TUBERCULOSIS. 257 



stance contained within the bodies of the bacilli can be 

 extracted only with great difficulty. 



If dead tubercle-bacilli are inoculated into rabbits by in- 

 travenous injection, and the animals are subsequently killed 

 (some of them die spontaneously), the lungs and the liver are 

 found strewn with small nodules, consisting of round cells 

 and epithelioid cells, giant-cells, which contain dead tubercle- 

 bacilli, and which are thus indistinguishable from true 

 tubercles. Prudden and Hodenpyl, who were the first to 

 make these observations, believed the formation of the 

 tubercle to be a result of the activity of a specific bacterial 

 proteid contained within the protoplasmic body of the tuber- 

 cle-bacilli. Baumgarten does not agree with this opinion, 

 considering the formation of nodules by the dead bacteria 

 as tuberculosis due to a foreign body (p. 276). The agency 

 through which tubercle-bacilli in general give rise to the 

 formation of tubercles, and whether a toxic influence is 

 operative, are questions that also have not yet been deter- 

 mined with certainty with regard to the living bacilli. It 

 is undoubted, however, that the tubercle is a direct result 

 of the presence of the tubercle-bacillus, for this is found 

 in every tubercle, and wherever it is introduced into animals, 

 there tubercles develop with certainty. It is noteworthy 

 that in the clinical picture of tuberculosis manifestations 

 of general intoxication are not conspicuous so long as the 

 process is in its incipiency, is localized, and mixed infec- 

 tion has not yet taken place. 



Pathologic Anatomy of Tuberculosis in Animals. 

 In different varieties of animals the bacilli cause anatomic 

 changes of a widely different character. Thus, in the liver 

 and the spleen of guinea-pigs coagulation-necrosis occurs, 

 without true caseation ; in monkeys rapid softening takes 

 place, with the formation of a thin, diffluent purulent secre- 

 tion ; in the tuberculosis of cows there is simultaneous cal- 

 cification and caseation. The most common product of 

 tubercle-bacilli in animals is, however, the tubercle, which 

 is also always encountered in connection with the experi- 

 mental development of tuberculosis, and which resembles 

 in every respect the tuberculous nodule of human tuber- 

 culosis to be described shortly. 



Portals of Entry for the Tubercle-bacillus in Human 

 Beings. The tubercle-bacillus most frequently gains en- 

 trance into the human body through the respiration by way 

 17 



