EFFECT OF SNAKE VENOM UPON THE NERVOUS SYSTEM, ETC. 131 



is unable to produce the slightest reflex response. In this stage the heart may 

 be beating feebly, but the whole circulation is thrombosed. If, however, even 

 thrombosis be excluded from the case by heating the venom before the injec- 

 tion, the result is the same. A series of direct experiments was performed on 

 frogs to demonstrate the paralytic effect of the venom upon the reflex activity 

 of the spinal cord. The method for testing the reflex activity was to dip the 

 foot every 5 minutes into a 4 per cent sulphuric-acid solution, washing 

 off the acid from the foot after each dipping. The venom in a dose of 

 o.oi gm. in 5 c.c. was introduced into the dorsal lymph-sacs of the frog, and 

 it was deprived of its fibrin ferment by heating the solution to 85 C. before 

 use. After envenomization, the brain was destroyed and the animal hung 

 by its lower jaw. The latent period between the application of the stimulus 

 and the response was noticed and the results show that the latent period in 

 control frogs varied from 0.6 to i second during the first hour, but required 

 3 to 4 seconds when tested the next day. On the other hand, the poisoned 

 frogs gradually lengthened the latent period and finally gave no response 

 within from 20 to 25 minutes after the injection of the venom. The heart 

 in these poisoned frogs ceased to beat after 15 to 20 minutes. In a number 

 of frogs with the hearts excised no response was obtainable after 25 to 30 

 minutes. 



Martin examined the irritability of the terminations of the phrenic nerves 

 and also of the motor nerves of the brachial plexus of rabbits after the injec- 

 tion of the venom of Pseudechis, but found no change in their function of 

 transmitting the impulses to the muscles. On the other hand, he met with 

 some instances in which the contraction of the muscle of the poisoned leg 

 (in frog) was caused by far less stimulus than that of the other leg, a phe- 

 nomenon not infrequently observed also by some other investigators and 

 accounted for by the suppression of the circulation by the ligature. 



HYDROPHHNJE. 



The venom of sea snakes is a very powerful one and is unparalleled in any 

 of the land snakes. As already mentioned in the description of symptoms 

 produced by the venom of Hydrophiinas, its main effects are on the nervous 

 system. 



Leonard Rogers l made careful studies on the venom of Enhydrina vala- 

 kadien, and our present knowledge concerning its physiological action is 

 largely due to his investigations. 



In warm-blooded animals (cats and rabbits) there is a primary paralysis 

 of the respiratory center in quickly fatal cases of poisoning. In the more 

 protracted cases of toxication primary failure of respiration is accompanied 

 by a marked rise of blood pressure due to the increasing venosity of the blood. 

 If no artificial respiration is adopted the blood pressure suddenly falls some 

 minutes after the cessation of respiration, but with artificial respiration there 



1 Rogers. On the physiological action of the poison of the Hydrophidae. Roy. Soc. Proc., 1904, 

 LXXII, 305. 



