lY.-MOEBID ANATOMY OF THE SKIX. 



§ 285. In studying the structural alterations associated with 

 the various disorders to which the skin is liable, it is of advan- 

 tao-e to consider that organ as made up of the epidermis and 

 papillary body on the one hand, of the corium and subcutaneous 

 areolar tissue on the other ; the morbid anatomy of the cutaneous 

 2;lands and the hair being considered by itself in an Appendix.* 

 Tlie papillary body, apart from its other physiological functions, 

 is the matrix of the epidermis. The two structures constitute a 

 vegetative whole; and their continuity is strikingly apparent 

 when, as in the case of most diseases, the vegetative relations 

 of the parts are disturbed. So too the glands, the hair and the 

 nails are all liable to special diseases of their own. Of course I 

 neither care, nor do I wish to deny that the disorders of the 

 various constituents of the integument pass into one another by 

 manifold transitions, that they may coexist, that they may be 

 pathologically identical. No classification of natural objects can 

 lay claim to be absolute ; we must endeavour to select that w^hich 

 fits the actual facts most closely. Thus for instance, a similar 

 analysis of the structural constituents of mucous membranes 

 would be far from conducing to a better knowledge of their 

 pathology. 



1. Diseases op the Epidermis and the Papillary 



Body. 



a. Inflammation. 



§ 286. The integument of the body is peculiarly exposed by 

 its position to all external influences of a hostile nature. We 

 are not therefore surprised to find a long series of skin- 



* The nails will be dealt with among the horny overgrowths of the 

 epidermis, the keratoses. 



