RELATIVE STABILITY OF LIVING MATTER 309 



of a strength (2 per cent to 3 per cent) which is fatal to most 

 protoplasm." 1 Davenport adds : 



One general law of high resistance is worthy of notice : an organism which 

 produces an albuminoid poison is strongly resistant to that poison. Thus 

 Fayrer has shown that venomous serpents are not destroyed by the secretion 

 of their poison glands when it is injected into them ; and Bourne has shown 

 that scorpions are not injured by their own venom. 1 



It is a well-known fact that immunity from a poison is gained 

 by frequently repeated and gradually increased doses, beginning 

 with a minimum quantity. Thus users of tobacco, alcohol, opium, 

 chloral, etc., are able to withstand, indeed require for comfort, 

 amounts that would be exceedingly injurious, even fatal, to one 

 not acclimated to its use. It is said that arsenic eaters may 

 take with impunity as much as 0.4 grams, or four times the 

 lethal dose. 1 The same results are obtained experimentally. 

 Sewall inoculated pigeons with rattlesnake poison. He found 

 that while no unacclimated birds could withstand one drop of a 

 6.8 per cent solution of venom in glycerin, yet by commencing 

 with a weak solution they were enabled to resist four drops of 

 the fatal solution. Kanthack in the same way acclimated two 

 rabbits and a hen to serpent's venom. 2 



This method is entirely similar to the one employed to render 

 man immune to smallpox, hydrophobia, anthrax, diphtheria, and 

 other dangerously infectious diseases. The virus is cultivated 

 successively in the body of a lower animal, until its virulence is 

 much reduced. Then, beginning with an exceedingly attenuated 

 solution, the patient is inoculated repeatedly with virus of increas- 

 ing strength until complete immunity is secured, or until the 

 full strength may be endured without serious consequences. 



Ehrlich experimented with white mice in an endeavor to dis- 

 cover the upper limits of artificial immunity. Commencing with 

 a 0.0005 P er cent solution of ricin, which was the strongest 

 they could endure and live, the strength was gradually in- 

 creased to 0.2 per cent in twenty,one days, or to four hundred 

 times the natural lethal strength. Thus it may be said that 

 these mice had acquired in the period of twenty-one days an 



1 C. B. Davenport, Experimental Morphology, Part I, p. 28. 2 Ibid. p. 29. 



