberculose, 1, p. 70,1888) gives new 
results. Examining twenty-one cases of cows affected with general 
tuberculosis but with no signs of disease in the udder, he found but two 
whose milk showed virulent qualities upon inoculation in rabbits. He 
concludes that since the cows experimented with were in advanced 
stages of the disease and yet showed such slight virulent properties in 
their milk, the danger from cows in less advanced stages is much less. 
And this conclusion he thinks is borne out by experiments with milk 
drawn from eight women affected with tuberculosis; specimens were used 
from all for inoculation and none were found to be virulent. He draws 
the conclusion, therefore, that it is not necessary to consider all milk 
dangerous coming from tuberculous cows, but that it should always be 
suspected, because no one can say when the udder will be diseased, and 
because, without this, the milk from tuberculous cows contains the virus 
in rare cases. 
I shall endeavor to show that it is not at all rare for such milk to 
contain the virus. 
Galtier also (loc. tit., p. 81) has given the result of certain experi- 
ments with milk coming from tuberculous cows, but he says that 
" certain experimenters claim to have established the virulence of milk coming 
from animals whose udders appeared to be normal and free from any lesions; 
the greater number, and I am one of them, have merely encountered a viru- 
lence in milk after the udder had become tuberculous. However, as a begin- 
ning tuberculosis of the udder is an extremely difficult thing to recognize, 
especially during the life of the animal, the milk should be considered dan- 
gerous which comes from any animal affected, or suspected of being affected, 
with tuberculosis." 
I shall endeavor to show that this view of the case is justified by 
something more than probabilities. 
In the Deutsch. Arch, far kiln. Med., Bd. xliv. S. 500, Hirschberger 
reports the results of an experimental research upon the infectiousness 
of the milk of tuberculous cows, in which-following out Bollinger's 
work-he attempts to settle, 1st, whether the cases are rare in which 
tuberculous cows give an infectious milk; and 2d, whether the milk is 
infectious only in cows with general tuberculosis, or whether it is also 
infectious when the disease is localized. He made the trials of the in- 
fected milk by injection into the abdominal cavity of guinea-pigs with 
the usual precautions. His results were as follows: 
1. Milk was used five times from cows affected with a very high 
degree of general tuberculosis in all the organs. 
2. Milk was used six times from cows with only a moderate degree of 
disease. EKNST, TUBERCULOSIS AND COW'S MILK. 
7 
3. Milk was used nine times from cows in which the disease was 
localized in the lung. 
From these twenty cases the milk was proven to be infectious in 
eleven. The percentage of positive results in the animals when arranged 
in accordance with the three groups above given was 80 per cent, in the 
first group (milk from cows in a very advanced stage of the disease), 66 
per cent, in the second group, and 33 per cent, in the third. He found 
the bacilli in only one of the specimens of the milk, and considers that 
this, therefore, shows that the inoculation experiments are the more cer- 
tain guide as to whether the milk is infectious or not. 
These results are extremely interesting, although they do not lay as 
much stress as do mine upon the presence or absence of lesions of the 
lacteal tract. 
The experiments which I am able to report1 have been made possible 
by the liberality of the Massachusetts Society for the Promotion of 
Agriculture, which became interested in the question some time ago, and 
has put it in my power to carry them on. They have given everything 
in the way of pecuniary and moral support that the work has required; 
my own part has been that of general director, and I have had asso- 
ciated with me during the whole time the Society's veterinarian, Austin 
Peters, D. V. S. For the last year I have also had the very valuable 
aid of Dr. Henry Jackson and Langdon Frothingham, M. D. V. 
All of the inoculation experiments and most of the microscopic work 
have been done in the bacteriological laboratory of the Harvard Medical 
School, some of the microscopic work at the Society's laboratory in 
Boston, whilst the feeding experiments have been done and the experi- 
mental animals have been kept at a farm in the country devoted to this 
especial purpose, and situated among the healthiest possible surround- 
ings. Nothing has been set down as the result of microscopic observa- 
tion that I have not myself verified, and every portion of the work has 
been carried out under the most exacting conditions and with every 
possible precaution against contamination. 
Before the farm buildings were used at all they were thoroughly 
cleaned from top to bottom. Every portion of old manure was carted 
away, as well as all the old earth. The whole of the woodwork was 
scrubbed and then washed with corrosive sublimate solution (1:1000) 
and finally whitewashed, and every care was taken to secure good drain- 
age and free ventilation. The result and effectiveness of all this have 
been best demonstrated by the fact that every animal brought to the 
place made a most marked improvement in its general condition, while 
some of them even went so far as to appear to get well. 
1 The full notes of these experiments will be found in the Transactions of the Associa- 
tion of American Physicians, vol. iv., 1889. 8 
ERNST, TUBERCULOSIS AND COW'S MILK. 
In deciding whether the milk from any cow affected with tuberculosis 
is dangerous, when the udder shows no lesion, the first point is to see 
whether the milk contains the infectious principle or not. In this case, 
of course, that infectious principle is the bacillus of tuberculosis, and 
attention was turned to that for some time. The observations have been 
carried on over a long space of time, and were made as follows : The 
milk was taken from the cow in the morning -or evening, as the case 
might be-the udders and teats having just been thoroughly cleansed. 
The receptacle was an Erlenmeyer flask, stoppered with cotton-wool and 
thoroughly sterilized by heat. The specimen was taken at once to the 
laboratory, there placed n conical glasses, with ground-glass covers- 
the whole of these having been carefully cleansed beforehand-and 
then allowed to stand in a clean refrigerator for twenty-four to forty- 
eight hours, and sometimes for seventy-two hours. 
At the end of that time from ten to twenty cover-glass preparations 
were made from various parts of the milk or cream. These were stained 
after Ehrlich's twenty-four hour method, with fuchsin and methylene 
blue as a contrast color, and then searched with an immersion lens. 
We prepared for examination in the way spoken of above, one hun- 
dred and seventeen sets of cover-glasses from as many different samples 
of milk. Of these specimens three spoiled, i. e., turned sour or acid 
before the examination was completed, and must be rejected, leaving, 
therefore, one hundred and fourteen samples of milk of which the ex- 
amination was completed. These samples were obtained from thirty-six 
different cows, all of them presenting more or less distinct signs of 
tuberculosis of the lungs or elsewhere, but none of them having marked 
signs of disease of the udder of any kind. 
Of these samples of milk there were found seventeen in which the 
bacilli of tuberculosis were distinctly present; that is to say, the actual 
virus was seen in 31.5 per cent, of the samples examined (36:114 
=31.5). These seventeen samples of infectious milk came from ten 
different cows, showing a percentage of detected infectiousness of 27.7 
per cent. (10: 36=27.7). These results are exceedingly interesting, it 
seems to me, and I confess I am surprised at the size of the percentage 
named. Not because I had not expected to find the bacilli-I have 
been convinced for several years that persistent search would show their 
presence in such cases as those that are here recorded-but because the 
amount of dilution to which the organisms must be subjected dimin- 
ished immensely the chance of their being found at all. In no case 
have they been seen in large numbers, but equally in no case has a 
diagnosis been made where there was the slightest doubt of the appear- 
ances under the microscope. 
The large number of cases in which these organisms have been found 
seem to me to indicate their presence in a still greater proportion of ERNST, TUBERCULOSIS AND COW'S MILK. 
9 
cases, if only a sufficiently thorough examination of all the milk could 
be made. This of course is out of the question, but the results here 
given seem to establish, beyond a doubt, the fact that milk coming from 
cows with no definite lesion of the udder may contain the infectious 
principle of tuberculosis, if the disease be present in other portions of 
the body of the animal. Also, that this presence of the infectious prin- 
ciple is not merely a scientific possibility but an actual probability, which 
we should be thoroughly aware of and alive to. 
Other interesting facts shown are these: that the cream after rising is 
quite as likely to be infectious as the milk, because the bacilli were 
found in the milk nine times after the cream had risen, and in the 
cream eight times after it had separated from the milk. 
In regard to the constancy of the occurrence of the bacilli in the 
milk, in two of the ten cows in whose milk the bacilli were found, but 
one sample of the milk was examined; and the bacilli were found in 
one sample out of several examined at different times, in two cases. In 
the remaining six cows, bacilli were found two or more times in different 
samples of the milk. So that, as far as they go, these results seem to 
indicate that the bacilli are present with a fair degree of constancy. 
At the same time it should not be surprising if one examination was 
successful and others failed, because of the chances against success, 
owing to dilution, which were spoken of above. 
In nine of the seventeen cases the time of the milking and the por- 
tion of the milk used were noted ; that is to say, a sample was taken 
from the first of the milking, or the last of the milking, and then cover- 
glasses made from the milk or cream. In these cases bacilli were found 
in the cream three times, and in the milk four times, from the first of 
the milking; in samples from the last of the milking, in the cream no 
times, and in the milk four times; and this too seems to show an inter- 
esting point, viz., that the bacilli, if present at all in the udder, are not 
washed out entirely by the first manipulations of the teats, but may be 
supposedly present in any portion of the milk. The converse is also 
indicated, that the manipulation of the udder in the process of milking 
does not express the bacilli from the tissue into the latter portion of the 
milk, but that, as before, they may be supposed to be pretty evenly dis- 
tributed in all parts of the udder if they be present at all. 
Before going on to consider the results of the inoculation experiments 
made with various specimens of milk, it may be well to glance at the 
condition of the cows that have been under our control from the time of 
the beginning of the experiments until they were killed, or until the 
date of preparing this paper. 
The history of each cow, as far as we have been able to secure it, bears 
out our assertion-as far as the examinations have gone, that none of 
the udders were affected with tuberculosis-certainly so far as gross 10 
ERNST, TUBERCULOSIS AND COW'S MILK. 
appearances were concerned. This was true, also, in the microscopic 
appearance of every case but one (No. 6, cow F). In this case the 
gross appearances in the udder were healthy, except that one quarter 
seemed to be slightly fibrous, and there were one or two yellow spots 
which were seen to be made up of fat under the microscope. With a 
low power lens only a slight increase of fibrous tissue was observable, 
and the oil-immersion was put on merely as a matter of routine. One 
giant cell was discovered containing a number of bacilli, but a careful 
search failed to show any others, or any signs of change, except the 
increase of fibrous tissue noted above. So that the assertion is still true, 
that we have failed to discover any signs of tuberculosis that were easily 
recognizable in any of the cows here recorded, and these include all we 
have had under closer observation. 
Those from which milk was used for inoculations that are not here 
given had no signs that permitted of even a probable diagnosis by skilled 
veterinarians. 
We also made an interesting series of experimental inoculations in 
rabbits and guinea-pigs with milk or cream from various cows, in vary- 
ing quantities and at different times. Of rabbits there were used fifty- 
seven animals. Of these, five were inoculated with milk which had turned 
sour, two died of intercurrent diseases in a few days (coccidium ovi- 
forme), and of one the material was lost before the microscopic examina- 
tion was completed-so that eight animals are to be rejected, leaving 
forty-nine upon which the results can be based. Out of these, five were 
made more or less tuberculous, as proven by microscopic examination, 
and in forty-four the results were negative-that is to say, we obtained 
5 : 49, or 10.2 per cent, of successes out of all inoculations in rabbits. 
There were used thirty-three different specimens from thirteen different 
cows-that is, there were 23 per cent. (3:13) successful results from the 
cows used, and 15.15 per cent. (5 : 33) successful results from the speci- 
mens used. 
Positive results were obtained from 
Cow P twice (at different times). 
Cow L once. 
Saunders cow twice (at different times). 
The results of the inoculations of guinea-pigs are more striking. There 
were sixty-five animals used in all. Of these, nine were inoculated with 
sour milk or cream, and two died in a day or two of other diseases (peri- 
tonitis and pleurisy). There are, therefore, but fifty-four that should 
be counted. In them, there were twelve positive results, or 28.57 per 
cent. (12:42) successes out of all the inoculations. There were used 
thirty-two specimens from fourteen different cows, and the successful 
results came from six different cows-that is, 42.8 per cent. (6 : 14) of 
the cows were shown in this way to have infectious milk, and 37.5 per ERNST, TUBERCULOSIS AND COW'S MILK. 
11 
cent. (12 : 82) of the specimens used were show n to have active infectious 
properties. 
Positive results W'ere obtained from 
Cow P (three times in two different inoculations). 
Cow D (three times in three different inoculations). 
Cow F (once). 
Slocum cow (once). 
Saunders cow7 (once). 
Mayhew cow (three times in two different inoculations). 
The combining of the results obtained from both rabbits and guinea- 
pigs shows the following: Successful results w7ere obtained in milk from 
cow P three times (two different specimens) in guinea-pigs, and twice in 
rabbits (two different specimens) ; from cow L once in rabbits ; from cow 
O three times (three different specimens) in guinea-pigs; from cow F 
once in guinea-pigs; from the Slocum cow once in guinea-pigs; from 
the Saunders cow once in guinea-pigs, and twice in rabbits (two different 
specimens); and from the Mayhew cow three times in guinea-pigs (two 
different specimens)-that is to say, out of fourteen cows used the milk 
was shown to be infectious in seven, or 50 per cent., by inoculation ex- 
periments. 
An interesting fact is also shown, and that is, that bacilli w'ere found 
in the milk or cream, and successful inoculation experiments made in 
animals with the same specimen in five different cases (including eight 
of the successful ones) as follows: 
Comparison of the dates ivhen Bacilli were found in the Milk and the same Milk 
was used for successful inoculation experiments. 
Cow. Positive. Positive. Positive. 
Cover-glass. Guinea-pig. Rabbit. 
P. Cream, a. M. Cream, a. m., March 9,1889 Cream, a. m., March 9, 1889 
„ „ j Cream, p. m., March 9,1889 Cream, p. m., March 9,1889 
cream, p. m. j Cream, p. M., March 9, 1889 
O. First of milking, cream, First of milking, cream, 
March 9, 1889. March 9, 1889 
Slocum. Last of milking. Last of milking, 
June 10, 1889 
Mayhew. Last of milking, milk. Last of milking, milk, 
June 21, 1889 
The inoculation experiments, above detailed, seem to me to be deserv- 
ing of consideration because they were done under the most careful 
precautions that could be devised. In all cases the experiment animals 
were kept under observation long enough to determine, so far as could 
be seen, that they were in good health, and after the inoculations they 
w7ere separated and kept under close watch, but in healthy surroundings. 
Some of those that were used w7ere inoculated immediately after pur- 
chase, because of a scarcity of the supply at the farm, and were not in 
good condition. But as no sign of tuberculosis appeared in any of these, 
their ill health cannot come in as a disturbing factor in the results. 12 
ERNST, TUBERCULOSIS AND COW'S MILK. 
The results obtained from certain feeeding experiments with calves 
show that there were thirteen calves used, and fed for varying lengths 
of time with milk from cows affected with tuberculosis, but not of the 
udder. Of these, the material was thrown away from one before the 
microscopic examination, and this should be rejected in the final results. 
Of the remainder there were five positive results obtained and one sus- 
picious. The latter is counted as negative, for the reason that, although 
giant cells and granulation tissue were seen, no bacilli were found. 
There were, therefore, five out of twelve positive results, or 41.66 per 
cent. It should also be said that of those counted as negative three 
sets of specimens were suspicious, but were hastily examined for the pur- 
poses of this paper, so that a more careful search may very probably 
increase the percentage of successes. 
In the series of feeding experiments on one set of pigs, the milk being 
given to them from the same cows as before, there were seven pigs 
used in all, from one litter and healthy parents. Of these, examination 
showed negative results in two, positive results in two, one was subjected 
to a very hasty microscopic examination, and the material from two was 
thrown away-a mistake, as was shown by the results of the microscopic 
examination of the material from No. 3. There are to be counted, there- 
fore, only five, giving as successful results 40 per cent. 
By the cover-glass examinations we have shown that the milk contains 
infectious material in ten cows out of thirty-five from which the milk 
was examined for bacilli-that is, in 28.57 per cent. We have also 
shown that the milk was infectious, by inoculation experiments, in seven 
out of fourteen of the cows from which the milk came-that is, 50 per 
cent. And we have shown the infectious nature of the milk by ocular 
demonstration and successful inoculation from the same specimens in five 
cows out of fourteen used-or, 35.7 per cent. 
These results are, to a certain extent, preliminary-that is to say, 
they are but part of the work upon this subject which is being done 
under the auspices of the Massachusetts Society for the Promotion of 
Agriculture. The work will not be completed, at any rate, until next 
year. 
They show, however: 
1st, and emphatically, that the milk from cows affected with tubercu- 
culosis in any part of the body may contain the virus of the disease. 
2d. That the virus is present whether there is disease of the udder or 
not. 
3d. That there is no ground for the assertion that there must be a 
lesion of the udder before the milk can contain the infection of tubercu- 
losis. 
4th. That, on the contrary, the bacilli of tuberculosis are present and 
active in a very large proportion of cases in the milk of cows affected 
with tuberculosis but with no discoverable lesion of the udder. THE AMERICAN JOURNAL 
OF THE MEDICAL SCIENCES. 
the first issue for 1890, The American Journal of the Medical 
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