THE PRESENT EVOLUTION OF MAN — PHYSICAL 231 



means by which higher organisms are brought into 

 harmony with an exceedingly complex environment ; but 

 it is highly incredible that phagocytes or any other cells, 

 when acted on by this or that toxin, should suddenly 

 develop the power of producing this or that anti-toxin, a 

 complex chemical substance which exactly antagonizes 

 another highly complex chemical substance, the particular 

 toxin presented, but no other. It would be as reason- 

 able to attribute the resistance offered by trained 

 skin-cells to heat to the production of an anti-pyretic 

 substance, or the resistance offered by other kinds of 

 trained cells to the action of nicotine, alcohol, opium, 

 arsenic, &c., to the production of specific anti-toxic 

 substances. 



When therefore the toxins (freed from the micro- 

 organisms) of diphtheria are injected into the horse, it 

 is highly improbable that there is elaborated in that 

 animal an anti-toxic substance which exactly antagonizes 

 the poison, and which, dissolved in his blood-serum, 

 when injected into man, for that reason renders the 

 latter resistant to the disease. On the contrary, it is 

 probable, since the injection of immunized blood-serum 

 apparently does tend to produce increased powers of 

 resistance in man, that the toxins are altered in the 

 horse, perhaps by intracellular digestion, as suggested 

 by Dr. Hunt ; ^ are rendered less virulent, are so altered 

 that the phagocytes of the man are able to react to them, 

 and thus to attain a position of advantage, whence they 

 are able to react to the unaltered virus, to accomplish 

 by successive efforts that which they are unable to ac- 

 complish at a single effort. It is very improbable that 

 the animal body is a sort of " magic bottle " which pro- 

 duces particular anti-toxins at need, but very probable, 

 judging by analogy, that its cells are able to vary 

 gradually so as to adapt themselves to that change in 

 ^ British Medical Journal, September 16, 1893. 



