246 STUDIES l\ IMMUNITY. 



injected must be of definite morphology to give rise to distinct 

 sensitizers. Substances without any cellular structure have already 

 been used for injection. Bordet,*for example, obtained a serum that 

 precipitates cow's milk by injecting this milk into rabbits. Was- 

 sermaimt obtained similar results with several varieties of milk. 

 Tchistovitch} and Bordet § injected various foreign sera into rabbits 

 and obtained corresponding precipitating sera. Mijers|| produced 

 -era that precipitate egg albumin, sheep-scrum globulin, ox-serum 

 globulin, and pepton. These experiments have been repeated and 

 extended by other authors whose work need not be mentioned. 



But hitherto only a precipitating property has been described 

 in the serum of animals injected with foreign non-cellular organic 

 substances. It seemed to us desirable to ascertain whether an 

 animal immunized in this way does not produce substances similar 

 to antimicrobial and hemolytic sensitizers as well. For the demon- 

 stration of these sensitizers we have used the method of Bordet 

 and Gengou, which, as already stated, is based on the fixation of 

 the alexin by a sensitized cell. We have endeavored to determine 

 whether this fixation may be produced by the serum of rabbits in- 

 jected with such fluids as cow milk, hen-egg albumin, pure horse 

 fibrinogen, and dog serum heated to 55 degrees, and, finally, with 

 the serum of guinea-pigs immunized against rabbit serum (55 de- 

 grees) ; in other words, we have endeavored to determine whether 

 the sera of these treated animals contain a sensitizer as well as a 

 precipitin for the substances injected. 



The serum of rabbits vaccinated against cow milk. — We injected 

 rabbits with relatively large amounts of cow milk previously heated 

 to 70 degrees for one-half hour. They were given, in successive 

 doses, 10, 10, 12 and 12 c.c. at intervals of 7 days. They were bled 

 1-1 days after the last injection and the separated serum heated 

 for a half hour to 56 degrees; this serum we refer to as Serum 

 rabbit > milk 56 degrees. Fresh normal rabbit serum freed from 

 corpuscles, after standing overnight at room temperature (16° C) 

 was uniformly employed as alexin. 



* Mechanism of agglutination, p. 142. 



t Deutsche med. Wochenschr., 1899, No. 80. 



% Tchistovitch, Annales de lTnstitut Pasteur, March, 1899. 



§ Bordet, see pp. 142, 175. 



|| Centralblatt fur Bakt., 1900, XXVII. 



