Lesions 731 



The experiments of Koch, Prudden, and Hodenpyl,* and 

 others have shown that when dead tubercle bacilli are in- 

 jected into the subcutaneous tissues of rabbits, small local 

 abscesses develop in the course of a couple of weeks, show- 

 ing that the tubercle bacilli possess chemotactic properties. 

 These chemotactic properties ' seem to depend upon some 

 other irritant than that by which the chief lesions of tuber- 

 culosis are caused. When the dead tubercle bacilli, instead 

 of being injected en masse into the areolar tissue, are intro- 

 duced by intravenous injection and disseminate themselves 

 singly or in small groups, the result is quite different, and 

 the lesions closely resemble those caused by the living or- 

 ganisms. 



Baumgarten, whose researches were made upon the iris, 

 found that the first irritation caused by the bacillus is 

 followed by multiplication of the fixed connective-tissue 

 cells of the part. The cells increase in number by karyo- 

 kinesis, and form a minute cellular collection or primitive 

 tubercle. Such leukocytes as occur are of the small mono- 

 nuclear variety, are of secondary importance, appear later, 

 and are no doubt attracted both by the chemotactic sub- 

 stance shown by Prudden and Hodenpyl to exist in the 

 bodies of the dead bacilli and by the necrotic changes already 

 affecting the tissue in which the tubercle occurs. For rea- 

 sons not understood, the number of lymphocytes varies con- 

 siderably in different cases. Sometimes there will be enough 

 to justify the name " tuberculous abscess "; sometimes they 

 will be completely absent. 



The essential toxic substance of the bacillus does not 

 cause the chemotaxis, for when the lymphocytes are absent 

 the characteristic coagulation-necrosis persists. 



The group of epithelioid cells and lymphocytes constituting 

 the primitive tubercle scarcely reaches visible proportions 

 before coagulation-necrosis begins. The cytoplasm of the 

 cells takes on a hyaline character, and appears to become 

 abnormally viscid, contiguous cells tending to fuse. The 

 chromatin of the nuclei becomes dissolved in the nuclear 

 juice and gives a pale but homogeneous appearance to the 

 stained nuclei. Sometimes this nuclear change is only 

 observed very late. There is little karyorrhexis. As the 

 necrosis advances, some of the cells flow together and form 

 large protoplasmic masses giant-cells which contain as 

 * "New York Med. Jour.j" June 6-20, 1891. 



