320 



METHODS OF IDENTIFICATION AND STUDY 



germ free filtrate is rapidly drawn through into the 

 test-tube receiver. 



Raising the Virulence of an Organism. If it is 



desired to raise or "exalt" the virulence of a feebly 

 pathogenic organism, special methods of inoculation 

 are necessary, carefully adjusted to the exigencies of 

 each individual case. Among the 

 most important are the following : 



1 . Passage of Virus. The inocula- 

 tion of pure cultivations of the organ- 

 ism into highly susceptible animals, 

 and passing it as rapidly as possible 

 from animal to animal, always select- 

 ing that method of inoculation 

 e. g., intraperitoneal which places 

 the organism under the most favor- 

 able conditions for its growth and 

 multiplication. 



2. Virus Plus Virulent Organisms. 

 The inoculation of pure cultiva- 

 tions of the organism together with 

 pure cultivations of some other mi- 

 crobe which in itself is sufficiently 

 virulent to ensure the death of the 



experimental animal, either into the 

 .bio. 161 -Martin s ., . 



filtering apparatus same situation or into some other 



oTfluidf 11 quantities part of the body. By this associa- 

 tion the organism of low virulence 

 will frequently acquire a higher degree of virulence, 

 which may be still further raised by means of "pas- 

 sages" (vide supra). 



3.^ Virus Plus Toxins. ^hQ inoculation of pure 

 cultivations of the organism into some selected situa- 

 tion, together with the subcutaneous, intraperitoneal, 

 or intravenous injection of a toxin e. g., one of those 

 elaborated by the proteus group either simultane- 

 ously with, before, or immediately after, the injection 



