318 THE EEPTILES OF EGYPT. 
Sciences of Paris the fact that they had been able to confer on guinea-pigs partial 
immunity to viper-poison by injecting solutions of the venom attenuated by heating it 
to 80° centigrade, and that the blood-serum of animals so treated possessed antitoxic 
properties. M. Calmette 1 , a few days later, in a communication to the Biological 
Society of Paris, stated that the same serum was not merely antitoxic but preventative 
and therapeutic ; and a month later he announced to the Academy of Sciences 2 that he 
had been able to immunize rabbits, guinea-pigs, dogs, and asses against the venom of 
a variety of snakes by means of the repeated injections of small doses of venom, and 
that he had found the serum of animals so treated to be antitoxic. In June, in the 
following year, Professor T. K. Fraser 3 made known the results of his experiments 
with the venom of the cobra and other serpents, and the antidotal blood-serum of 
immunized animals, and in the following month 4 he added some further observations 
on antidotal blood-serum, or " antivenene," as he proposed to call it, and at the same 
time communicated some experiments he had made on the ingestion of cobra-venom 
by animals. 
MM. Phisalix and Bertrand 5 , in January 1896, explained their views of the relations 
that exist between the two methods by which animals may be rendered immune to the 
action of snake-venom. In both the same mechanism is at work, and it is the same 
chemical process that creates the refractory condition, the final result consisting in the 
formation of antitoxic substances — only in " vaccination " the defensive reaction of the 
organism is alone active, and not fettered by the poisons which impede it as in the 
establishment of immunity by " accoutitmance," in which the phenomenon is more 
complex. " Vaccination " they define as " accoutumance ah'egee," and " accoutumance " 
as " vaccination progressive." 
Dr. J). D. Cunningham has favoured me with the following statement regarding 
the conclusions that may legitimately be drawn from the data bearing on the establish- 
ment of artificial immunity to the action of snake-venom and the protective and curative 
properties of the serum of the blood of immunized animals. He says : — 
" 1. The action of any snake-venom on entering the system of a susceptible animal is twofold : — 
a. It gives rise to intoxication. 
6. It induces the reactive manufacture of a material counteractive of the action of its toxic 
constituents. 
"2. The latter action is persistent over prolonged periods — certainly, in the case of viperine venom, over 
periods of at least a year's duration. 
" 3. In consequence of this persistence it is possible to establish artificial immunity by means of the repeated 
administration of progressively increased doses of venom. Beginning with the administration of sublethal 
1 C. E. Soc. Biol. Paris, 1894, p. 120 et p. 201: Ann. lust. Pasteur, 1304, p. 275. 
2 C. E. Ac. Sc. Paris, 1894, p. 720. 
3 Proc. Eoy. Soc. Edinb. 1895, p. 448. 
' Op. cit. p. 471. 
5 Bull. Mus. Hist. Nat. ii. 1896, p. 36. 
