CHOLESTERINE AND PHOSPHORUS. 275 



of the epidermis ; that is to say, they arise from nuclei on the spaces 

 which are nearest to the supply of "blood, and gradually undergo devel- 

 opment as they prepare for connection with the tubular tissue, assuming 

 the place of cells that have discharged their function and are undergoing 

 disintegration. This gradual passing onward and wearing away recalls 

 the changes in the structure of the cuticle. 



To two of the substances thus met with in these examinations of the 

 nervous system our attention may be profitably directed. Chole rin 

 These are cholesterine and phosphorus. Of the former we and phospho- 

 can not have failed to remark that it is a constant ingredient rus * 

 in the product of the action of the liver. It is a lipoid, and is found in 

 biliary calculi ; and though it may be regarded in one sense as an excre- 

 mentitious body, since it occurs in faecal matter, yet it also appears as 

 a normal constituent of the blood. It may therefore be inferred, if the 

 opinion of its existence in the white substance of Schwann be correct, 

 that it is one among the various functions of the liver to prepare this 

 body. Of phosphorus it might be said, that it, among the chemical 

 elements, is most strikingly characterized in its active state by the in- 

 tensity of its affinity for oxygen. On this depends its quality of shining 

 in the dark, a quality which has given it a name ; but by many agents, 

 such, for example, as exposure to a particular temperature, and especially 

 to the light of the sun, it may be thrown into a condition so completely 

 passive that its chemical energies disappear. The doctrine that was pre- 

 sented in explanation of the destruction of one part of the system by the 

 air introduced by respiration while another is protected therefrom, as de- 

 pendent on the allotropic condition of those parts, is presented here again 

 in discussing the destruction and repair of the nervous tissue ; for it is 

 only when it is ready to be removed that the phosphorized constituent 

 assumes the active state, and in so doing gives rise to the development 

 of force. On this view, it would appear that such phosphorized com- 

 pounds are obtained from the vegetable kingdom in the food in a passive 

 state, the tissues of plants having deoxidized them under the influence 

 of the sunlight, which simultaneously has thrown them into the condi- 

 tion of inactivity, and perhaps it is the assumption of that very condition 

 that is the fundamental cause of their deoxidation. 



By the aid of the conclusions to which we have come respecting the 

 function of nerve-tubes and vesicles, as betrayed by their an- Functions of 

 atomical structure, we shall not have much difficulty in ex- n ^ e 1 ^ e " o s n and 

 plaining the offices of nervous arcs presently to be described, sidered eiec- 

 The results at which we thus arrive, from a consideration of tricall y- 

 those cells, are singularly fortified by the electrical experiments of Gal- 

 vani, Volta, Nobili, and especially those of Volkmann. Among these, 

 the three following are of primary importance : 



