Facts bearing on acquired immunity 217 



fluids of immunised animals, affords a very valuable indication of the 

 simultaneous presence of cytase and of specific fixative. As we have 

 already stated, at the commencement of this account of the acquired 

 immunity of guinea-pigs against the cholera vibrio, Pfeiffer's pheno- 

 menon is manifested in the peritoneal fluid of these animals in a 

 very short time (5 to 20 minutes) after the inoculation of the vibrios. 

 This proves that in this fluid the two substances really occur together, 

 and that the fixative and the cytase are in solution in the plasma of 

 the exudation. Is it the same in every part of the body of immunised 

 guinea-pigs ? If, instead of introducing the cholera vibrio into the 

 peritoneal cavity, we inject it into the subcutaneous tissue or into the 

 anterior chamber of the eye of these animals, Pfeiffer's phenomenon 

 does not make its appearance. The vibrios, isolated or collected into 

 small clumps, do not undergo granular transformation ; they keep 

 their normal vibrio form and remain alive much longer than in the 

 peritoneal cavity. Some of them may be found still living 24 hours 

 after subcutaneous injection and several (4 6) days in the anterior 

 chamber of the eye. Xor can Pfeiffer's phenomenon be observed when 

 the cholera vibrio is introduced into the oedema of the foot, pro- 

 duced in consequence of the slowing of the circulation, the vibrios 

 remaining alive for a fairly long time. These facts clearly indicate 

 that in the fluid thrown out in passive oedema, just as in the aqueous 

 humour of the eye or in the subcutaneous tissue, the two substances 

 necessary to set up the granular transformation are not present. Are 

 both of them absent or only one ? This question is easily answered [229] 

 on adding to the fluids mentioned normal guinea-pig's serum, a 

 serum which, by itself, is incapable of producing Pfeiffer's pheno- 

 menon. Bordet 1 has made these experiments and found that when 

 to the fluid of the passive oedema of the immunised guinea-pig 

 normal serum is added, this fluid transforms the cholera vibrio into 

 granules, but does so in less degree than does the serum of the same 

 immunised guinea-pig, when heated to 55 56 C., to which normal 

 serum has likewise been added. There is, then, reason to conclude 

 that the fluid of the oedema does not contain any cytase, but contains 

 a certain quantity of cholera fixative, less, however, than that which 

 is found in the blood serum. As to the aqueous humour of the eye 

 of immunised animals, analogous experiments have demonstrated 

 that it contains neither of the two substances necessary for the 

 production of Pfeiffer's phenomenon. 



1 "Contribution k 1'etude du serum chez les animaux vaccines," Ann. Soc. d. sc. 

 nat. et med. de Bruxelles, 1895, t. iv. 



