292 THE TUBERCLE BACILLUS 



avian tubercle bacilli are merely two varieties of the same species adapted to different 

 conditions. 



(c) The ichthic tubercle bacillus. The ichthic tubercle bacillus is more 

 sharply differentiated from its congeners (vide infra) but some observers, 

 notably Moeller, Sorgo and Suess [report that they] have succeeded in con- 

 verting an human into an ichthic tubercle bacillus. 



It appears to be true that all tubercle bacilli have a common origin, and that 

 acclimatization under parasitic conditions in different animals has led to the 

 creation of the four different types. 



2. Human tuberculosis. 



Man becomes infected with tuberculosis either by way of the respiratoi 

 or digestive tracts, more rarely by the skin and genital passages. 



The tubercle bacillus is found in all tuberculous lesions in the hums 

 subject. 



[As to the aetiology of human tuberculous phthisis opinion is somewhat 

 sharply divided. The original theory was that tuberculous phthisis is com- 

 monly caused by the inhalation of tubercle bacilli. This doctrine received 

 the support of Koch, Cornet, Pfliigge and others. Chauveau however put 

 forward the view many years ago that phthisis was not uncommonly caused 

 by bacilli which had been ingested and absorbed from the intestine, and in 

 recent years this doctrine has been strongly advocated by Behring.] 



Behring thinks that infection generally takes place through the alimentary 

 canal and that pulmonary tuberculosis of adults is merely a later stage of an 

 intestinal infection contracted in the early years of life. Calmette and 

 Guerin confirm this opinion [in so far as it relates to the channel of infection 

 in phthisis ] ] and bring forward numerous experiments to show that pulmonary 

 tuberculosis (not inoculated) is always a sequela of a primary intestinal 

 infection of which in the adult no trace of the original lesions in the mesenteric 

 glands or abdominal viscera can be detected. [Calmette bases his opinion 

 upon experiments on goats and bovines and on the researches of his pupils, 

 Van Steenberghe and Grysez, on experimental anthracosis. E-avenel also 

 from his own observations is led to believe that infection of the tonsils is the 

 most frequent cause of apical tuberculosis but that infection may take place 

 from any part of the alimentary canal and that the bacilli may pass through 

 the wall of the intestine without leaving any indication of the site of infection 

 in the form of a local lesion. 



[The view that phthisis is commonly caused by the inhalation of tubercle 

 bacilli is, however, supported by many recent investigations. Cobbett, for 

 instance, believes " that phthisis is commonly caused by the inhalation of 

 tubercle bacilli " and from the results of an elaborate series of experiments 

 devised to ascertain the aetiology of pulmonary tuberculosis in which he 

 repeats many of Calmette's experiments this observer concludes that the 

 intestine is not a common portal of entry for the tubercle bacilli which cause 

 phthisis. The experiments of the English Commission again though they 

 demonstrate " that a considerable amount of the tuberculosis of childhood 

 is to be ascribed to infection with bacilli of the bovine type transmitted to 

 children in meals consisting largely of milk of the cow " nevertheless do not 

 entirely support the theory that pulmonary tuberculosis is a sequela of a 

 primary intestinal infection as may be seen from the widely different propor- 



[ l Calmette does not state that the infection in pulmonary tuberculosis is necessarily 

 an infantile infection but merely that at whatever age infection of the lungs occurs the 

 channel of infection is invariably the alimentary canal.] 



