BACTEEIA SUSCEPTIBLE TO BACTERIOPHAGY 265 



by his own description. I would refer the reader to the introduction 

 of the present volume where I have incorporated, in exienso, the descrip- 

 tion of the phenomenon given by Twort. 



The only objection which might be made is this: that the phe- 

 nomenon of bacteriophagy, that is to say, the attack of the bacterium 

 by the bacteriophage, may manifest itself with Gram-negative bac- 

 teria by a dissolution and with the Gram-positive bacteria by a simple 

 fragmentation. Gratia (without questioning this, however) has shown 

 that this objection can not be considered for he has shown that a true 

 bacteriophagy of the staphylococcus occurs in absolutely the same way 

 as bacteriophagy with other bacteria, with the Shiga dysentery bacillus 

 for example. 



It is, then, Gratia^"*^ who unquestionably should be credited with 

 first demonstrating a bacteriophage virulent for the staphylococcus and 

 who, at the same time, clearly proved that bacteriophagy manifests 

 itself in an absolutely identical fashion for both Gram-positive cocci 

 and for Gram-negative bacilli. 



Gratia^^^ has the further merit of discovering a race of the bacterio- 

 phage attacking all strains of the staphylococcus; — albus, aureus, and 

 even citreus, and as I have shown, M. tetragenous also. With such a 

 bacteriophage, a bacterial species so heterologous as are the staphy- 

 lococci, behaves exactly like a homologous species. 



I will not describe here bacteriophagy with the staphylococcus; the 

 characteristics of the phenomenon are identical with those observed 

 with the bacilli. Furthermore, in the majority of instances I have used 

 the dysentery bacillus and the staphylococcus as examples in the experi- 

 ments illustrating the facts presented in Part I of this text. 



The staphylococcus may acquire a resistance just as do the other 

 bacteria. But with staphylococci this phenomenon presents a single 

 interesting peculiarity. In artificially mixed cultures (that is to say, 

 in those composed of staphylococci with an acquired resistance and 

 bacteriophage corpuscles) along with typical staphylococcus forms 

 isolated cocci, diplococci, and chains of a few elements may be seen. 

 By the serial cultivation of a Staj^hylococcus aureus possessing an ac- 

 quired resistance in pure suspensions of the bacteriophage (the poly- 

 virulent strain H of Gratia) I have obtained cultures formed of fine 

 sedimented agglutinates, the medium remaining clear. Under micro- 

 scopic examination one sees only isolated cocci, diplococci, and strep- 

 tococcus-like chains, the longest being composed of 1 1 elements, but there 

 is no arrangement of cells resembling a typical staphylococcus grouping. 

 Transfers of these cultures to agar remain sterile. 



