320 THE EEPTILES OF EGYPT. 
other animals with similar results. The most recent conclusion drawn by Professor 
Fraser 1 from these experiments is that a degree of protection against lethal doses of the 
venom of the cobra is acquired in a few hours by the administration of the venom by 
the stomach, whereas it requires several weeks to establish an immunity to the venom 
when it is injected under the skin. He also suggested that the results of the experi- 
ments on the ingestion of cobra-venom by animals probably afforded an explanation of 
the alleged immunity to the effects of snake-poison claimed by snake-charmers and 
certain sects of men. 
The immunity induced by the ingestion of cobra-venom he explained on the theory 
that the poison when it reaches the stomach becomes the subject of an analytical 
process, in which the poisonous constituent of the venom fails to be absorbed by the 
blood, whereas the constituent or constituents which are antidotal pass into the blood 
and so protect the animal against otherwise lethal administrations of venom. 
Dr. D. D. Cunningham 2 , who has investigated this subject, records two experiments 
the results of which are seemingly in direct conflict with those attained by Professor 
Fraser. A monkey (Macacus rhesus) was treated with doses of cobra- venom by the 
mouth for a period of sixteen months. The ingestion of the venom gave rise to no 
appreciable symptoms of intoxication, but a minimum lethal dose of cobra-venom 
finally administered by subcutaneous injectiou, but how long after the last dose by the 
mouth had been administered does not appear, produced symptoms of intoxication after 
an interval of 4-| hours, and death 5i hours later. Another monkey of the same 
species received by the mouth a dose of 0'2 gramme, i. e. 80 times the amount of a 
minimal lethal dose when administered subcutaneously, but no appreciable result 
followed. After the expiry of 24 hours, when - 0025, or a minimal lethal dose, of dried 
venom was subcutaneously injected symptoms of intoxication developed within two 
hours and death followed in 5-| hours later on. Dr. Cunningham, on the strength of 
these two experiments, says that the second shows that the ingestion of an amount of 
venom 80 times as great as that constituting a lethal dose when entering the system 
directly is incapable of producing any appreciable effect on the action of a minimal 
lethal dose administered subcutaneously 24 hours later, while the first experiment proves 
that the prolonged and habitual ingestion of smaller quantities of venom is equally 
inefficacious. He explains the conflicting results of his own and Professor Eraser's 
experiments on the supposition that, in those cases in which protective effects seem to 
follow the ingestion of large quantities of venom, they may possibly have arisen in 
connection with the presence of breaches of continuity or other abnormalities in the 
surface of the mucous membrane of the alimentary tract allowing of the absorption 
of a certain amount of crude venom, rather than by an analysis of the venom by the 
normal digestive apparatus as suggested by Professor Fraser. 
1 Eoyal Instit. G. Britain, March 1896. 
2 Sc. Mem. Med. Officers Army of India, part x. (Calcutta, 1S97). 
