BACILLI IN CHRONIC INFECTIOUS DISEASES. 481 
injections, but die within seventeen to twenty days when virulent— 
recent—cultures are injected into the circulation. As a result of 
such an inoculation the animal rapidly loses flesh and has a decided 
elevation of temperature, commencing at the end of the first week 
and increasing considerably during the last days of life. At the 
autopsy the spleen and liver are found to be greatly enlarged, but 
they do not contain any tubercles that can be recognized by the naked 
eye (Yersin). They contain, however, great numbers of tubercle 
bacilli, both free and in the cells. Injections of a small quantity of 
a pure culture into the anterior chamber of the rabbit’s eye cause 
first iris-tuberculosis, followed by swelling and caseation of the near- 
est lymph glands, and finally general infection and death ; when 
larger quantities are injected general tuberculosis is quickly devel- 
oped. The influence of quantity—number of bacilli—is also shown 
in subcutaneous, intravenous, or intraperitoneal injections into guinea- 
pigs and rabbits (Hirschberger, Gebhardt, Wyssokowitsch). Thus 
rabbits which received less than one hundred and fifty bacilli, in 
sputum, in the experiments of Wyssokowitsch, did not develop tuber- 
culosis ; and in guinea-pigs the smaller the number injected the more 
protracted the course of the disease was found to be. 
Tuberculosis in man no doubt results, in a large proportion of the 
cases, from the respiration, by a susceptible individual, of air con- 
taining the tubercle bacillus in suspension in a desiccated condition. 
As already stated, it has been demonstrated by experiment that the 
bacillus retains its vitality in desiccated sputum for several months. 
The experiments of Cornet have demonstrated that in the dust of 
apartments occupied by tuberculous patients tubercle bacilli are very 
commonly present in sufficient numbers to induce tuberculosis in 
guinea-pigs inoculated in the peritoneal cavity with such dust, while 
negative results were obtained from inoculations with dust from 
other localities. In view of these facts the usual mode of infection 
is apparent. Infection may also occur through an open wound or 
abrasion of the skin, as in the small, circumscribed tumors which 
sometimes develop upon the hands of pathologists as a result of 
handling tuberculous tissues. A few instances of accidental inocu- 
lation through wounds made by glass or earthen vessels containing 
tuberculous sputum have also been recorded. A more common mode 
of infection, especially in children, is probably by way of the intesti- 
nal glands, from the ingestion of the milk of tuberculous cows. That 
infection may occur by way of the intestine has been proved by ex- 
periments upon rabbits, which develop tuberculosis when fed upon 
tuberculous sputum. And that the tubercle bacillus is frequently, if 
not usually, present in the milk of tuberculous cows has been proved 
by the experiments of Bollinger, Hirschberger, Ernst, and others. 
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