Aug. 19, 1922] SECTION OF MICROBIOLOGY. [ MEmcAL Journal 



does the lytic agent attack some members of a culture before it attacks others, 

 but individual members may be pitted and eroded, and particularly is this so 

 with certain large forms of dysentery bacilli which I shall consider later. Again, 

 it is well known in the case of all bacteria that certain members of a culture 

 are more resistant to chemicals and to specific lysins produced in animals, and 

 it may well be that the lytic action on the bacteria starts from a number of 

 distinct points because these points happen to contain specially susceptible 

 micro-organisms, and it is only when the action is started and the lytic sub- 

 stance increases in quantity and in concentration that the more resistant 

 members become lysed. 



Then there are the very interesting experiments of Professor Bordet and Dr. 

 Ciuca. These workers found that when a lysin was produced by an animal 

 against a coliform bacillus, this lysin not only dissolved up fresh cultures of the 

 coliform bacillus, but the lytic effect could be transmitted from culture to cul- 

 ture. These results certainly do not favour the view that the lytic agent is a 

 definite living micro-organism. Moreover, there are my own original experi- 

 ments where, after obtaining normal growths of micrococci for a number of 

 generations, eventually some fresh subcultures started to become lysed, 

 apparently spontaneously. But these experiments appear to me to be evidence 

 not only against the view that the lytic material is a definite living organism, 

 but also against the view of Bordet and Ciuca that the lytic agent arises from 

 an association of the bacterium with cells from the animal body. d'Herelle 

 has also obtained the lytic agent by associating bacteria with filtrates of soil, 

 etc., and I agree with him that these experiments do not support Bordet's 

 view, although at the same time I do not think they support the view that the 

 lytic agent is a definite living micro-organism. The apparent spontaneous pro- 

 duction of the lytic agent in some of my pure cultures is, I think, evidence 

 against both the views mentioned. It may, of course, be argued, as I men- 

 tioned at the time, that my cultures were never really quite free from the lytic 

 agent, but if this view is accepted regarding my repeatedly plated cultures, 

 then it is reasonable to suggest the same regarding the cultures used by 

 d'Herelle and by Bordet. 



Recent experiments, in fact, have in no way changed my views, and I repeat 

 my original opinion regarding the lytic agent of the micrococcus— namely, that 

 "the possibility of its being an ultramicroscopic virus has not been definitely 

 disproved," and that "it seems probable, though by no means certain, that the 

 active transparent material is produced by the micrococcus"; and I hold the 

 same view regarding the lytic agent which various workers and myself have 

 found associated with the dysentery-typhoid-coli group of bacilli. 



However, as I have already pointed out, it is just possible that an ultra- 

 microscopic virus may be of the nature of an enzym.e, and if so, the original 

 source of such a virus might be the cell it infects: in remote ages possibly a 

 normal enzyme which has gradually developed to take on a pathological action 

 as it has passed through an infinite number of generations of cells, either 



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