DIRECT EXPERIMENTS ON THE SYMPATHETIC. 641 



plexuses of the uterus and Fallopian tubes, of the ureters and of the blood- 

 vessels. 



Direct Experiments on the Sympathetic. The experiments of Pourfour 

 du Petit (1712-1725) were the first to give any positive information regard- 

 ing the action of the sympathetic system ; and these observations may be 

 taken as the starting-point of a definite knowledge of the physiology of the 

 sympathetic, although they showed only the influence of the cervical portion 

 upon the eye. In 1816, Dupuy removed the superior cervical ganglia in 

 horses, with the effect of producing injection of the conjunctiva, increase of 

 temperature in the ear and an abundant secretion of sweat upon one side of 

 the head and neck. These experiments showed that the sympathetic has an 

 important influence upon nutrition, calorification and secretion, In 1851, 

 Bernard divided the sympathetic in the neck on one side in rabbits, and 

 noted on the corresponding side of the head and the ear, increased vascularity 

 and an elevation in temperature of 7 to 11 Fahr. (4 to 6 C.). This con- 

 dition of increased heat and vascularity continues for several months after 

 division of the nerve. In 1852, Brown-Sequard repeated these experiments 

 and attributed the elevation of temperature directly to an increase in the 

 supply of blood to the parts affected. He made an important advance in 

 the history of the sympathetic, by demonstrating that its section paralyzed 

 the muscular coat of the arteries, and farther, that Faradization of the nerve 

 in the neck caused the vessels to contract. This was the discovery of 

 the vaso-motor nerves, and it belongs without question to Brown-Sequard, 

 who published his observations in August, 1852. A few months later in the 

 same year, Bernard made analogous experiments and presented the same ex- 

 planation 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 blood-vessels. Before these experiments, it had been 

 shown that filaments from this system influenced the contractions of the mus- 

 cular coats of the alimentary canal. 



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

 perature is always attended with a very great increase in the supply of blood 

 to the side of the head corresponding to the section. The increased tem- 

 perature is due to a local exaggeration of the nutritive processes, apparently 

 dependent directly upon the hypersemia. 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 excising about 

 half an inch (12-7 mm.) 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 analogous phenomena have been noted in other parts. Among the 

 most striking of these experiments are those reported by Samuel, who de- 

 scribed an intense hyperaemia of the mucous membrane of the stomach and 



