48 ELEMENTARY PHYSIOLOGY. VII. 



DEMONSTRATIONS. 



1. Prolonged contraction of muscles combined 

 with catalepsy. The brain and spinal bulb of a frog 

 are destroyed, and 2 c.c. of 1 p.c. nicotine injected with 

 a hypodermic syringe into the dorsal sac. The frog is 

 placed on its back with the head supported so as to 

 prevent fluid running out of the dorsal sac. In a minute 

 or two, the toes are separated, and there is twitching 

 in the muscles of the legs. A little later the fore limbs 

 become stiff, and they are usually raised in slight jerks 

 to meet across the sternum. When the fore legs have 

 ceased to move, if they are pulled gently up at right 

 angles to the body, they stay in this position. Similarly 

 new positions given to the fore arms and feet are more 

 or less retained (catalepsy). The body reflexes are gradu- 

 ally abolished owing to paralysis of the motor nerves. De- 

 struction of the spinal cord does not stop the catalepsy. 



In 20 to 30 minutes from injecting the nicotine, the 

 tonic contraction becomes less, and the fore legs gradu- 

 ally become flaccid. 



If the spinal bulb is not destroyed, the first effect of 

 nicotine will be to cause crawling movements. 



The catalepsy is due to an altered physical condition 

 caused by nicotine in the neural region of the muscle 

 fibres; the elasticity of the muscle being much di- 

 minished. The catalepsy of hysteria in man is similar 

 in external appearance, but it is due to an action of the 

 central nervous system, and the muscles (so far as is 

 known) are in tetanic and not in tonic contraction. 



2. Peristaltic action of intestine and ureters. 



