THE PRESENT EVOLUTION OF MAN — PHYSICAL 249 



disturbance of the system produced by them is small 

 when compared to the disturbance produced by the 

 toxins of acuter diseases — e.g. anthrax or diphtheria. 

 The microbes, therefore, since Natural Selection has so 

 little developed their toxins, and since they are able so 

 long to resist the phagocytes, must, like those of tuber- 

 culosis, possess considerable "personal vigour," and 

 must therefore considerably injure and enfeeble the 

 phagocytes in the physical struggle waged between 

 them. As a result, the phagocytes of an infected 

 individual are at a great disadvantage, as compared to 

 the i^hagocytes of an individual in whom the toxins 

 alone are present, and therefore are much less able to 

 vary in a fit direction, are much less able to respond 

 appropriately to the stimulation of the toxins ; so that 

 when, at a given stage of the disease, the phagocytes of 

 the latter, uninjured by a physical struggle, are quite 

 able to destroy the microbes, should they find entrance, 

 the phagocytes of the former are quite unable to do so 

 speedily, and recovery from the disease is delayed to a 

 later period. 



Children born of parents recovered from syphilis and 

 immune to it are not themselves immune, though non- 

 infected children born of a mother not yet recovered are 

 certainly immune, as we may prophesy with confidence. 

 Here again we light on a fact of the highest importance, 

 the significance being this — that while in the non- 

 infected embryo of a diseased mother there are phago- 

 cytes which react to the stimulation of the toxins 

 derived from the microbes in the mother, whereby the 

 immunity of the child is secured, in the ovum (or the 

 spermatozoon) of an infected person there are no phago- 

 cytes ; in it therefore there can be no fit reaction, and 

 therefore the individual into which it may subsequently 

 proliferate is not immune. 



