1 68 BIOLOGICAL PHYSICS 



its containing membrane, and perhaps to the sebaceous 

 glands, we may trace some of these materials, as well as, 

 it may be, the final disposal of the substance composing 

 the axis cylinder of the nerve fibrils with the broken- 

 down constituents of its containing tube, or wall. 



The ubiquitous structures represented by the epidermal 

 covering of the cutaneous envelope, the epithelial and 

 endothelial linings of the hollow spaces of the body, 

 constitute the " scene," and afford the " theatre," wherein 

 the ultimate disposal of the materials used up by nervine 

 activity is effected, and where the separation and excretion 



of the effete and toxic residuum of 

 these materials are carried out. 



The process of separation, and 

 excretion, may be accomplished 

 through the circulatory agencies 

 belonging to the nervous system 

 itself, and, it may be, also by the 

 aid of other agencies, emanating 



FIG. 64. PART OF THE RETI- r j i_ i ^.u u 



CULUM FROM THE SPIN \i. rrom, and belonging to, the haemal 



S 35 SS, *** system. Thus, there may be a 



dual security provided for the 



maintenance of cutaneous perspiration, and transpiration, 

 resulting from the co-existence of a nervine, and haemal, 

 sudoriferous feeding mechanism, connected with the 

 sweat glands, in virtue of which a state of cutaneous 

 circulatory equilibrium is made possible, and temperature 

 evenly sustained ; sweating may, therefore, be due to 

 one, or both, of these sources of supply acting alone, 

 or simultaneously, and, accordingly, the sweat may 

 somewhat alter in character and composition according 

 to which of the sources is the more active for the time 

 being. The profuse perspiration produced by active 

 physical exercise is somewhat different from that pro- 

 duced under states of mental excitement, the former 

 arising in hyperaemic conditions of the skin, and the 

 latter, it may be, in anaemic conditions of that texture ;. 

 the opposite conditions of active physical exertion, and 

 extreme physical collapse, being thus characterised by 

 profuse action of the sudoriferous apparatus. 



Sweat is, therefore, a product of nervine, or haemal,. 



