BACTERIA SUSCEPTIBLE TO BACTERIOPHAGY 267 



more (and this was recognized by Lemos Monteiro and by Kraus) 

 such a culture containing added filtrate spread upon agar yields nothing 

 having the appearance of plaques. 



This phenomenon does not present any of the characters of bacteri- 

 ophagy, but is a reaction which has been studied for a long time by many 

 authors and was first described by Gamaleia. As a matter of fact, 

 Pesch^"^ has dealt with the erroneous interpretation of this phenomenon 

 in a recent paper entitled "The Anthrax Pseudo-bacteriophage." 



A number of authors, of whom Quiroga was the first^^^ have described 

 a phenomenon taking place in agar cultures of B. pyocyaneus, and again, 

 this reaction has been likened to bacteriophagy. Some of those who 

 have observed this change appear, however, to have some doubt on this 

 point, for example, Combiesco and Magheru^^^ speak of it as a phe- 

 nomenon ''resembling bacteriophagy." 



Hadley,^^^ in particular, has studied this transformation in pyocyaneus 

 cultures, and it has been found to take place with a very large number of 

 B. pyocyaneus strains. When cultured on agar spots appear having an 

 irridescent lustre. These for a time gradually extend and finally end 

 by being re-covered by the surrounding culture. Within the area of 

 the spots the agar is not bare but is covered by a layer which is vitreous, 

 transparent, and greenish in color. Examined under the microscope 

 this vitreous material is found to be composed of fine granules which 

 stain red by the Giemsa method. The vitreous material, filtered 

 through a candle, appears to induce the formation of irridescent spots. 

 I say "appears to," for strains spoken of as "susceptible" produce these 

 same areas spontaneously without the addition of filtrate. 



This is by no means a phenomenon of dissolution but is rather a 

 phenomenon of fragmentation.* It appears, comparing this description 

 with that of the Twort phenomenon, that it is due to the phenomena of 

 bacterioclysis discovered by Twort. 



But, one might ask, can not the two phenomena be caused by the 

 same principle? We have seen that this objection can not be raised 

 with regard to what takes place with the staphylococcus since Gratia 

 has shown that this organism shows, when acted upon by the bacteri- 

 ophage, not the phenomenon of bacterioclysis of Twort, but the phe- 

 nomenon of bacteriophagy and this proceeds in a manner absolutely 

 identical with that which occurs when the bacteriophage reacts upon 



* Those writing upon this subject, Hadley among others, naturally speak of 

 "lysis," a term which no longer has any precise meaning in biology. Certainly 

 this term is very convenient, partly because of its lack of precision. 



