368 Transactions of the Society. 



indirect action of a theoretical toxin in producing the results 

 observed. 



The demonstration of the presence t»f this filterable virus in 

 meningococcal cultures had, in addition, this important result, that 

 it showed quite clearly that the second proposition of the text-books 

 to which I have referred — namely, that the meningococcus is a 

 bacterium with a simple life-history, beginning and endiug with 

 simple binary fission — is probably not true. It unmistakably 

 suggests, in fact, tliat the meningococcus represents one phase only 

 in the life-cycle of an organism which has not yet been described. 



The object of the present communication is, as I have said, to 

 show yet another phase in the life-history of the unknown causal 

 organism of epidemic cerebrospinal fever, though I wish to make it 

 perfectly clear that even now the whole of the mystery is not 

 cleared up, and that there are still other phases which require 

 further study. 



I shall, therefore, here confine myself to what may be learnt by 

 study of the so-called giant meningococcus, which is generally 

 believed to be a large involution form of Weichselbaum's organism, 

 but which is in reality, as you will see, not a bacterium at all — not 

 even a diseased bacterium, as your Secretary humorously would 

 put it. Before, however, Mr. Martin Duncan shows you his slides, 

 it is necessary very briefly to summarize what is at present known 

 as regards the morphology of the meningococcus and its alleged 

 involution forms. 



The meningococcus, which is usually only studied in cultures 

 on solid media, is a Gram-negative coccus, occurring singly or in 

 pairs, often with flattened opposed surfaces, sometimes in triads 

 or in tetrads, but never — the text-books say — in chain formation, 

 except as a result of accidental apposition. Heiman and Feldstein 

 also describe giant cocci, four to five times the size of a normal 

 coccus, which in diplococcoid form measures roughly 1 m. in diam. 

 These giant cocci stain intensely with whatever counterstain is 

 employed. in Gram preparations, and are believed by these authors 

 to be involution forms, and are said to be only seen in cultures up 

 to forty-eight hours old. In some cultures, as I recorded in 1914, 

 extremely minute cocci are also to be seen mixed with the 

 larger normal forms, and with the so-called giant cocci. And 

 between these very minute forms and the normal forms, inter- 

 mediate forms of every grade in size are sometimes to be made out, 

 sometimes in diplococcoid form, and at others in single coccus form. 

 In some of the normal-sized cocci, and occasionally in the giant 

 forms, a central bright spot has been described (staining deeply 

 with alkaline-methylene blue) — not to be confused with the clear 

 space, sometimes remarkably wide, which maybe seen between the 

 two members of a dividing coccus. 



The presence of the giant forms appears to receive no notice in 



