36o MICRO-ORGANISMS AND DISEASE [chap. 



In August 1890, on the occasion of the International 

 Medical Congress held in Berlin, and in subsequent publi- 

 cations, Koch announced that by experiment on guinea- 

 pigs he had ascertained that when guinea-pigs, previously 

 made tubercular by subcutaneous inoculation, be inoculated 

 again with extracts (glycerine extract) of sterilised tubercle 

 cultures, the growth itself from the surface of serum or 

 glycerine Agar being rubbed down and extracted with 

 dilute glycerine, or with the filtrate of glycerine broth cul- 

 tures (previously sterilised), the tubercular glands undergo a 

 rapid necrosis and elimination, brought about by an acute 

 reactive inflammation setting in in the tissues around the 

 tubercle, but the tubercle bacilli themselves are not affected 

 by it. He then applied this method of injecting glycerine 

 extract of tubercle cultures — tuberculin — in very small doses, 

 o'ooi-o'oi gramme, on the human subject, lupus, bone 

 tuberculosis, early pulmonary tuberculosis. The result was 

 remarkable, since most patients affected with one or another 

 form of tuberculosis reacted very conspicuously to such 

 injection, high temperature, great local congestion and 

 inflammation in lupus and bone tubercle ; persons not 

 affected with tubercle, as a rule, not showing any reaction 

 to such small doses. In lupus, bone and joint tubercle, 

 the tubercular tissue becomes necrotic, is either sponta- 

 neously eliminated, as in lupus, by the reactive inflammation 

 of the surrounding tissue, or can be removed by surgical 

 aid, as in tuberculosis of bone. Tuberculin is, then, a 

 distinct means of diagnosing tubercle, otherwise not easily 

 diagnosed. 



Weyl has analysed the tuberculin, and found that the 

 essential portion of it is a substance related to mucin, not 

 to albumin. 



Good therapeutic results have been obtained with the 



