THE EXCRETORY SYSTEM 



193 



ance, and serves, in the first place, to remove the excre- 

 mental or exhausted material from the body; and, sec- 

 ondly, to regulate the temperature by means of evapo- 

 ration of the fluid thus thrown out. For example, when 

 the body has been exposed to heat or when exercise has 

 been indulged in, perspiration is abundant, so that by its 

 evaporation the heat may be dissipated. 



FIG. 98. A normal sweat-gland, highly magnified : a, Sweat-coil, with 

 secreting epithelial cells ; b, sweat-duct ; c, lumen of duct ; d, connective- 

 tissue capsule ; e and /, arterial trunk and capillaries supplying the gland 

 (after Neumann). 



These little sweat or sudorific glands have a spiral out- 

 let upon the surface, but their entire arrangement is so 

 delicate and minute that they cannot be viewed by the 

 unaided eye. In the illustration (Fig. 98) the parts 

 showing the sudorific glands and the spiral outlet, passing 

 through the different layers of skin, have been highly 

 magnified. 



The skin is also furnished with other glandular organs, 



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