486 THE BACTERIOPHAGE AND ITS BEHAVIOR 



Fejgin has not, however, drawn any very definite conclusions from 

 her studies, certainly because of a false conception of bacteriophagy. 

 She simply states that there must exist some relation between typhus 

 exanthematicus, B. proteus Xig, and the bacteriophage. 



Having recourse to the facts which have been presented in the first 

 part of this text, the etiology of typhus fever could be explained as 

 follows: The B. proteus X19, developing as a mixed culture with the 

 bacteriophage, becomes transformed into its micellar ultrabacterial 

 infravisible form,* and these ultrabacteria, capable of reproducing in 

 this form, would really be the agents of typhus exanthematicus. 



The bacteriophage protobe is not a providential agent found in the 

 intestine, in order to assure the "defense" of the individual who harbors 

 it against the bacteria which try continually to invade it. The bacterio- 

 phage protobe is simply a parasite of bacteria, occurring by preference 

 in the intestinal tract because it there finds the most favorable conditions 

 for its development, and in this it behaves like all living beings which 

 multiply in that place where they are best able to exercise their faculty 

 of assimilation. The bacteriophage does not exist for an "end," and if, 

 generally, it is a cause of recovery from disease because it is able to 

 exercise its faculty of assimilation of pathogenic bacteria, it is equally 

 able in other cases to be an indirect cause of disease. 



For an analogy we have only to turn to the white blood ceU. The 

 phagocyte is a "salutary agent" when it engulfs a microbe which it can 

 digest; it is an "agent of destruction," — even of death, — when, en- 



* We have seen in Part I that this is a common phenomenon which may be 

 observed with all bacteria, and that the micellar form which is produced occurs 

 as a reaction of the bacterium to the presence of the bacteriophage. 



In speaking of these ultrabacteria I suggested a hypothesis on the subject of 

 the agent of scarlet fever. Opportunities to apply this hypothesis are abundant. 

 For example, it would be strange if the Leptospira discovered by Noguchi is 

 really the agent of yellow fever (a disease with which I am familiar from having 

 studied it in Yucatan). I have spent weary days with my eye to the micro- 

 scope examining slides of the organs and tissues of individuals dead of yellow 

 fever, and never yet did I see a single Leptospira. All of this would be ex- 

 plained if the true parasite is a filtrable form of the Leptospira of Noguchi. 

 As a matter of fact, the spirochetes are undifferentiated microbes, which must 

 be, like the bacteria, micellar plasmodia.'*^ 



Insofar as typhus exanthematicus is concerned, there is an opportunity to 

 attempt treatment by the injection of a mixture of different races of the bac- 

 teriophage, virulent for B. proteus Xig, if among the races available there are 

 any virulent for the proteus strain found in the patient. 



