NERVOUS TISSUE. 101 



gray matter, and become Fi s- 25 - 



continuous with those of 

 the anterior roots of the 

 opposite side. It has been 

 shown, too, by Mr. New- 

 port, 1 that there are other 

 fibres, which pass from the 

 posterior into the anterior 



roots of Other nerves, above Transverse Section of the Medulla. (After Stilling.) 

 and below, both On the The transverse gray fibres are the continuation of the roots 

 Same and the OPDOSite of the nerves f the longitudinal white and gray fibres are in- 

 dicated by points. 



side. 



Much, doubtless, still remains to be accomplished, before we can 

 consider views in regard to the nervous system established. Like many 

 important questions of physiology, they may be regarded as in a tran- 

 sition state ; but the zeal and activity of physiological inquirers are 

 daily throwing light upon many points; and of these there are none 

 surrounded with more obscurity than those that appertain to the nerv- 

 ous system. 



All the parts described as constituting the nervous system brain, 

 cerebellum, medulla spinalis, and nerves are formed of the primary 

 nervous fibre, the nature of which has been already described. The 

 neurine or substance of which they are constituted is soft and pulpy ; 

 but the consistence varies in different portions, and, in the whole, at 

 different ages. In the foetus it is almost fluid ; in youth of greater 

 firmness ; and in the adult still more so. This softness of structure in the 

 encephalon of the foetus is by no means inutile. It admits of the pres- 

 sure, which takes place, to a greater or less extent in all cases of par- 

 turition, whilst the head is passing through the pelvis, without the child 

 sustaining any injury. On examining, however, the consistence of dif- 

 ferent brains, it is necessary to inquire into the period that has elapsed 

 since the death of the individual, as the brain loses its firmness by 

 being kept; and ultimately becomes semifluid. It is likewise rendered 

 fluid by disease, constituting ramollissement du cerveau or mollescence 

 of the brain, to which the attention of pathologists has been directed 

 of late years, but without much important advantage to science. 



When the encephalon is fresh, it has a faint, spermatic, and some- 

 what tenacious smell. This, according to M. Chaussier, has persisted 

 for years in brains that have been dried. 



Neurine has been subjected to analysis by M. Vauquelin, 2 and found 

 to contain, water, 80*00; white fatty matter, 4*53; red fatty matter, 

 called cerebrin, 0'70 ; osmazome, 1*12 ; albumen, 7*00 ; phosphorus, 

 1-50 ; sulphur, acid phosphates of potassa, lime, and magnesia, 5-15. 

 M. Couerbe's analysis of that of the brain 3 gives, 1. A pulverulent 

 yellow fat, stearconote ; 2. An elastic yellow fat, cerancephalote ; 3. 

 A reddish-yellow oil, eleancephol ; 4. A white fatty matter, cerebrate, 



1 Philosophical Transactions, 1843, and Dr. Carpenter, 2d Amer. edit., p. 125, Philad., 

 1845. 



3 Annales de Chim., Ixxxi. 37; and Annals of Philosophy, i. 332. 

 3 Annales de Clumie et de Physique, Ivi. 160. 



