240 NATURAL SCIENCE. March, 1S93. 



different from those with which we started : by selection a new stock has been pro- 

 duced, in some cases it is more virulent, in other cases less so. 



The dependency of the protective influence of inoculation upon the rate of 

 multiplication of the pathogenic microbe will be seen when we leave ectasines and 

 anectasines out of account and consider only phagocytosis. 



Whatever the nature of the stimulus may be, Cohnheim's demonstration that 

 diapedesis of leucocytes is the dominant phenomenon of the resultant inflammation, 

 together with their action as phagocytes in presence of microbes, may be taken for 

 granted. At the seat of inflammation, then, there is a terrific battle between two 

 armies, the microbes attacking, the phagocytes defending. In both armies there is 

 a great mortality, and the ultimate result of the battle depends upon the rate at 

 which each army is reinforced — i.e., upon the rate of multiplication of microbes on 

 one hand and on the rate of migration of fresh phagocytes to the scene of action on 

 the other. So long as the microbes have the best of it the fever increases. So soon 

 as the phagocytes become sufficiently numerous to cope with the microbes, destroying 

 them more rapidly than they are produced, so soon does the fever begin to abate. 



The hypothesis in question is that the stimulus of the poison not only increases 

 the diapedesis of leucocytes (i.e., transportation of the defending army of phagocytes 

 to the scene of action), but also leads to an increased rate of production of leucocytes 

 within the body, so increasing not only the size of the standing army provided for 

 the defence of the body, but also increasing the rate at which new recruits are 

 added to it. 



If the microbe army introduced be only an " attenuated virus," then that army 

 will not have time to increase to unmanageable dimensions before the phagocytes 

 appear on the scene ; the disease will, therefore, be easily checked, and the net result 

 will be an increase in the strength of the army of phagocytes, whose duty is the 

 protection of the animal against the attacks of armies of microbes. 



I am not a pathologist, and only bring this to Mr. Bulman's notice that he may 

 subject it to that same criticism which has apparently destroyed the two theories 

 with which he dealt in his article in the current number of Natural Science. 



C. Herbert Hurst. 



Owens College, Manchester, 

 February 13, 1893. 



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ERRATA. 

 P. 86, line 39. For " pashs " read " parks." 

 P. 87, line 20. For " Ohazal " read " Dhuyal." 



