1906.] 



Special Excitable Substances in Cells. 



187 



excess of fluid removed, local contraction at the ends of the muscle where 

 no nerves are present is obtained by local application of 1 per cent, nicotine, 

 the contraction, however, is less strong than that produced by 1 per cent, 

 nicotine to the part of the muscle which does contain nerves. If this con- 

 traction is a genuine nicotine contraction like that produced in other muscles 

 by injection into the circulation of small amounts of nicotine, it shows that 

 the nicotine-receptive substance is not confined to the nerve endings. But 

 further experiments are required before it can be said that these similar 

 contractions are identical * 



I have not had time to make more than a few experiments on the effect of 

 curari on the nicotine contraction. So far it results that nicotine will still 

 cause contraction after the nerves have been paralysed by curari, but that 

 a much larger amount of nicotine is required. Whilst there is a mutual 

 antagonism between the two poisons, curari is a much more potent antagonist 

 of nicotine than it is in the fowl. 



Nicotine has a similar action on the muscles of the toad, and there is 

 a similar mutual antagonism between the action of nicotine and curari on the 

 muscles. In the toad the contraction of the flexors and extensors of the 

 arm is equal or nearly equal, so that there is little or no movement.f But 

 the cataleptic condition is usually much more marked than in the frog, and 

 affects the leg as well as the arm, though to a less extent. The fore limbs 

 can be moved about almost as if made of lead, and stay with but slight 

 return movement in any position in which they are placed consistent with 

 the arrangement of the joints and ligaments. In fig. 9 I give a photograph 



Fig. 9. 



of a toad in which the brain and spinal cord had been destroyed, and 

 1 per cent, nicotine then injected into the abdominal cavity. The limbs soon 

 became cataleptic, and the photograph is taken of one of the positions in 



* Nicotine is strongly alkaline, and I have not yet tried the effect of alkalies. Strong 

 curarisation does not abolish the action of 1 per cent, nicotine ; but this may be due to 

 the nicotine being in sufficient amount to overcome a curari effect. 



t I have not tried the effect of nicotine on the male toad during the breeding season. 



Q 2 



