96 Messrs. T. L. Brunton and J. Fayrer on the [Jan. 2.2, 



were not very carefully isolated, and it is probable that the twitchings 

 were due to direct irritation of the lumbar nerves of the right side by 

 conducted currents, especially as irritation of the left sciatic nerve caused 

 no movement in the right foot. 



The continuance of movement in the ligatured leg, after it had ceased 

 in other parts of the body, indicates that the ends of the motor nerves have 

 been paralyzed ; and this is confirmed by the production of tetanus in the 

 ligatured and absence of movement in the poisoned leg when their motor 

 nerves are stimulated. The slightness of the movements in the ligatured 

 leg when a strong interrupted current was applied to the eye, while the 

 motor nerves of the limb still retained their irritability, indicates that 

 paralysis of the reflex function of the cord had taken place. The motion 

 of the leg on turning the frog on his back afterwards, shows that the 

 higher nervous centres, through which the opposition to the change of 

 posture was manifested, retained their power longer than the cord. 



Experiment XXXVII. 



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 be- 

 tween 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 paralyzed. On irritating either fore leg by 

 electricity, or by acetic acid, slight movements occurred in the hind feet, 

 and were fully stronger in the poisoned than the ligatured limb. Irrita- 

 tion of the poisoned hind foot also occasioned 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. Irri- 

 tation applied by a strong interrupted current to the spinal cord, by elec- 

 trodes inserted in it, caused very faint twitches in both hind feet. Irrita- 

 tion 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 contractions. 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 



