Tubercle Bacilli in the Feces of Cattle. 8i 
(b) the mixed feces, and (c) watery mucus scraped from the rectum, 
each stained slide being searched fifteen minutes with the aid of a 
mechanical stage. If organisms indistinguishable in appearance 
from bovine tubercle bacilli were found upon any of these slides 
the examination was recorded as positive. One hundred and nine- 
teen samples from 53 cows which had reacted to tuberculin were 
examined in this way, with a positive result 53 times in samples 
from 34 of the cows. Thirty-five other samples from these same 
cows were negative. Nineteen cows gave negative results at all 
examinations, 31 in number. Thus, of the 53 cows tested, 34, or 
64.2 per cent., gave a positive result at one or more tests, and 19, 
or 35.8 per cent., gave only negative results. Forty samples from 
18 non-reacting cows were tested in the same way, with 23 positive 
and 17 negative results. Fifteen of the 18 cows, or 83 per cent., 
gave a positive result at one or more tests, while only 3, or 17 per 
cent., were negative at all tests. From this it appears that no sig- 
nificance in respect to the presence of tubercle bacilli can be at- 
tached to the finding of^ a few acid-fast bacteria in the feces of 
cattle. 
In order to test the delicacy of guinea pig inoculation as a test 
for tubercle bacilli in the feces of cattle, a number of experiments 
were performed in which accurately measured minute quantities 
of a pure culture of bovine tubercle bacilli were added to definite 
amounts of cow feces, previously shown to be free from tubercle 
bacilli. In this way it has been ascertained that as small a quan- 
tity as iXiO" 11 gram of tubercle bacilli, suspended in one cubic 
centimeter of emulsion of feces, produces generalized tuberculosis 
upon subcutaneous injections into guinea pigs. The actual 
number of bacterial cells in this amount of culture would probably 
be between 5 and 500. 
One hundred and four samples of feces from 62 reacting cattle 
have been tested by inoculation of guinea pigs. Virulent tubercle 
bacilli were thus detected in feces from three of these animals, or 
practically 5 per cent. No relation was found between the pres- 
ence of visible acid-fast bacteria in the microscopic test and the 
presence of virulent tubercle bacilli as shown by guinea pig inocu- 
lation. 
Whether the percentage of reacting cattle passing tubercle 
