303 



CHAP. XIX. 



THE NERVOUS SYSTEM. 



\V^E now arrive at the animal functions those which consist of 

 feeling and the exertion of a will, those, therefore, which, in 

 their nature, must be peculiar to animals. 



The organs of these functions are, the cnccphalon, spinal chord, 

 and nerves. These, together with bodies called ganglions, con- 

 stitute the nervous system. 



The encephalon, or brain, is encased in the cranium ; the spinal 

 chord, or improperly, spinal marrow, or spinal prolongation of the 

 brain, in all the vertebrae, down to the first or second lumbar ; 

 the nerves pass through openings in the skull, between the verte- 

 brae, and in the sacrum, and run in all directions through the 

 system ; while the ganglions are disseminated in the head, neck, 

 and trunk. 



The encephalon is the largest solid organ found in the cavities of 

 the body, except the liver. Its substance is not firm, and on ex- 

 posure to the air grows very soft. It consists of a pulpy and a 

 fibrous portion. Its more external part, and some internal parts, 

 are pulpy, and of various shades of ash colour and yellowish 

 brown. The chief portion is fibrous and white. It is, therefore, 

 said by some to consist of a cortical or cineritious, and of a 

 medullary or white, portion : but what is not white is not always 

 cortical, neither is its hue always cineritious ; and the white fibrous 

 portion is totally different from what is properly called marrow. 

 Gall, therefore, more properly, says it consists of a pulpy and a 

 fibrous portion.* 



* " We could wish that the term medulla were banished from the nervous 

 system. The functions of nerves are totally different from those of marrow, and 

 infinitely more noble. Besides, the idea of marrow always excludes fibrous 

 structure." (Anatomie et Physiologie du Systeme Nerveux, et du Cerveau en par- 

 ticulier, 4 vols. 4to. Paris, 1810 19, with an atlas of 100 plates Vol. i. p. 49.) 



While some had said that the white part was all blood-vessels, others that it 

 contained none, some that it, as well as the cineritious part, was all globules, 

 some that it was solid, others tubular, Leuwenhoeck, Vieussens, and Stenon, 



/ 



