U. S. DEPARTMENT OF AGRICU
BUREAU OF ANIMAL INDUSTRY. BuLLETlNto. 86.
A. D. MELVIN, CHIEF OF BUREAU. fi C/, A^H J[ f>
EXPERIMENTS WITH MILK ARTIFICIALLY
INFECTED WITH TUBERCLE BACILLI.
BY
E. C. SCHROEDER, M. D. V.,
Superintendent of Experiment Station,
Bureau of Animal Industry,
W. E. COTTON,
Expert Assistant at Experiment Station,
Bureau of Animal Industry.
f California
Regional
Facility
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1906.
ORGANIZATION OF THE BUREAU OF ANIMAL INDUSTRY.
Chief: A. D. MELVIN.
Assistant Chief: A. M. FARRINGTON.
Chief Clerk: E. B. JONES.
Dairy Division: ED. H. WEBSTER, chief; CLARENCE B. LANE, assistant chief.
Inspection Division: RICE P. STEDDOM, chief; MORRIS WOODEN, assistant chief.
Quarantine Division: RICHARD W. HICKMAN, chief.
Animal Husbandman: GEORGE M. ROMMEL.
Editor: JAMES M. PICKENS.
Artist: W. S. D. HAINES.
Librarian: BEATRICE C. OBERLV.
LABORATORIES.
Biochemic Division: MARION DORSET, chief.
Pathological Division: JOHN R. MOHLER, chief.
Zoological Division: BRAYTON H. RANSOM, scientific assistant in charge.
EXPERIMENT STATION.
E. C. SCHROEDER, superintendent ; W. E. COTTON, assistant.
MEAT INSPECTION.
Inspectors in charge.
Austin, Minn. Dr. M. O. Anderson, care George
A. Hormel & Co.
Baltimore, Md. Dr. H. A. Uedrick, 215 St. Paul
street.
Bloomington, 111. Dr. Frederick Braginton, cara-
Continental Packing Company.
Boston, Mass. Dr. J. F. Ryder, 141 Milk street.
Brightwood, Mass. Dr. W. J. Murphy, care
Springfield Provision Company.
Buffalo, N. Y. Dr. B. P. Wende, Live Stock Ex-
change Building, East Buffalo.
Cedar Rapids, Iowa. Dr. T. A. Shipley, care T. M.
Sinclair & Co.
Chicago, 111. Dr. S. E. Bennett, room 316 Ex-
change Building, Union Stock Yards.
Cincinnati, Ohio. Dr. A. G. G. Richardson, care
Union Stock Yards.
Cleveland, Ohio. Dr. E. P. Schafftcr, care Cleve-
land Provision Company.
Davenport, Iowa. Dr. E. L. Bertram, care Henry
Kohrs Packing Company.
Denver, Colo. Dr. W. E. Howe, care Western
Packing Company.
Des Moines, Iowa. Dr. A. B. Morse, care The
Agar Packing Company.
Detroit, Mich. Dr. L. K. Green, care Hammond,
Standish & Co.
Eau Claire. Wis. Dr. G. W. Butler, care Drum-
mond Brothers.
Fort Worth, Tex. Dr. A. II. Wallace, care Swift
&Co.
Hutchinson, Kans. Dr. J. E: Blackwell, care
Ilutchinson Packing Company.
Indianapolis, Ind. Dr. N. C. Sorensen, care Kin-
gjin <V Cn.
Jersey City, N. J. Dr. Julius Huelsen, care The
Jersey City Stock Yard Company.
Kansas City, Kans. Dr. L. R. B'aker, room 338
Live Stock Exchange.
Los Angeles, Cal. Dr. A. E. Rishel, care Cudahy
Packing Company.
Louisville, Ky. Dr. II. 11. George, 507 Johnson
street.
Mankato, Minn. Dr. II. H. Dell, care Macbeth &
Gardner.
Marahiilltown, Iowa. Dr. J.O. F. Price, care Brit-
tain & Co.
Mason City, Iowa. Dr. Robert Jay, care Jacob E.
Decker A, Huns.
Milwaukee, Wis. Dr. A. E. Behnke, room 432
Federal Building.
Nashville, Tenn. Dr. W. B. Lincoln, care Tennes-
see Packing and Provision Company.
National Stock Yards, 111. Dr. J. B. Clancy.
Nebraska City, Nebr. Dr. W. II. Gibbs, care
Morton-Gregson Company.
Newark, N. J. Dr. Thomas Castor, care Swift &
Co., Harrison Station.
New Haven, Conn. Dr. Albert Long, care Sperry
& Barnes.
New York, N. Y. Dr. H. N. Waller, 109 West
Forty-second street.
Ottumwa, Iowa. Dr. Joshua Miller, care John
Morrell & Co.
Philadelphia, Pa. Dr. C. A. Schaufler, 134 South
Second street.
Pittsburg, Pa. Dr. F.W.Ainsworth, Union Stock
Yards.
Portland, Oreg. Dr. Clarence Loveberry, room
402 Custom-House (new) .
Quincy, 111. Dr. J. S. Kelly, care Blomer &
Michael Co.
St. Louis, Mo. Dr. J.J. Brougham, care Missouri
Stock Yards Company.
San Diego, Cal. Dr. Robert Darling, care Charles
S. Hardy.
San Francisco, Cal. Dr. George S. Baker, Sixth
and Townsend streets.
Seattle, Wash. Dr. O. B. Hess, care Frye-Bruhn
Company.
Sioux City, Iowa. Dr. G. A. Johnson, Exchange
Building.
South Omaha, Nebr. Dr. Don C. Ayer, Post-
Office building.
South St. Joseph, Mo. Dr. George Ditewig.
South St. Paul, Minn. Dr. F. D. Ketchum.
Tacoma, Wash. Dr. E. C. Joss, care Carstens
Packing Company.
Topeka, Kans. Dr. F. L. De Wolf, care Charles
Wolff Packing Company.
Waterloo, Iowa. Dr. T. W. Scott, care The Ka I h
Packing Company.
Wichita, Kans. Dr.W. N. Neil, care John Cudiihy
Company.
Worcester, Mass. Dr. E. P. Dowd, care White,
Pevey & Dexter Co.
(Concluded on p. 3 of cover.)
U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ANIMAL INDUSTRY. BULLKTIN No. 80.
A. D. MHLVIN. CHIHK OK BUREAU.
E. C. SCHROEDER, M. 1). V.,
Superintendent of Experiment Station,
Bureau of Animal Industry,
AND
W. H. COTTON.
Expert Assistant at /Experiment Station,
Bureau of Animal Industry .
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
l0o.
LETTER OF TRANSMITTAL.
U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ANIMAL INDUSTRY,
Washington, D. C., May 19, 1906.
SIR : I have the honor to transmit herewith, and to recommend for
publication as a bulletin in the series of this Bureau, a manuscript
entitled "Experiments with Milk Artificially Infected with Tubercle
Bacilli," by Dr. E. C. Schroeder and W. E. Cotton, of the Experi-
ment Station of this Bureau. The work consisted of feeding and
inoculation experiments with guinea pigs and hogs, and was under-
taken to gain more definite information concerning the danger of
contracting tuberculosis through the ingestion of milk containing
tubercle germs.
This work throws new light upon the tuberculosis problem and is
especially important in its bearing on the supposition that the most
common way of contracting the disease is through the respiration.
The authors conclude that the great frequency of lung tuberculosis
need not be wholly ascribed to that form of exposure, but that the
lung may and does become infected when the bacilli enter the system
in other ways. Special attention is directed to the danger of infection
by tuberculous material taken into the body with the food.
Respectfully,
A. D. MELVIX,
Chief of Bureau.
Hon. JAMES WILSON,
Secretary of Agriculture.
CONTENTS.
An experiment with guinea pigs o
Plan of the experiment 5
The infectious material o
Methods of infecting the animals (i
Results of feedings and injections (i
The susceptibility of guinea pigs to tuberculosis
Distribution of lesions in the guinea pigs {>
A subcutaneous-inoculation experiment with hogs 10
Hogs inoculated with culture No. 1 11
Hogs inoculated with culture No. 2 , 11
Hogs inoculated with culture No. 3 . . 12
Hogs inoculated with culture No. 4 13
Distribution of lesions in the hogs . 13
Susceptibility of the lung to infection other than by respiration 14
Tests showing how the lung filters the blood 15
Spread of infection to other organs 16
Remarks on the hog inoculations 16
New significance of lung infection 17
Resistance of tubercle germs 18
Summary ... 19
EXPERIMENTS WITH MILK ARTIFICIALLY INFECTED
WITH TUBERCLE BACILLI.
AN EXPERIMENT WITH GUINEA PIGS.
Some of the work done recently at the Experiment Station with milk
from tuberculous cattle gave results which indicate that the danger
of contracting tuberculosis through the ingestion of milk, while it does
exist and should be guarded against, is of secondary importance com-
pared with other modes of infection. In order to gain more definite
information on the subject, an experiment was made in which a num-
ber of guinea pigs were exposed to infection with tuberculosis through
milk from normal, healthy cows to which cultures of tubercle bacilli
had been added. A detailed account of the experiment follows.
PLAN" OF THE EXPERIMENT.
THE INFECTIOUS MATERIAL.
A virulent culture of tubercle bacilli on agar was obtained from the
Pathological Division of this Bureau, and a portion of the surface
growth was scraped off and suspended in sterile water. The watery
suspension contained a sufficient amount of infectious material in a
finely divided state to give it a homogeneous, well-marked, cloudy
appearance. As much material as would cling to a fine platinum wire
loop the wire about one-fourth mm. and the loop about 2 mm. in
diameter was transferred from the suspension to fresh normal
milk at the rate of one loop per 10 c. c. of milk, and this milk was desig-
nated " Infection, degree A. ' ' From the original watery suspension one
loop of material was added to 10 c. c. of sterile water and material from
the sterile water to fresh .normal milk at the rate of one loop per 1 c. c.
of milk, and this milk was designated " Infection, degree B." Again,
from the original watery suspension one loop of material was added
to 100 c. c. of sterile water and material from the sterile water added
to fresh normal milk at the rate of one loop per 10 c. c. of milk, and
this milk was designated "Infection, degree C."
During the experiment four separate agar cultures of tubercle
bacilli were used, all strongly virulent for guinea pigs, and all made
from the same stock culture in the Pathological Division. The cul-
6 EXPERIMENTS WITH INFECTED MILK.
tures were 30 days old at the time they were used, and were received
at this station on the following dates, one culture on each day: July
13, July 21, July 27, and August 9. The suspension of tubercle bacilli
in water obtained from each culture was used daily to infect the milk,
as before described, until a fresh culture was received, when a fresh
watery suspension was made and the old one discarded.
METHODS OF INFECTING THE ANIMALS.
Milk of each of the three degrees of infectiousness was used for
injecting and feeding, some of the guinea pigs being injected, intra-
abdominally, some fed one day, and some fed thirty days.
Before the feeding was begun the guinea pigs were deprived of food
and drink for a period of twenty-four hours in order to induce them to
take a large quantity of the infected milk. The guinea pigs fed one
day received nothing but infected milk after the period of starvation
until they had each consumed 50 c. c., and the guinea pigs fed thirty
days were deprived of all drink but infected milk during the whole
period and consumed an average of 60 c. c. each per day. The average
daily amount of milk taken by the 30-day guinea pigs is large, because
the little animals soon learn to like milk very much and then drink it
eagerly the moment it is placed before them.
The amount of infected milk used for injecting was 5 c. c. for each
guinea pig.
Cover-glass preparations from milk of " Infection, degrees B and C,"
were examined under the microscope, and the number of bacilli in the
same was found to be too small for their detection, even when the
cover glasses were prepared from the sediment in the bottoms of
tubes. The latter were of 15 c. c. capacity and had been rotated in a
centrifugal machine for half an hour at the rate of 2,000 revolutions
per minute.
RESULTS OF FEEDIXGS AND INJECTIONS.
The results obtained from the feedings and injections are shown in
the accompanying tables.
RESULTS OF FEEDING AND INJECTING GUINEA PIGS.
TABLE I. Results of injections and feedings of milk " Inft
suspension in water of tubercle bacilli per e<
Action, degree A'' (/ loop of cloudy
suspension in water of tubercle bacilli per each 1O c. c. of milk).
No. of
guinea
pig-
t ,
Date of feed-
ir "g or in J c -
tion.
Total
amount
received.
Date of death.
Autopsy.
6053
Injected
July 13,
1905
5
Died Aug.
1
1905 . . .
Generalized tuberculosis.
0054
...do
do..
a
Died Aug. 5,
190.5 . . .
Do
0079
...do
Julv 21,
1905
;>
Died Aug.
in
l.-tOo. .
DC.
0080
...do
do..
o
Died Aug.
15
1905 . .
Do.
0101
...do
Julv 29,
1905 |
5
Died Sept.
5,
1905...
Do.
0102
...do
do..
5
Died Sept.
s,
1905...
Do.
6119
...do
Aug. 9,
1905
5
Died Aug.
31
1905. .
Do.
0120
...do
do..
Died Sept.
8,
1905...
Do.
6025
Fed
July 13,
1905 i
.50
Killed Oct
2
. 1905..
No lesions of disease.
0020
...do
do..
.50
do
Do.
0027
...do
do..
50
....do....
Generalized tuberculosis.
0028
...do....
do..
50
do....
No lesions of disease.
6029
...do
....do..
50
do....
Do.
6030
...do....
do..
50
do
Do.
6133
...do
Aug. 11.
1905
.50
Killed Oct
2,
), 1905..
Do.
6134
...do....
...do..
.50
do
Extensive tuberculosis.
6135
...do....
do..
.50
do
No lesions of disense.
6130
...lo....
do..
,50
do
Do.
6137
...do
....do..
.50
...do...
Extensive tulxrculosis.
6138
...do
do..
,50
do
Do.
6013
...do
Julv 13
to
1,800
Died Sept.
13
1905..
Generalized tuberculosis.
Aug. 12
1905 :
6014 !
...do...
do..
1.800
Killed Oct
1<
), 1905..
Extensive tuberculosis.
6015"
...do
do..
1,800
do
Do.
6016
...do
do..
1,800
do
Do.
6017
...do
do..
1,800
do
Do.
6018
...do....
do..
1,800
do
Do.
Guinea pigs Nos. 0015 and 0030 each produced two young during the experiment, which on autopsy
were found to be free from disease.
TABLE II. Results of injections and feedings of milk " Infection, degree B'' (1 loop of cloud;/
suspension in water of tubercle bacilli to 10 c. c. of sterile water and 1 loop of the latter per each
We. c. of milk).
Date of in-
jection or
feeding.
Total
amount
received.
Date of death.
Autopsy.
0051
0052
6077
0078
6099
0100
0117
0118
0031
0032
0033
0034
6035
6030
6127
0128
0129
0130
6131"
6132
0043
6044
0045
0040
6047
6048
Inj cted.
Julv 13. 1905
"do
c. c.
5
5
5
5
5
5
5
5
,50
50
50
50
.50
Died Sept.
Killed Oct
Died Sept
Killed Oct
do
27, 1905..
. 21. 1..05..
7. 190.5...
. 21, 1905..
Gener;
D(
D<
I)(
I).
D<
1)(
DC
No les
Pneun
No les
I)(
Inflan
No les
Do
Do
Do
Do
Do
Do
Do
Do
Do
Do
Do
Do
...d<...
do
Julv 21. 1905
"do
...do
do ...
Julv 29, 1905
"do
do
...do
do
Aug. 9, 1905
do
.. .do.
do
Fed
do . . .
July 13, 1905
do
Killed Oct
Died Julv
Killed Oct
do
. 20, 1905..
15. 1905 . .
. 20, 190.5.
do ...
do
do
lo
do
lo
14 190.5
do
do
50
.50
,50
,50
50
50
.50
Killed Oct
Killed Oct
do
. 20, 190.5..
. 2.5, 1905..
...do....
do
Aug. 11, 190.5
lo
do
lo
do
do
lo
do
do . .
lo
do
do
do
do
do
July 13 to
Aug. 12,1905
do
1,800
1 800
Killed Oct
do
. 20, 1905. .
do
do . .
.do
1,800 do
.do
. .do
1,800 .. .do
do
do
1.800
do
.do
.do .
1.800
. .do. .
ii/ed tuberculosis.
One young produced in pen, which on autopsy showed no lesions of disease.
EXPERIMENTS WITH INFECTED MILK.
TABLE III. Results of injections andfeedings of milk" Infection, degree C" (1 loop of cloudy
suspension in miter of tubercle bacilli to 100 c. c. of sterile water and 1 loop of the latter per
each 10 c. c. of milk.)
No. of Tn1(>ctod ' Da to of m-
guinoa Yjffed joctionor
pig. feeding.
Total
amount
received.
Date of death.
Autopsy.
6049 Injected. July 13, 1905
(i050 lo .do . .
c . c.
5
5
5
5
5
5
5
50
50
Killed Oct 21, 1905..
Died Oct. 5, 1905....
Died Oct. 2, 1905....
Killed Oct. 21, 1905..
.. .do
Extensive tiilx'rculosis.
Generalized tuberculosis.
Do.
Extensive tuberculosis.
Do.
Do.
Slight tuberculosis."
Extensive tuberculosis.
No lesions of disease.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
6075
o July 21, 1905
607(1
o do
(i097 ...
ti098
July 29. 1905
.do
do
6115 ...
611(1 . .
Aug. 9, 1905
do
.do.
do
6019 F(
6020
Inly 13, 1905
.'do
do
... . lo
60 4 '1
do
50
50
5(3
50
50
50
50
50
lo
6022
do
. lo
(>02:{
do
do
(1024
do
do
6121 ...
6122
Aug. 11, 1905
do
Kill'd Oct. 25, 1905..
lo
6123 1
o do
. lo
6124 ..
o do
... . lo
6125
50
50
lo
612(1
o . do
do
6037
o July 13 to
1,800
1,800
Killed Oct. 19,1905..
.do...
6038
Aug. 12.1905
o do .
6039
o do
1,800
do
60406
o do
1,800
1.800
do . .
6041
o . .do .
do
6042 do do 1 800
do
i
Tuberculosis limited to one gland near stomach.
b Two young produced in pen, which on autopsy showed no lesions of disease.
An examination of the tables shows that all the guinea pigs injected
with the infected milk contracted tuberculosis, and hence that every
5 c. c. of the milk at all degrees of infectiousness actually contained live,
virulent tubercle bacilli.
Of the guinea pigs that were fed the milk which contained the larg-
est amount of infectious material, 100 per cent of those fed thirty
days and 33J per cent of those fed one day became affected with tuber-
culosis, showing conclusively that the particular tubercle culture used
to infect the milk possessed a sufficient degree of pathogenic virulence
to cause tuberculosis in guinea pigs through ingest ion.
THE SUSCEPTIBILITY OF GUINEA PIGS TO TUBERCULOSIS.
Milk of degrees of infectiousness B and failed to produce tubercu-
losis in a single guinea pig fed with it ; the 12 that were fed thirty days
and consumed each a total of 1,800 c. c. escaped, as well as those fed
only a single day with 50 c. c. each. The amount of infectious material
in the milk was of course very much less than in milk A, but it was
also probably very much greater than the amount present in naturally
infected milk from tuberculous cows whose udders are not affected.
In our experience with milk from tuberculous cows we have never
found a cow with a healthy udder, no matter how extensively she was
otherwise affected with tuberculosis, whose milk, on intraabdominal
injection of guinea pigs, produced tuberculosis with the regularity
DISTRIBUTION OF LESIONS IN GUINEA PIGS. 9
and certainty of our artificially infected milk. From this we may
conclude that the milk feeding practiced in this experiment consti-
tutes quite a severe test of the danger encountered by guinea pigs
through the ingestion of milk from tuberculous cows whose udders are
unaffected. Hence it follows that the ingestion by guinea pigs of
milk from tuberculous cows is a very unsatisfactory test for the pres-
ence of tubercle bacilli. This is surprising to us, because of the com-
monly existing belief that guinea pigs are extremely susceptible to
tuberculosis, irrespective of the manner in which they are exposed to
the infection.
Unfortunately no conclusion can be drawn from the results obtained
with the fed guinea pigs of the danger encountered by man through
the use of milk from tuberculous cattle, and the failure of the guinea
pigs to contract tuberculosis after swallowing innumerable tubercle
bacilli suspended in milk should not be construed as an encouragement
to use the milk of a cow which is known or even suspected to be
affected with tuberculosis. Intestinal tuberculosis of guinea pigs is a
very rare occurrence, even when they are affected with otherwise
generalized tuberculous disease and every other organ is practically
saturated with tuberculous material. It may be that some pecul-
iarity exists about the stomach and intestine of a guinea pig that
allows the bacilli of tuberculosis to pass through and out of the body
more freely than through the intestines of other species of animals,
including man. This view is strengthened by results recently obtained
in some hog-feeding experiments at this station in cooperation with
the Pathological Division, which will be reported in due time. At
this time it is sufficient to say that the hogs in question, on exposure
similar to and no more severe than that received by. the guinea pigs,
readily became affected with tuberculosis.
DISTRIBUTION OF LESIONS IN THE GUINEA PIGS.
The location of the lesions found on post-mortem examination of
the 10 guinea pigs that contracted tuberculosis through the ingestiou
of infected milk warrants a few general remarks. A complete autopsy
record of each guinea pig is not required. The following table shows
the distribution of the lesions in each animal. Taking the number
9 to represent the total amount of disease found in each guinea pig,
the numerals in the table represent approximately the amount of dis-
ease found in the several organs. The highest numeral in connection
with any guinea pig not only indicates that the organ under which it
is placed showed the most extensive tuberculous changes, but that it
was, so far as this could be determined, the first organ to become
affected. Aside from the amount of disease in any one organ as com-
pared M ith any or all the other organs in the same animal, the numerals
31021 No. 86 OG 2
10 EXPERIMENTS WITH INFECTED MILK.
are not intended to convey any impression as to the actual magnitude
of the lesions.
TABLE IV. Distribution of the lesions in 10 guinea pigs affected with tuberculosis through the
ingestion of infected milk.
No. of Throat . Portal Meson-
Lo * # "- *- *.
C.013 1 1 Ijlilll 1 1
(1014 5 1 110 J i
0015 2 2 ill 1 1
0010 422 i
0017 i H H i H 1.J i 2 [ i
0018 3 1 2 ' 2 i
0027 5 1111 10
6134 1 5 i < 1 J 1 i 1 I 1
0037 4 3 J I i ! $ J i
6138 3 2 1 11 1
The remarkable fact about the distribution of the lesions in the
guinea pigs is that, notwithstanding the entrance of the infection w ith
the food, careful search failed to discover lesions of the intestine
except in one case, in which practically every organ was affected.
The mesenteric lymph glands were affected in only 5 of the 10 guinea
pigs, and in no case w r ere the lesions of these glands as important as
those found in other portions of the body of the same animal. The
subcutaneous glands, under which name the glands in the inguinal and
axillary regions are included, were affected in 3 animals; that is, more
frequently than the intestine, as the result of ingested infection,
although these glands are in no direct manner associated with the
organs of digestion.
The liver was affected in 9 animals, but in no case seriously. The
portal glands, thoracic glands, lung, and spleen w r ere affected in
every guinea pig; and the throat glands, although entirely free from
determinable disease in 2 cases, were affected in 8 cases, and 4 of them
show r ed the most marked lesions, being probably the first organs
attacked. The animals which did not show the most extensive
lesions in the throat glands invariably showed the greatest amount of
disease in the thoracic glands.
These facts are interesting mainly because the infection of the
animals was strictly through the food that was eaten by them. While
the infected food had to pass through the mouth and throat to reach
the stomach, its contact w 7 ith these parts was comparatively of short
duration, and its contact w r ith the stomach and bowels of compara-
tively long duration; therefore more extensive disease of the latter and
the associated lymph glands was to be expected.
A SUBCUTANEOUS-INOCULATION EXPERIMENT WITH HOGS.
With reference to the distribution of lesions, the subcutaneous
inoculation of 12 hogs with tubercle bacilli is quite interesting. For
these inoculations tubercle cultures from four different sources were
INOCULATION OF HOC4S. 11
used. All the inoculations were made in the central portion of the
abdominal region, immediately under the skin, just in front of the
navel. The hogs used were part of a number that had been previously
used in hog-disease investigations, and were for that reason unsalable
and unserviceable for most other purposes, but there was nothing in
their condition to unfit them for this experiment.
The tubercle cultures used were obtained from the Pathological
Division of this Bureau and were as follows: (I) A culture isolated
from a human lung, third generation; (2) a culture isolated from the
lung of a boy, a supposedly bovine-human culture, fifteenth gen-
eration; (3) a culture isolated from the lung of a hog that had been
infected with bovine tuberculosis, twenty-second generation, and (4) a
culture isolated from a deer, third generation. For convenience the
cultures will be referred to as Xos. 1,2,3, and 4.
The post-mortem examinations of the hogs were made with the most
scrupulous and searching care, and it is doubtful if any lesions, unless
they were extremely small and well concealed, escaped detection.
The autopsy records give all the lesions found Tbe presence of
tubercle bacilli in every lesion about the nature of which any doubt
existed was microscopically demonstrated.
The records of the hogs follow:
HOGS INOCULATED WITH CULTURE NO. 1.
Hogs Xos. 1751, 1790, and 1805 were each inoculated February 13,
1006. with a small amount of the growth from an agar culture of
tubercle bacillus No. 1, and were killed thirty-seven days later and
examined post-mortem.
Autopsy of hog No. 1751: Weight at time of death, 59 pounds. At the seat of inocula-
tion is an abscess of about 5 nun. diameter, which contains a dry, firm, cheesy material.
The subcutaneous tissues surrounding the abscess in a band less than 3 mm. wide are
sprinkled with minute necrotic foci. Lung contains a few small pearl-like tubercles, 2 mm.
and less in diameter, uniformly distributed.
Autopsy of hog No. 1790: Weight at time of death, from 55 to (iO pounds. At the seat
of the inoculation is an abscess about 1 cm. in diameter, the wall of which is a heavy, dense
neoplastic tissue, inclosing a mass of dry, firm, cheesy material. Lung contains about a
score of minute pearl-like tubercles, the largest of which is not more than 2 mm. in diameter.
Liver contains one small tubercle not more than 1 mm. in diameter.
Autopsy of hog No. 1805: Weight at time of death, (52 pounds. At the seat of the inocu-
lation is an abscess in all respects similar to that found in the same region in hog No. 1751.
Lung evenly sprinkled with innumerable pearl-like tubercles, which vary in si/.e from mere
points to 2 mm. in diameter. Liver contains a few tuberculous foci, 2 mm. and less in
diameter.
HOGS INOCULATED WITH CULTUHK NO. 2.
ITogs Xos. 1754, 1755, and 1708 were each inoculated February 13,
1006, with a small amount of growth from an agar culture of tubercle
bacillus Xo. 2, and were killed thirty-seven days later and examined
post-mortem.
12 EXPERIMENTS WITH INFECTED MILK.
Autopsy of hog Xo. 1754. Weight at time of death, from 55 to 60 pounds. At the seat of
the inoculation is an ahscess about 1 cm. in diameter, which contains a dry, firm, cheesy
material. The subcutaneous tissues surrounding the abscess in a band not more than 5 mm.
wide are sprinkled with minute necrotic foci. Lung evenly sprinkled with innumerable
pearl-like tubercles, the largest of which are 2 mm. in diameter. Liver contains a few
tubercles 1 mm. and less in diameter. Spleen contains a very small number of tubercles
from 1 to 2 mm. in diameter.
Autopsy of hog Xo. 1755. Weight at time of death, 45 pounds. Lesions at the seat of the
inoculation similar to that found in hog Xo. 1754. Inguinal lymph glands slightly enlarged
and contain several necrotic tuberculous areas from 2 to 3 mm. in diameter. Prescapular
lymph glands slightly enlarged and contain several necrotic tuberculous areas from 2 to 3
mm. in diameter, the number of affected areas slightly greater than in the inguinal glands.
Lung evenly sprinkled with innumerable minute pearl-like tubercles, the largest of which
are 2 mm. in diameter. Bronchial lymph glands enlarged and contain a small number of
tuberculous areas. Liver evenly sprinkled with innumerable very minute tubercles.
Portal lymph glands contain a small number of minute tubercles. Spleen contains several
tubercles from 1 to 3 mm. in diameter.
Autopsy of hog Xo. 1798. Weight at time of death, 62 pounds. Lesion at the seat of the
inoculation similar to that found in hog Xo. 1754. Lung uniformly sprinkled with numerous
pearl-like tuberculous nodules from 1 to 2 mm. in diameter. Liver contains a few minute
tubercles.
HOGS INOCULATED WITH CULTURE NO. 3.
Hogs Nos. 1783, 1803, and 1811 were each inoculated February 13,
1900, with a small amount of growth from an agar culture of tubercle
bacillus No. 3, and were killed thirty-eight days later and examined
post-mortem.
Autopsy of hog Xo. 1783. Weight at time of death, 55 pounds. At the seat of the inocu-
lation is an abscess about 1 cm. in diameter, which contains a dry, firm, cheesy material.
The subcutaneous tissues surrounding the abscess in a band not more than 5 mm. wide are
sprinkled with 7iiinute necrotic foci. Lung evenly sprinkled with innumerable minute,
pearl-like tubercles 2 mm. and less in diameter. Liver contains a considerable number of
very minute tubercles. Portal lymph glands contain a few very minute tuberculous foci.
Autopsy of hog Xo. 1803. Weight at time of death, 52 pounds. At the seat of the inocu-
lation is a lesion similar to that found in hog Xo. 1783, but not more than one-half as large.
Inguinal lymph glands enlarged and some of them contain a small number of necrotic areas
4 mm. and less in diameter. Lung evenly sprinkled with innumerable tuberculous nodules
from 1 to 4 mm. in diameter. Bronchial lymph glands enlarged and thicklv sprinkled with
minute necrotic foci. Liver evenly sprinkled with numerous tubercles, the largest of which
are 3 mm. in diameter. Portal lymph glands enlarged and sprinkledjvith many necrotic foci
from 1 to 2 mm. in diameter. Spleen contains a few tuberculous foci from 1 to 5 mm. in
diameter. Lymph glands at the curvature of stomach enlarged and sprinkled with necrotic
foci from 1 to 2 mm. in diameter.
Autopsy of hog Xo. 181 1. Weight at time of death, 55 pounds. At the seat of the inocu-
lation is a lesion similar in all respects to that found in hog No. 1783. One of the inguinal
lymph glands contains a few minute tuberculous foci. Lung evenly sprinkled with numerous
pearl-like tubercles 2 mm. and less in diameter. Bronchial lymph glands greatly enlarged
and sprinkled with tuberculous foci, some of which have a diameter of 2 mm. Liver con-
tains many tulx'rcles from 1 to 3 mm. in diameter. Portal lymph glands contain several
minute foci <;f tuberculosis. Spleen contains several tuberculous foci from 1 to 3 mm. in
diameter.
DISTRIBUTION OF LESIONS IN HOGS. 13
HOGS INOCULATED WITH CULTURE NO. 4.
Hogs Xos. 1772, 1801, and 1809 were each inoculated February 13,
1906, with a small amount of growth from an agar culture of tubercle
bacillus Xo. 4, and were killed thirty-eight days later and examined
post-mortem.
Autopsy of hog Xo. 1772. Weight at time of death, 46 pounds. At the seat of the inocu-
lation is an abscess about 5 mm. in diameter, which contains a dry, firm, cheesy material.
The subcutaneous tissues surrounding the abscess in a band less than 3 mm. wide are
sprinkled with minute necrotic foci. Lung contains many pearl-like tubercles 2 mm. and
less in diameter located principally in the apexes of the various lobes. Liver contains a few
small tubercles, the largest of which are 2 mm. in diameter.
Autopsy of hog Xo. 1801. Weight at time of death, 55 to 60 pounds. At the seat of the
inoculation is a lesion similar to that found in hog Xo. 1772, but about twice as large. Lung
evenly sprinkled with numerous tuberculous nodules from 1 to 3 mm. in diameter. Liver
contains a few very small tubercles.
Autopsy of hog Xo. 1809. Weight at time of death, 61 pounds. At the seat of the inocu-
lation is a lesion precisely similar to that found in hog Xo. 1801. Lung evenly sprinkled
with pearl-like tubercles from 1 to 2 mm. in diameter. Liver contains a few minute tubercles.
DISTRIBUTION OF LESIONS IX THE HOGS.
In the following table the distribution of the lesions in each hog is
shown and an attempt is made to represent the proportionate amount
of the disease in the affected organs by numerals. It should be stated
(as was the case with the guinea pigs in Table IV) that the number
placed under each organ is only intended to show the proportion of the
disease in that organ as compared with the other organs of the indi-
vidual hog and has no bearing on the actual total amount of disease
present in the hog.
The distribution of the disease in each hog is estimated on a scale of
10. When the number 9, for example, is placed in the lung column,
0.75 in the liver, and 0.25 in the spleen column, it means that the mag-
nitude of the lesions in the lung is nine times as great as in the liver
and spleen combined that is, 9 parts of a total of 10, and the lesions in
the liver and spleen would be, respectively, 0.75 part and 0.25 part
of 10. The table of course is only approximately correct, because no
effort was made to isolate and weigh and measure the lesions in the
various organs of the hogs.
The last column of the table shows approximately the magnitude of
the total lesions found in each hog as compared with any other hog.
In estimating the numbers given the actual mass of the tuberculous
tissue present in the body was taken into consideration quite inde-
pendent of its location or distribution, excepting thht the lesions
found immediately at the seat of the inocculation were omitted from
the estimate. For example, if the total lesions found in hog Xo. 1751
are 0.1 and the total lesions found in hog Xo. 1755 are 10 (their
respective values in the table) then the actual relation of the volume
14
EXPERIMENTS WITH INFECTED MILK.
of lesions in the one hog to the other is as 0.1 to 10 or 1 to 100. It may
give additional value to the figures to state that the actual volume of
the tuberculous tissue found in hog No. 1751 (0.1) is equal to about
5 cu. mm.
TABLE V. Distribution f lesions in hogs injected with tubercle cultures.
No.
of
hog.
Material
inoculated.
Ingui-
nal
lymph
glands.
f
Pre-
scapu-
la.r
lymph
glands.
Lung.
Bron-
chial
lymph
g'lands.
Liver.
Portal
lymph
glands.
Spleen.
Lymph
glands ! Rela-
at cur- tive
vature amount
of of dis-
stoin- ease.
!!Ch.
1751
1790
1805
1754
1755
1798
1783
1803
1811
1772
1801
1809
f Tubercle bacillus No.
1 (human lung).
[Tubercle bacillus No.
2 (bo vine-human).
1 Tubercle bacillus No.
f 3 (bovine-hog) .
[Tubercle bacillus No.
f 4 (deer>.
10 00
10
9.90
0.10
1.00
...
V
9. 90
.10
5 00
9.00
25 5 00
| 0.25
0.25
5.00
9.90
0.25
3.75
10
0.25
.25
10.00
? 00
I .
9.00
.75
2.25
3.50
.50
.25
.25
.25
5.00
^
I .25
6.00
5.00
9.50,
.25
.50
.25
.50
0.25 10.00
8.00
1.00
(;;
9 75
.2f>
1.00
I
9 50 .TO
1.00
If we now examine the autopsy records of the hogs as they are pre-
sented in the foregoing table, we see that tubercle cultures Xos. 2 and 3
are somewhat more virulent for hogs than cultures Nos. 1 and 4. This
difference in virulence is not associated with a tendency for the
lesions produced by any culture to localize themselves differently from
the lesions produced by any other culture.
SUSCEPTIBILITY OF THE LUNG TO INFECTION OTHER THAN BY
RESPIRATION.
It will be seen by Table V that the lung was in all the hogs the
principal, and very probably the first, organ to become affected, and
this certainly could not have been due to the point at which the
infectious material was inoculated. The point of inoculation was
specially selected to prevent as far as possible the more immediate
exposure of some one organ and was located much closer to the liver
and spleen than to the lung. The lung disease found was strictly
within the lung, some of it under the pulmonary pleura, but not any
of it on the pleura of either the lung or the chest wall, and among the
twelve affected lungs only three showed an affection of the lymph
glands associated with the lung or contained within the thoracic
cavity. This condition is not regarded as showing a special affinity
of tubercle bacilli for the lung. It is probably due to the fact that the
tubercle germs taken up from the subcutaneous tissues successfully
passed through the lymph channels and various lymph glands and
reached the venous circulation and were then filtered out by the lung.
Whether this view is true or not we have in this experiment a demon-
HOW THE LUNG FILTERS THE BLOOD. 15
stration of the fact that the location of the tuberculous disease in the
body is not necessarily a guide as to the point at which the infectious
material entered.
TESTS SHOWING HOW THE LUNG FILTERS THE BLOOD.
The very effective manner in which the lung filters out solid par-
ticles from the blood was shown at the experiment station by the
injection into the veins of several animals of a carefully prepared sus-
pension in water of pure lampblack. While the specific gravity of
lampblack is much greater than that of water, in the ordinary form in
which the dry substance can be purchased it is so charged with air or
other gases that it is impossible to mix it with water. To overcome
this difficulty we heated the lampblack in a crucible to a red heat and
put it into water while hot, and found that fully 75 percent of the mass
sank to the bottom at once.
Two rabbits were placed under the influence of ether and 1 c. c. of a
suspension of about 10 per cent, by weight, of lampblack in water was
injected into their ear veins. The result was almost instantaneous
death. Two more rabbits without being placed under the influence
of ether were injected in the same manner with the same result:
Ether was used in the first instance because it was thought the little
animals would suffer long and severely as a result of the injection. It
was omitted in the second instance because the operation, followed by
almost instantaneous death, caused no more suffering than is endured
by exposure to ether during the time that precedes loss of consciousness.
The autopsies of the four rabbits showed identical lesions a uniform
distribution of the injected lampblack throughout the lungs and no
trace of the intensely black, very fine, and practically impalpable
powder in any other portion of the body.
A horse was also given an intravenous injection of lampblack sus-
pension. In this case the injection was made into the jugular vein
and the amount of material in proportion to the weight of the animal
was much smaller than that injected into the rabbits. The dose was
intentionally made small (50 c. c. of a 1 per cent suspension) so as not
to greatly affect the horse, which was an old, vicious animal, not
serviceable for other experimental purposes and not safe for ordinary
work. The actual amount of lampblack introduced into the circula-
tion of each rabbit was 100 milligrams (1 ,V grains) and into the horse
500 milligrams (7-j y grains). As the horse weighed about five hun-
dred times as much as each rabbit the dose it received per weight of
animal was one one-hundredth of that received by the rabbits.
The only ante-mortem effect of the injection into the horse was an
increased rapidity of the respiration, which lasted several hours and
then subsided. About a week after the injection the horse was killed
and examined post-mortem. The autopsy revealed the presence of an
16 EXPERIMENTS WITH INFECTED MILK.
even distribution of the lampblack in the lung and no trace of the sub-
stance in any other portion of the body. The particles of lampblack
in some portions of the lung were very fine and could not be seen with-
out magnification.
Similar evidence of the property of the lung to filter the blood has
been observed in the various intravenous injections of tubercle
bacilli into cattle that have been made from time to time at the Experi-
ment Station. Dead tubercle germs or tubercle germs of a virulence
too low to cause a progressive tuberculous disease when injected into
the veins of cattle invariably lodge in the lung and nowhere else
where it has been possible to discover them, and cause a miliary tuber-
culosis from which, if the germs are either dead or very attenuated,
recoverv is slowly made.
SPREAD OF INFECTION TO OTHER ORGANS.
Next to the lung the organ most frequently affected is the liver,
which was affected in 11 cases out of 12, and in 6 of these cases it
is the only organ in addition to the lung in which the affection had
made its appearance. Following its appearance in the liver we find
the disease spreading with equal rapidity to the spleen, portal lymph
glands, and bronchial lymph glands, and from then on a tendency to
rapid generalization is shown.
If the disease in the liver followed that in the lung, which is almost
certain in the twelve injections with which we are dealing, it is more
likely to have received the infectious material from the lung than
from the seat of the inoculation. Infectious material from the lung
we believed entered the circulation through the pulmonary veins and
was carried in the blood to the heart and thrown into the arterial cir-
culation and filtered out when the blood reached the liver, the pecu-
liar circulation of which may specially enable it to act as a very
efficient natural filtering system.
REMARKS ON THE IIO<! INOCULATIONS.
There are some facts that must be kept in mind in estimating the
practical significance of the course followed by the tuberculous disease
in this group of hogs. First, the affection was produced by the intro-
duction of a number of bacilli vastly greater than is likely to occur with
a natural exposure; hence the number of individual original foci of
disease that developed simultaneously was vastly greater than from a
natural infection. Second, there is a condition known as immunity
to tuberculosis that can be produced by either the intravenous or the
subcutaneous injection of tubercle bacilli of a. pathogenic virulence
somewhat less than is required to cause an active, progressive tuber-
culosis.
The first fact probably caused the presence of many more germs in
the blood of the hogs at all times after the inoculation than occurs in
NEW SIGNIFICANCE OF LUNG INFECTION. 1 7
the case of a naturally acquired tuberculosis, and a deposition of these
germs first of all in the lung, then in the liver, then in the spleen, and
later in other structures, from which they were taken up by the lymph
glands.
In a naturally acquired tuberculosis, that begins with possibly one
or two or at most a few foci of disease in one organ, the other organs
of the body have time to acquire some immunity similar to that
referred to as the second fact. Such immunity would play a very
small part in protecting the organs of the inoculated pigs, because of
the intense character of the exposure and the rapid spread of the
disease. We have in the hogs a strictly acute tuberculosis, and wish
to distinguish this from the chronic form in which the affection is
usually encountered in nature among men and other animals. This
probably explains the absence of lymph-gland disease in 8 of the 12
hogs. In the acute disease we have the distribution of infectious
material going on through the circulation: in the chronic disease we
have the increase progressing about the peripheral portions of each
focus and, because of their incessant exposure, an early affection of
the lymph glands that first receive the drain from the tissues in which
the lesions are located; and when in the chronic disease an occasional
bacillus is carried by the blood to the liver or spleen the acquired
resistance the immunity that may be caused in some organs by the
presence of tuberculosis in other organs prevents the development
of fresh disease in most instances. This view receives some support
from the fact that animals, for example, with extensively tuberculous
lungs swallow an amount of infectious material many times greater
than healthy animals can obtain anywhere on natural exposure
without necessarily causing tuberculous disease of the throat glands
or abdominal organs. The ingestion of infectious material is evi-
dently much more dangerous to healthy animals than to the still
unaffected organs of animals already affected with tuberculosis, and
if the records of the guinea pigs in the first portion of this article have
any value they show that ingested tuberculous material is more apt
to cause disease of the throat and lungs than of any structure con-
tained in the abdominal cavitv.
NEW SIGNIFICANCE OF LfXC INFECTION.
The supposition that tuberculosis of the lung is commonly due to
respired infection is shown to be unnecessary to account for the pres-
ence of the disease more frequently in the lung than in other portions
of the body. The lung, it seems, is most commonly affected simply
because the lymph collected from all portions of the body, after it
reaches the blood circulation, must pass through the lung before it
reaches any other organ, and the lung evidently will not admit of the
passage of solid particles, other than the elastic blood corpuscles,
18 EXPERIMENTS WITH INFECTED MILK.
through its filtering net of capillaries. The result is that it makes no
difference at what point the tuberculous material enters the body
there is nothing to protect the lung from infection but the lymph
glands, and that the lymph glands frequently allow tuberculous
material to pass through them or by them without becoming affected
is conclusively shown by the series of hog inoculations.
The inoculations of the hogs were superficial in the middle of the
abdominal region and the lung was affected in 100 percent of cases,
and in only 25 per cent of cases was any disease present in the lymph
glands in any portion of the thoracic cavity. In 58J per cent of cases
the disease was confined entirely to the lung and liver, without disease
of any lymph gland in the body.
Of course there may be some difference between the anatomical
structure of the lymph glands of hogs and other animals of a kind
that will allow the easier passage of bacteria through the former,
and likewise similar differences in the structure of the lymph glands
located in different portions of the body of the same animal. But
that does not greatly militate against the conclusion that the lung
is more directly exposed to tuberculous affection, respired affection
left out of consideration, than any other organ.
Respired infectious material comes to rest in the lung on the
mucous surface of the bronchial tubes and is then still located on
what may be regarded as one of the exterior surfaces of the body. In
this location, because of the irritation produced by the material with
which it gains entrance dust, etc. it has an excellent chance to
become enveloped with mucous secretions and to be coughed up and
either swallowed or expectorated. This consideration, taken in con-
nection with the facts we have presented to account for the more
frequent presence of the disease in the lung than elsewhere, seems to
show that tuberculosis due to bacilli that enter the lung with the
breathed air is an uncommon affection. If this conclusion is true,
its practical significance lies in the caution to be doubly sure that our
food and drink is free from tubercle germs, and especially that it is
wise to avoid the use of the milk produced by tuberculous cows or in
stables containing tuberculous cattle.
RESISTANCE OF TUBERCLE GERMS.
The tubercle bacillus is a peculiar organism in its conduct in the
animal body, independent of its real pathogenic significance. When
cultures of other bacteria are injected into the body of an animal
insusceptible to the affection of which the germs in question may be
the specific cause, these germs or bacteria disappear entirely from
the body in a very short time. The same is not true of the bacillus
of tuberculosis; on the contrary, it shows an enormous resistance
to the destroying and annihilating processes that are brought to bear
SUMMARY. 19
against it by the body. Even dead or sterile cultures of tubercle
bacilli injected into cattle or sheep remain lodged in the tissue for
months and years in a manner in which their presence can be micro-
scopically demonstrated.
SUMMARY.
To sum up, we believe the experiments presented have shown the
following facts:
1. That the high susceptibility of guinea pigs to tuberculosis holds
good only when the infectious material is introduced into the body
in a way in which it can not escape through the natural excretory
organs; that is, when it is injected under the skin, into the abdominal
cavity, into the veins, into the thorax, ptc.
To strengthen this conclusion, we may add that we recently exposed
52 guinea pigs and 6 hogs to tuberculosis through milk feeding, the
milk given the guinea pigs and the hogs being indentical in its infec-
tious character. The result was that 5 of the 6 hogs contracted
tuberculosis and the 52 guinea pigs remained unaffected and in
perfect health. A more detailed report of this experiment will be
published at another time.
2. That the localization of tuberculous disease in the lung of an
animal gives us no information as to the point at which the infectious
material entered.
3. That the lung is more especially and directly exposed to tuber-
culous affection than any other organ, because of the character of its
circulation and because the entire lymph stream that is poured into
the circulation must pass through the lung before it reaches the capil-
lary structures or smaller and finer vessels of any other organ.
4. That it is not necessary to account for the great frequency
with which tuberculosis localizes itself in the lung by supposing that
the most common form of exposure to tuberculosis is through the
respiration.
5. That the experiments, taken as a whole, direct special attention
to the danger sustained through exposure to tuberculous material
that enters the body with the food. This fact can not be too
strongly emphasized.
o
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