POISON OF SOME INDIAN VENOMOUS SNAKES. 61 



Experiment XXXYII. 



November 29th, 1872. — The sciatic nerve of the left leg of a 

 frog was exposed ; and a double ligature being passed under it 

 round the limb, the whole of the tissues except the bone were 

 then divided and removed between the ligatures. A fraction of 

 a drop of cobra-poison, diluted with -|-per-cent. salt solution, 

 was injected into the lymph-sac. After about two hours the 

 animal seemed paralysed. On irritating either fore leg by 

 electricity, or by acetic acid, slight movements occurred in tlie 

 hind feet, and were fully stronger in the poisoned than the 

 ligatured limb. Irritation of the poisoned hind foot also occa- 

 sioned twitches both in it and the non-poisoned foot. Twitches 

 did not invariably occur. No twitching of the fore paws was 

 noticed on irritation of the hind feet. A ligature was then 

 passed round the poisoned hind leg, and the tissues divided, as 

 in the non-poisoned one, and the animal left a little longer. 

 Irritations again applied had a similar result to the former, but 

 the contractions in the non-poisoned limb were sometimes 

 stronger than in the other. Irritation applied by a strong 

 interrupted current to the spinal cord, by electrodes inserted in 

 it, caused very faint twitches in both hind feet. Irritation of 

 the lumbar nerves in the abdomen caused very faint twitches in 

 the feet. Irritation of the exposed sciatic nerve of the non- 

 poisoned limb by an interrupted current caused strong con- 

 tractions. Similar irritation of the poisoned sciatic caused 

 much weaker contractions. Direct irritation of the muscles by 

 interrupting a constant current caused contractions of nearly 

 equal strength in both. 



The dose of poison in this experiment was small, and it was 

 given in a much diluted form. The fact that an interrupted 

 current applied to the sciatic nerve of the poisoned limb had a 

 much slighter effect than the same current applied to the 

 sciatic nerve of the non-poisoned limb, while the interruptions 

 of a constant current by opening and shutting a key caused 

 the poisoned and unpoisoned muscles to contract with apparently 

 the same force, shows that a small dose of the poison causes a 

 considerable amount of paralysis of the ends of motor nerves, 

 while the muscles are but little affected. 



