BACTERIUM TUBERCULOSIS 405 



one from the other, that no fixed law as to what will appear 

 at autopsy can a priori be laid down. 



The guinea-pig, which is best suited for this experiment 

 because its susceptibility to tuberculosis is greater and more 

 constant than that of other animals usually found in the 

 laboratory, presents, in the main, changes that are charac- 

 terized by coagulation-necrosis and caseation. This is 

 particularly the case when the infection is general — i. e., 

 when the process is of the acute miliary type; then the tissues 

 of the liver and spleen present the most favorable field for 

 the study of this pathological-anatomical alteration. 



In general, the tubercular lesions can be divided into 

 those of strictly focal character — i. e., the miliary and the 

 conglomerate tubercles — and those which are more diffuse. 

 The latter lesions, although primarily of the same nature 

 as the miliary tubercles, are much greater in extent and not 

 so sharply circumscribed. These latter lesions play a more 

 conspicuous role in the pathology of the disease than do 

 the miliary nodules, although it is the miliary nodules 

 (tubercles) that give to the disease its name. 



At autopsy the pathological manifestations of the disease 

 are not infrequently seen to be confined to the seat of inocu- 

 lation and to the neighboring lymphatic glands. These 

 tissues then present all the characteristics of the tuberculous 

 process in the stage of cheesy degeneration. When the 

 disease is more general the degree of its extension varies. 

 Sometimes the small gray nodules — miliary tubercles — are 

 only to be seen with the naked eye in the tissues of the liver 

 and spleen. Again, they may invade the lung, and frequently 

 they are distributed over the serous membranes of the 

 intestines, the lungs, the heart, and the brain. These gray 

 nodules, as seen by the naked eye, vary in size from that of 



