DIRECT EXPERIMENTS ON THE SYMPATHETIC 613 



Sequard, who published his observations in August, 1852. A few 

 months later in the same year, Bernard made similar experiments and 

 presented the same explanation of the phenomena observed. 



The important points developed by the first experiments of Bernard 

 and of Brown-Sequard were that the sympathetic system influences the 

 general process of nutrition, and that many of its filaments are distributed 

 to the muscular coat of the bloodvessels. Before these experiments, it 

 had been shown that filaments from this system influenced the contrac- 

 tions of the muscular coat of the alimentary canal. 



When the sympathetic is divided in the neck, the local increase in 

 temperature is attended with a considerable increase in the supply of 

 blood to the side of the head corresponding to the section. The increased 

 temperature is due to a local exaggeration of the nutritive processes, 

 apparently dependent on the hyperemia. There are many instances 

 in pathology of local increase in temperature attending increased supply 

 of blood to restricted parts. In an experiment by Bidder, after excis- 

 ing about half an inch (12.7 millimeters) of the cervical sympathetic in 

 a half-grown rabbit, the ear on that side, in the course of about two 

 weeks, became distinctly longer and broader than the other. 



It is easy to observe the effects of dividing the sympathetic in the 

 neck, but similar phenomena have been noted in other parts. Among 

 the most striking of these experiments are those reported by Samuel, 

 who described an intense hyperemia of the mucous membrane of the 

 stomach and intestines following extirpation of the coeliac plexus. By 

 comparative experiments it was shown that this did not result from 

 peritonitis produced by the operation. 



As regards secretion, the influence of the sympathetic is very marked. 

 When the sympathetic filaments distributed to a gland are divided, the 

 supply of blood is much increased and an abundant flow of the secre- 

 tion follows (Bernard). Peyrani has shown that the sympathetic has 

 an influence on the secretion of urine. When the nerves in the neck 

 are stimulated, the quantity of urine and of urea is increased, and this 

 increase is greater with the induced than with the constant current. 

 When the sympathetic is divided, the quantity of urine and of urea 

 sinks to the minimum. 



Moreau published in 1870 a series of observations on the influence 

 of the sympathetic nerves on the secretion of liquid by the intestinal 

 canal, which are important as affording a possible explanation of the 

 sudden occurrence of watery diarrhoea. In. these experiments the abdo- 

 men was opened in a fasting animal, and three loops of intestine, each 

 loop four to eight inches (100 to 200 millimeters) long, were isolated 

 by ligatures. All the nerves passing to the middle loop were divided, 



