THE PROBLEMS OF THERAPEUTICS 177 



which are to a certain extent antidotal to one another. Thus in 

 jaborandi we have two alkaloids one of which, pilocarpine, stim- 

 ulates secretion enormously, whilst the other, jaborine, paralyzes 

 secretion, so that an extract of the jaborandi plant containing 

 them in proper proportion might possibly appear inactive although 

 it contained both alkaloids in considerable amount. The same is the 

 case with poisonous mushrooms which contain a poisonous alkaloid, 

 muscarin, which produces severe irritation of the intestine and an 

 atropine-like substance which antagonizes it. Opium likewise con- 

 tains alkaloids having very different actions, some being almost purely 

 narcotic and others purely convulsant. The animal body seems to 

 have a wonderful power of accommodating itself to the action of 

 man}^ poisons and this is very marked indeed in the case of opium. 

 Many persons who begin with a small dose increase this gradually to 

 an enormous extent so that they are able to take with impunity 

 many times the ordinary lethal dose. The organism has a certain 

 power of storing up antidotal substances within itself and Dr. Cash 

 and I were able, by feeding animals with potash, to render them less 

 susceptible to the poisonous action of barium, but except in the case 

 of arsenic the organism seems to have but little power of becoming 

 accustomed to inorganic poisons. It is different, however, in the case 

 of organic poisons as shown by the resistance to the action of alcohol 

 acquired by habitual topers and to morphine by habitual opium- 

 eaters. A similar resistance may be acquired to snake-venom and to 

 the toxins produced by microbes; and here it does not seem to be 

 merely that the cells of the organism become accustomed to the 

 poison, but that the organism forms an antidote, not only in suffi- 

 cient quantity to neutralize the poison which is introduced, but 

 actually in such superabundance that serum separated from the 

 blood of an animal which has become immune to the action of snake- 

 venom or of toxins will neutralize the effect of the venom or 

 toxins in another animal. So great is this power that Sir T. R 

 Fraser has found by inoculating an animal with gradually increasing 

 doses that it may at length completely resist the action of fifty times 

 the ordinary lethal dose of snake-venom, and in an experiment of 

 M. Calmette I have seen an animal which had received the serum 

 from such an immunized animal remain healthy and well, although 

 another one which was inoculated at the same time and with the same 

 dose of snake-venom was dying from the effect of the poison. 



When horses are inoculated with successively increasing doses 

 of the toxin of diphtheria, their blood acquires a high antitoxic 

 power, and the use of the serum of such blood injected into patients 

 suffering from diphtheria has robbed this disease to a great extent 

 of its awful power. Hydrophobia is another disease which has been 

 to a great extent deprived of its terrors by Pasteur's method of 



