. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. NERVOUS CENTRES. (HUMAN ANATOMY. THE MENINGES.) 653 the middle line, and that to this cause the in- distinctness of the posterior fissure may be due. And this anatomical fact may be quoted as, in some degree, adverse to the theory which re- gards these columns as sensitive : for were they columns of sensation, it is probable that the preservation of their distinctness would have been more fully provided for. The anterior and posterior fissures, as Cru- veilhier remarks, leaving on each side a per- fectly symmetrical orga
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. NERVOUS CENTRES. (HUMAN ANATOMY. THE MENINGES.) 653 the middle line, and that to this cause the in- distinctness of the posterior fissure may be due. And this anatomical fact may be quoted as, in some degree, adverse to the theory which re- gards these columns as sensitive : for were they columns of sensation, it is probable that the preservation of their distinctness would have been more fully provided for. The anterior and posterior fissures, as Cru- veilhier remarks, leaving on each side a per- fectly symmetrical organ, serve to demonstrate the existence of two spinal cords, one for eacli side of the body, and both presenting a perfect resemblance of form and structure. There are no other fissures in the cord besides those just described. Several anato- mists regard the lines of origin of the anterior and posterior roots of the nerves as constituting distinct fissures. But a little careful examina- tion will readily convince any one that there is no real separation of the nervous substance of the cord corresponding to these lines, and that there is no anatomical indication of a sub- division into columns or segments in connexion with them. When the roots of the nerves have been removed on each side, nothing is seen but a series of foramina or depressions correspond- ing to the points of emergence of the nerve- fibres, of which the roots are composed. The most natural subdivision of the spinal cord is that which is obviously indicated by its internal structure. In examining a transverse section (fig. 376), we observe that the interior Fig. of each lateral portion is occupied by grey matter, disposed somewhat in a crescentic form. The concavity of the crescent is directed out- wards ; its anterior extremity is thick, and is separated from the surface of the cord by a con- siderable layer of white nervous substance. The grey matter is prolonged backwards and out- wards in the form of a
Size: 1757px × 1422px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
