SECTION VI. 



TESTS WITH PRECIPITIXS. 



I. PHYTOPRECIPITINS. 

 Bacterioprecipitins. 



UNDER the name of Bacterioprecipitins I include the precipitins 

 discovered by Kraus in the serum of animals treated with certain 

 bacteria, which act upon culture-filtrates of the corresponding germs, 

 or upon a solution of the substance of such micro-organisms. It will be 

 remembered that these were the first precipitins to be discovered. 



Kraus (30, iv. 1 and 12, vm. 1897) found that if he added cholera, 

 plague or typhoid antisera to filtrates of the corresponding cultures, 

 that a precipitation took place. The antisera were obtained from 

 animals which had been immunified. The culture-filtrates were prepared 

 by passing the culture-fluid through porcelain filters. A filtrate of 

 crushed germs gave the same result as the filtered culture-fluid, proving 

 that the precipitable substance was present within the bacterial cell. 

 The antisera only acted upon their homologous cultures. Filtrates of 

 B. diphtheriue to which antitoxic horse-serum was added, on the other 

 hand, did not give a precipitum. Kraus allowed the reaction to take 

 place at 37 C., observing the precipitum after 24 hours. He states 

 that the latter appeared to be composed of alkali-albuminate and 

 peptone, and notes that it is necessary to add more antiserum in 

 making these tests than is the case when adding agglutinating sera. 

 Corresponding to the precipitable substance in culture-filtrates of 

 B. typhostis and the Cholera germ, there must be a substance therein 

 corresponding to the agglutinin-producing substance in these bacteria, 

 for it may be noted that Widal, Levy and Bruns succeeded in rendering 



1 Kraus's earlier paper (30, iv. 1897 A'. Geselhclinft Her Aerzte in Wirn) is cited by 

 Borctet (1899, p. 2'28). I have been unable to gaiu access to the origiual. 



