type of respiration . . . which will enable it to survive in the j ^ 

 relatively low tension of oxygen found in the tissues of a living 

 host; and it must be possessed of ferments which will enable 

 it to utilize the sources of carbon and nitrogen furnished by 

 the host. It must find the food substances in solution (as after 

 trauma) or be able to produce chemical changes which will 

 bring about a solution of the tissue, for, under normal condi- 

 tions the cells . . . contain little or no free water. 



Emphasizing again his experiments on the inability of bac- 

 teria to grow upon media too gelatinized (since such contained 

 no free water) while they grew luxuriantly in the "waters of 

 syneresis," squeezed off by the media, he went to one of his 

 great generalizations: 



In quite an analogous manner the bacteria which are capable 

 of producing an extensive local edema are the species which 

 spread most rapidly . . . B pestis, B anthracis, B tularense, 

 B welchii, B cedematis maligni, the streptococci of erysipelas, 

 scarlet fever, epidemic sore throat, strangles in horses . . . 

 The mechanism by which these bacteria produce the hydration 

 of the tissues which enables them to grow and multiply is not 

 clear. 



Actually, Wherry was clearer on this subject than anyone 

 else had been before him: "The filtrates of cultures contain 

 substances which produce local congestion and edema . . . 

 these might be amines." 



He supported his conclusion by collection of the much scat- 

 tered evidence which showed that disease-producing organisms 

 quite regularly produce amines, and that these increase the 

 swelling of laboratory proteins just as they increase what he 

 had called "tissue hydration." Infestation with bacteria was 

 thus turned to infection by them, if endowed with proper life 

 capacities; and the harmless "saprophyte" suffered reclassifi- 

 cation as a "pathogen." 



But these bacterial soups, besides thus making for a swelling, 

 also produced immunity. This could not be due to their 

 content of amines, for such compounds are of too simple a 

 chemical composition to produce it — things much more com- 

 plicated, like the complete and original albuminous materials 

 from which the amines come, were required. Wherry said: 



