230 TUBERCULOSIS. 



duced as a curative agent for tubercular affections. He 

 had observed that if in a guinea-pig suffering from the initial 

 local induration occurring after subcutaneous inoculation 

 with tubercle bacilli, a second subcutaneous inoculation of 

 tubercle bacilli, or of dead cultures of the same, was 

 practised in another part of the body, superficial ulceration 

 occurred in the primary tubercular nodule, the wound 

 healed, and the animal did not succumb to tuberculosis. 

 There thus appeared to exist in tubercle cultures a sub- 

 stance having a healing action in tuberculosis, and an 

 extract containing this substance Koch named tuberculin. 

 A veal bouillon containing i per cent peptone, and 4 to 5 

 per cent glycerine, was inoculated with tubercle bacilli and 

 incubated for from six to eight weeks at 38 C. It was evapor- 

 ated to ^th of its bulk, and the bacilli were killed by an 

 hour's exposure at 100 C. The result was the tuberculin, 

 and it would evidently contain dead, and often macerated, 

 bacilli, and whatever substances these bacilli contained, 

 non-volatile products formed by them from the food material 

 when alive, and the concentrated remains of the bouillon and 

 glycerine. The bacterial products present, whether origin- 

 ally extra- or intra- cellular, would only be such as would 

 not be destroyed at 100 C. The injection of .25 c.c. of 

 tuberculin into a healthy man causes, in three to four hours, 

 malaise, tendency to cough, laboured breathing, and moder- 

 ate pyrexia; all of which pass off in twenty-four hours. 

 The injection (the site of the injection being quite un- 

 important), however, of .01 c.c. into a tubercular person 

 gives rise to similar symptoms, but in a much more 

 aggravated form, and in addition there occurs around any 

 tubercular focus great inflammatory reaction, resulting in 

 necrosis and a casting off of the tubercular mass, when this 

 is possible. These appearances could be well seen in such 

 a superficial tuberculosis as lupus. The bacilli were, it was 

 shown, not killed in the process. Koch's theory of the 

 action of the substance was that the tubercle bacillus 

 ordinarily secretes a body having a necrotic action on the 

 tissues. This body is contained in tuberculin, and when the 



