CHAPTER IY. 



EXCRETION ACTION OF THE SKIN. 



Differences between the secretions proper and the excretions Composition of 

 the excretions Mode of production of the excretions Discharge of the 

 excretions Physiological anatomy of the skin Extent and thickness of 

 the skin Layers of the skin The corium, or true skin The epidermis 

 and its appendages Desquamation of the epidermis Physiological anat- 

 omy and uses of the nails and hair Development and growth of the nails 

 Varieties of hair Number of the hairs Roots of the hairs, and hair-fol- 

 licles Structure of the hairs Sudden blanching of the hair Uses of the 

 hairs Perspiration Sudoriparous glands Mechanism of the secretion of 

 sweat Quantity of cutaneous exhalation Properties and composition of 

 the sweat Peculiarities of the sweat in certain parts. 



IN entering upon the study of the elimination of effete 

 matters, it is necessary to appreciate fully the broad distinc- 

 tions between the secretions proper and the excretions, in 

 their composition, the mechanism of their production, and 

 their destination. These considerations are again referred 

 to, 1 for the reason that they have not ordinarily received 

 that attention in works upon physiology which their impor- 

 tance demands. The mechanism of excretion is insepara- 

 bly connected with the function of nutrition, and forms one 

 of the great starting-points in the study of all the modifica- 

 tions of nutrition in diseased conditions. 



Taking the urine as the type of the excrementitious 

 fluids, it is found to contain none of those principles included 

 in the class of non-crystallizable, organic nitrogenized mat- 

 ters, but is composed entirely of crystallizable matters simply 



1 See chapter I. on " Secretion in General." 



