THE NERVOUS SYSTEM. 139 



218. The singular situation and form, before alluded 

 to, of certain parts of the brain, and likewise some 

 pathological phenomena, have induced physiologists 

 to suppose certain parts, in particular, the seat of the 

 soul. Some have fixed upon the pineal gland,* others 

 the corpus callosum,t the pons Varolii, the medulla 

 oblongata, the corpora striata, and the water of the 

 ventricles, which washes against the origin of some 

 nerves. Others not contented with one spot, have 

 assigned particular parts of the brain for individual 

 faculties and propensities. (G) 



219. The energy of the whole nervous system does 

 not depend solely upon the brain. The spinal marrow, 

 and even the nerves, are possessed of their own powers, 

 which are sufficient to produce contractions in the 

 muscles. These powers are probably supported by 

 the vascular cortex of those parts (212). In man, the 

 powers proper to the nerves are less, and those depend- 

 ent upon the brain greater, than in brutes, especially 

 the cold-blooded. 



220. The office of the whole nervous system is two- 

 fold, To excite motion in other parts, especially in the 

 voluntary muscles, of which we shall hereafter speak at 

 large; and to convey impressions made upon the 

 organs of sense to the brain, and there to excite per- 



* The Cartesian hypothesis appeared to receive some weight from the 

 dissection of maniacs, in whom the pineal gland was found full of calcareous 

 substances. But more careful observation shewed, that, after the twelfth year, 

 it was generally filled with a pearly s uid, in the healthiest persons, though very 

 seldom in brutes. Sommerring, De lapillis rel prope vel int.ro. glandular* 

 pinealf.m sitis, s. de acervulo ccrebri. Mogunt. 1785. 8vo. 



t The prerogative of this part was ably refuted by Zinn, E.rp. circa corpus 

 caltosum, cerebellum, dtiram mcningon, in v it-is animulibus instil. Gott. 

 17-19. 4to. 



