THE NERVOUS SYSTEM. 435 



is no more than happens if any important part of the body re- 

 ceives an injury, or if any unimportant part is extensively in- 

 jured ; if a leg is crushed or falls into gangrene, the whole 

 system suffers, though a leg may be removed and the system be 

 none the worse. 6 The application of stimuli to the encephalon 

 or spinal chord excites the action of the heart, and, even after 

 its removal, of the capillaries : but stimulus to any important 

 part will stimulate others ; and even to an unimportant part, if 

 the stimulus is strong. The passions do the same : but they 

 influence all parts ; and, though a due excitement of the passions 

 is necessary to the health of all parts, it is only because the 

 body thrives best as a whole when each part fully performs its 

 functions. Compression of the brain causes slowness of the pulse 

 and constipation ; but this is only such a sympathetic influence 

 as may exist between any parts. It appears, from Dr. Brachet's 

 experiments, that irritation of the brain affects other parts by 

 means of the pneumono-gastric ; for its division prevented all 

 effects of the brain upon the heart. f 



The removal of a piece of the pneumono-gastric, or the de- 

 struction of that part of the chorda oblongata with which it is 

 connected or of a considerable portion of the chorda spinalis, 

 heavily impairs the functions of the lungs and of the stomachs, 

 putting a stop, some say to the muscular action of the stomach, 

 others to the secretion of gastric juice and to digestion. The 



e The hearts of six decapitated robbers beat strongly and regularly for nearly 

 half an hour; and after a man's cerebrum and cerebellum were blown off by an 

 explosion of fire-arms, the respiration and circulation continued above half an 

 hour. (Dr. Brachet, 1. c., p. 80. sq.) 



f Reck. Exper. p. 118. 



g Le Gallois, 1. c., and many former writers. 



Dr. Philip conceives this influence of the brain and spinal chord to be gal- 

 vanic, as he prevented the ill effects of the removal of a piece of the pneumono- 

 gastric nerve upon the lungs and stomach, by supplying these organs with gal- 

 vanic influence. (1. c. p. 210. sqq.) Dr. Brachet, however, equally succeeded by 

 mechanically irritating the end of the portion of the divided nerve running to the 

 stomach. 



Division of the nerve had no effect if the divided ends lay opposite each other, 

 although a quarter of an inch intervened. (Dr. W. Philip, 1. c. p. 226. sqq.) 



A mechanical stimulus, or a substance in its nature stimulating, applied to 

 the brain about the origin of the nerves, excites contractions in the voluntary 

 muscles ; a substance in its own nature stimulating excites the heart and capil- 

 laries, when applied to any part of the brain or spinal chord, but requires to 

 be applied to a considerable portion. (Dr. Philip, 1. c.) 



G G 3 



