836 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



given somewhat in detail in previous sections. The most important 



function which it fulfills in the animal 

 economj' is in the regulation of the 

 calibre of the blood-vessels. This has 

 already been described under the subject 

 of the Circulation. 



The sympathetic likewise possesses a 

 number of independent functions either 

 in the way of inhibiting or stimulating 

 various processes which ordinarily are 

 controlled bj' the cerebro-spinal nerves. 

 As examples of such action may be men- 

 tioned the automatic ganglia of the heart, 

 the mesenteric plexuses of the intestine, 

 and the sj'mpathetic plexuses of the 

 uterus, Fallopian tubes, and ureters. Of 

 course, here, also, the share of the sym- 

 pathetic in regulating the calibre of the 

 blood-vessels occupies an important 

 position. 



The sympathetic nerve, also, in addi- 

 tion to such functions in which this nerve 

 may be regarded as an efferent nerve, 

 carrying impulses from the central ner- 

 vous system, likewise acts as an afferent 

 nerve; as, for instance, in the conduction 

 of sensory impressions from the abdominal 

 viscera through the splanchnic nerves. 

 It has further been claimed that the 

 various ganglia of the sympathetic may 

 themselves act as reflex centres, "but no 

 clear demonstration of this statement has 

 ever been reached. Its strongest advo- 

 cate was Claude Bernard, and he pointed 

 to the submaxillary ganglion as an illus- 

 tration of such an independent action on 

 the part of the sympathetic ganglia. 

 We have already discussed the grounds 

 for doubting the correctness of this 



Fio. 362.— Sympathetic Nerve of statement. 

 the Horse. (Flesch.) 



a, main trunk: I; rami communicantos : c, Probably tile maill function of tile 



gray commissural fibres ; </, roots of the splaach- 



nicWve; spj, splanchnic nerve. ganglia of the sympathetic nervous 



system is to modify impulses coming from the central nervous 



