270 CLINICAL BACTERIOLOGY. 



ever, have thus far proved unsuccessful. Richet maintained 

 for a time that he had succeeded in vaccinating dogs by 

 inoculating them with the bacilli of fowl-tuberculosis, or 

 with small amounts of mammalian tubercle-bacilli, but his 

 observations have not been confirmed. 



R. Koch endeavored to secure a direct and specific in- 

 fluence upon the tuberculous lesions by means of tuberculin. 

 This product was obtained by concentrating mature 

 bouillon-cultures of tubercle-bacilli (from six to eight 

 weeks old) to one-tenth of their volume over the water- 

 bath, and freeing the culture-fluid of the bodies of the 

 dead bacilli by means of filtration through porcelain or 

 gravel. Experimental observation showed that healthy 

 guinea-pigs withstand without harm subcutaneous injec- 

 tions of as much as two cubic centimeters of tuberculin, 

 whereas tuberculous animals, infected four weeks previ- 

 ously, succumb to a dose of 0.6 cu. cm. On autopsy 

 in cases of animals dead after injections of tuberculin the 

 following conditions were found : The site of tuberculous 

 inoculation was markedly reddened, as well as the adjacent 

 lymph-glands. In the viscera enormous dilatation of the 

 capillaries surrounding the tuberculous foci was discernible 

 microscopically. The hemorrhage-like spots on the sur- 

 face of the liver were quite pathognomonic. In tuber- 

 culous guinea-pigs treated with small doses of tuberculin 

 (at first I mg., increasing to o. I and 0.2 gram) a striking 

 effect upon the morbid condition was observed. Improve- 

 ment in the primary area of inoculation in the abdominal 

 wall was observed, with diminution in size of the adjacent 

 tumid lymph-glands, but complete recovery, as later reports 

 from the Koch Institute have shown, occurred only excep- 

 tionally. The animals survived for a longer time than 

 tuberculous control guinea-pigs not treated with tuberculin. 

 Postmortem examination in the case of animals treated 

 disclosed marked retrogression, in part cicatrization of the 

 tuberculous lesions in the abdominal viscera, but eventually 

 death resulted from pulmonary tuberculosis. 



The curative influence of tuberculin is explained by Koch 

 on the assumption that as a result of its action the necrotic 

 substance, which is always present in the neighborhood of 

 a tuberculous lesion, is increased in amount, so that coag- 

 ulation-necrosis occurs throughout a wide extent, and 

 this hinders the bacillus in its further growth, and at 



