294 



Leaving then this impossible line of treatment, the 

 only one present to the minds of those who are so 

 willing to instruct medical men on medical matters, 

 we will now discuss one which is possible, and which 

 has proved eminently successful in certain allied 

 conditions in man and other mammals. I mean the 

 treatment by serums. It will be remembered that 

 on several occasions I have spoken of the leucocytes 

 or white corpuscles of the blood as "devouring" the 

 bacilli after having previously killed them and 

 neutralised their toxins with the chemical alexines or 

 antitoxins which the former had thrown out for the 

 purpose, while at the same time the normal number of 

 the white corpuscles is relatively much increased, with 

 the object of successfully coping with the invading 

 force. The thoughtful reader then at once grasped 

 the idea that these processes constitute Nature's own 

 cure, and that it was in this direction alone that there 

 existed the barest chance — if any — of the " simple 

 cure." It struck him immediately that if it could be 

 done the obvious remedy was to increase the total 

 quantity of antitoxins in the blood of the affected 

 bird. And he was right — so far indeed as the principle 

 went. Whether however it is practicable to apply this 

 principle to birds, we shall be better able to determine 

 later on. In the meantime we will see as an illustra- 

 tion how it is carried out in the case of some of the 

 diseases attacking the higher animals, in which it is 

 applied. 



If we turn back to one of the earlier chapters 

 where I discuss the question of immunities, we shall 

 find that as a general rule one attack of an infective 

 disease confers immunity against another attack for a 

 longer or shorter period of time, equally whether the 

 attack was a mild or a virulent one. The explanation 

 lies — at any rate in some diseases — in the fact that 

 after the recently augmented blood antitoxins have 



