580 INFECTION AND IMMUNITY. 



glycerin and water, Neutuberculin Koch (BaziUen- 

 emulsion). 



other Preparations which in many respects are analo- 

 gous to those of Koch have been made by various 

 investigators; the tuberculocidin of Klebs, the tu- 

 berculins of de Schweinitz and Dorset and that of 

 Denys, . the two tubercule toxins of Maragliano. 

 which he utilizes for the preparation of antitoxic 

 serums, the oxy tuberculin of Herschf elder, the 

 "TD" and the "TDK" of Behring and the tubercu- 

 loplasmin of Buchner. Marmorek claims to have 

 obtained the true toxin of the tubercle bacillus by 

 growing young, vigorous cultures on a complicated 

 medium, denying that tuberculin represents the 

 true toxin of the organism. 



standard- Tuberculin can not be standardized with accur- 

 ac ^ Because of the extraordinary susceptibility of 

 tuberculous animals to tuberculin, Koch decided to 

 estimate its value by the quantity required to kill 

 such animals. From 0.5 to 1 c.c. of tuberculin, 

 when injected into a healthy guinea-pig, causes 

 neither a local nor a general reaction, whereas 

 from 0.1 to 0.15 c.c. kills a tuberculous guinea- 

 pig in from 24 to 48 hours. For stand- 

 ardization von Lingelsheim recommends intracere- 

 bral injection into healthy guinea-pigs, because 

 of the extreme toxicity of tuberculin when 

 introduced into the central nervous system; only 

 1/180 as much tuberculin was required to cause 

 death by intracerebral injections as compared with 

 subcutaneous or intraperitoneal. Behring bases the 

 value of tuberculin on its toxicity for healthy 

 guinea-pigs and in his terms the expression "1 

 c.cm. = 1,000 M." means that one gram of the 

 toxin is fatal to 1,000 grams of guinea-pig tissue. 



