66 ON THE NATURE AND ACTION OF THE 



Distance 9'5, very faint contraction in both tibial and 

 gastrocnemic muscles. Apparently equal in both legs. Heart 

 quite still and contracted. 



On testing the irritability of several of the frogs used in 

 these experiments on the ensuing day, the ligatured leg was 

 found to contract on irritation of the sciatic nerve, or of the 

 muscles directly. The muscles of the poisoned leg did not 

 contract, either when irritated directly or through the nerves. 



Experiment XLII. 

 May 20th, 1873. — In order to test the action of cobra- 

 poison on the ends of the motor nerves, without disturbing the 

 experiment by ligaturing one leg, two frogs were taken of as 

 nearly as possible the same size. Both were very small ; but 

 No. 1 was somewhat larger and stronger than No. 2. The 

 sciatic nerve was exposed in one thigh of each frog and placed 

 on the hook electrodes used by Marey for his myograph. By 

 means of a Pohl's commutator, with the cross pieces taken out, 

 an interrupted current could be sent at will through either 

 nerve. The distance of the secondary from the primary coil at 

 which the first faint contraction took place in the muscles of 

 either nerve was noted. 



Distance of primary from 



when the coil was at such a 

 distance (19 ?) that no move- 

 ment occurred in leg when 

 nerve was irritated. 



