350 IMMUNITY AND CURATIVE INOCULATIONS 



immunity resulting from the introduction into the Hving 

 body at intervals of a series of doses of a poison gradu- 

 ally increasing strength has been called " Mithridatism," 

 and animals and men so treated have been said to be 

 " mithradatised." The toleration of poisonous drugs — 

 such as tobacco and alcohol, and even of mineral poisons, 

 such as arsenic — was, until lately, regarded as merely a 

 special exhibition of that habituation or " adaptation by 

 use" which living things often show in regard to some of the 

 conditions of their life. Unusual cold, unusual heat, un- 

 usual moisture, salinity or the reverse, unusual deprivation of 

 food, unusual muscular effort may be tolerated by animals 

 without injury provided that they have been " gradually 

 accustomed " to the unusual thing, or, in other words, that 

 the unusual has been gradually made the usual ; so that 

 there is a saying that eels after a time even get used to 

 being skinned. There was no attempt to explain the 

 details of this process of habituation ; it was assumed to 

 be a part of the general " educability " of living matter. 



The study of the education of living matter, in regard 

 to various conditions which can act upon it, has yet to be 

 further carried out, but the way in which the poisons made 

 by disease germs and the like, and the disease germs 

 themselves, are dealt with in the blood and tissues has, on 

 account of its urgent importance, from a medical point of 

 view, been already profoundly studied by experimental 

 and microscopic methods of late years. The old notion 

 as to " mithridatism " was that an animal or a man would 

 have to be separately prepared and " immunised " by 

 habituation for every distinct kind of poison. We now 

 know that this is not the usual way in which Nature 

 confers immunity to poisons. Most astonishing, and at 

 first sight magical or mysterious, powers exist in the 

 living protoplasmic cells in and around the blood of 

 man and higher animals, which enable their possessors to 



