INTRODUCTION 17 



This author reviews the different hypotheses which he consid- 

 ered as possible causes in effecting the transformation of the cul- 

 tures. The substance of vitreous appearance, he says, certainly 

 contains an enzyme which is destroyed at 60°C. On the other 

 hand, the material is susceptible of continued cultivation, since 

 it can be indefinitely transplanted on a culture of the micrococ- 

 cus. May it be a cultivable enzyme? May it be living proto- 

 plasm of indeterminate form? May it be an ancestral form of the 

 micrococcus which can not be cultivated in this form but which 

 incites the normal micrococcus to take this form of regression? 

 Or, may it be an enzyme secreted by the micrococcus itself which 

 produces thus its own destruction, with the formation of a new 

 quantity of destructive enzyme? May the substance of vitreous 

 appearance be composed of a filtrable virus which may be itself 

 the virus of vaccinia or a filtrable virus entirely without patho- 

 genicity derived from the air and which enters the micrococcus 

 cultures by passing through the cotton which closes the tubes? 

 Twort did not choose from these several hypotheses which he 

 formulated, although it seemed to him most probable that the 

 vitreous substance was produced by the organism, the micrococ- 

 cus, itself. He indicated further, that he had no idea as to the 

 relation which might exist between the bacillus or the micrococ- 

 cus, the vitreous material, and the disease. 



The phenomenon observed by Twort has been thus emphasized 

 because it involves a serial activity, and because, on the other 

 hand, it is hardly probable that the cause is a bacteriophage. 

 Indeed, it has been proved that with a true bacteriophage active 

 against Staphylococcus albus the phenomenon described by Twort 

 can not be reproduced. The very peculiar characters, and indeed, 

 the characteristics presented by the phenomenon observed by 

 Twort render confusion of this principle with the bacteriophage 

 impossible. The difference in thermal death points, amounting 

 to 15°C, between the two principles (the bacteriophage becomes 

 inactive only at about 75°C.) is alone sufficient to differentiate 

 them. According to some experiments which I have performed 

 the facts observed by Twort may be ascribed to a fragmentation 

 of the bacteria; it is only necessary to use the ultramicroscope to 

 see that the "vitreous substance" is composed of very minute 

 cocci. 



