XVI] VIBRIO AND SPIRILLUM 435 



culture. It follows from this that in this animal from the 

 purely intercellular substances — only dead bacillary bodies 

 having been used — substances have been produced which 

 can immunise — i.e., can act germicidally against the intra- 

 peritoneal growth and multiplication of the cholera vibrio. 

 Testing the blood-serum, " cholera serum," of such an 

 animal immunised by dead bacillary bodies only as to its 

 immunising or germicidal action against living cholera 

 vibrios after the method of Pfeiffer — i.e. mixing a definite 

 amount of " cholera serum " with an otherwise fatal dose 

 of living cholera vibrios, and injecting the mixture into the 

 peritoneal cavity of a fresh guinea-pig, at the same time 

 injecting into a control guinea-pig of the same weight the 

 same dose of living vibrios without the cholera serum — 

 it will be found that that serum exhibits in the peritoneal 

 cavity marked and definite germicidal power. R. Pfeiffer^ 

 has described numerous experiments, by which it was 

 clearly established that by repeated intraperitoneal in- 

 jections of doses of living cholera vibrios, starting with 

 non-fatal doses and gradually increasing the dose till no 

 reaction follows any longer, and the animal after the last 

 injection again gains in body-weight, the blood-serum of 

 such an artificially or " actively " immunised guinea-pig 

 has potential, powerful, germicidal power, inasmuch as 

 injected into the peritoneal cavity of a fresh guinea-pig, 

 together with an otherwise fatal dose of living cholera 

 vibrios, it produces a rapid alteration and crumbling away 

 of the vibrios,^ no multiplication of them and no disease 

 follows — that is to say, the addition of the serum of an 



^ Zeitschr. f. Hygiene ti. Infekt, vol. xvi. 



' The peculiar alteration produced in a suspension of cholera vibrios 

 by the addition of such " cholera serum " (Bordet and Durham) will be 

 described and discussed later on. 



