THE MICROBIAL TOXINS. 69 



the serum of animals that have succumbed to the 

 symptomatic anthrax is capable of vaccinating 

 against this disease; we have here a new proof 

 that the antitoxin is in fact a product of the defense 

 of the cells of the organism, and the author men- 

 tioned has been able to vaccinate guinea-pigs by 

 injecting into the peritoneum culture bouillon 

 sterilized by heating to 115 C. or by filtering 

 through porcelain. 



Tubercular Toxin. The culture bouillons of 

 Koch's bacillus contain one or more active sub- 

 stances which constitute, and which is at the 

 present designated as, tuberculin.* Koch's thera- 

 peutic tuberculin is obtained by evaporating to 

 one-tenth its volume a culture bouillon of Koch's 

 tubercle bacilli prepared from a 4-per cent, gly- 

 cerinic mutton bouillon, and filtering through porce- 

 lain. By fractional precipitation it is possible to 

 obtain from the crude tuberculin so prepared a 

 product which is considered as pure tuberculin, and 

 which possesses considerable activity. 



Prolonged boiling on the water-bath completely 

 destroys the activity of this tuberculin, which 

 moreover hardly ever keeps longer than three 

 weeks. It has been found possible to preserve it 

 for an indefinite period, however, by adding to 



*AUCLAIR: Thhe de doctoral, Paris, 1897; and Arch, de 

 Mdecine, exp. 1898. 



