Aug. 19, 1922] SECTION OF MICROBIOLOGY. [Mnll'.f JourLl 



forms in greater number than usual, and it was thought that they might in 

 some way be connected with the lytic agent associated with this group of 

 bacilli. There was also the possibility that they might be distinct but symbiotic 

 bacilli growing only with the dysentery or other bacilli forming the culture; 

 they might be mutations, or, again, they might be special forms with special 

 work to do, like bees in a swarm, and, alone or in association with the lytic 

 agent, might prove to be of importance in connexion with the pathogenicity 

 of cultures and the production of immunity in the host. 



The work was interrupted by the war, but eventually the results were 

 published in the British Journal of Experimental Medicine (October, 1920), 

 and I shall do no more now than consider their possible relation to the lytic 

 agent. In the first place, it must be noted that these large forms occur much 

 more frequently in pathological material than they do in cultures on artificial 

 media. In cases of infantile diarrhoea and vomiting I have found them in large 

 number associated with a lytic agent in the upper part of the intestinal tract, 

 and it is only after the action of the lytic agent is eliminated that they can be 

 easily cultivated. The nature of the bacilli from such conditions is now being 

 investigated. 



Most of my experiments were carried out with the Shiga type of dysentery 

 bacillus. The first point of importance to be noted is that the large or "special 

 forms" occur in all pure cultures of bacilli belonging to the dysentery-typhoid- 

 coli group, besides occurring in cultures of the influenza bacillus and other 

 micro-organisms. Further, they are much more numerous in very young cul- 

 tures than in older ones, and practically disappear in cultures that are twenty- 

 four hours old. I observed also, in cultures that had been growing for six to 

 twelve hours, that these "special forms" were often partially dissolved. From 

 these early experiments I concluded that the bacilli normally produce "special 

 forms," and that these, when presumably of no use to the bacterial community 

 of a pure culture, are dissolved by a lytic agent which is also present, and that 

 this lysin prevents the special forms from multiplying, and interferes with 

 their isolation as growths free from the normal small bacilli. I found, however, 

 two methods by which these "special forms" could be isolated. They may be 

 obtained either by repeatedly plating out on litmus-maltose agar tubes, or by 

 growing in an emulsion of dead coliform, typhoid, or some similar bacillus, and 

 then plating out on the maltose agar medium. Three fairly distinct and stable 

 types were isolated, but it will be unnecessary to consider these in detail. The 

 chief points which I wish to bring to your notice are these: The large bacilli 

 proved to be "special forms" of the bacterium from which they were obtained, 

 and were easily agglutinated by the specific serums. I also obtained some 

 evidence that they were more pathogenic when produced by the normal bacilli 

 than after repeated multiplication by division. When isolated and grown they 

 became more resistant to the lytic agent. In most of the cultures numerous free 

 granules were present, while many of the bacilli contained similar looking 

 granules in the fusiform and round swelling which they presented. 



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