BACILLI IN CHRONIC INFECTIOUS DISEASES. 409 



bacillus, into the peritoneal cavity give rise to extensive tuberculo- 

 sis of the liver, spleen, and lungs, and to death, as a rule, within 

 three or four weeks. Rabbits are less susceptible to subcutaneous 

 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 

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