114 DISEASES OF THE SKIN AND HAIRS. 



2. Diseases of the glands of the skin. 



3. Diseases of the hair-follicles and hair. 



Mr Erasmus Wilson explains that, by the expression ' gene- 

 ral superficies of the skin,' is to be understood not only the 

 apparent surface of the skin, but also that portion of the 

 surface which forms the vascular walls of the follicles and 

 excretory ducts of glands. 



Mr Wilson shows the fundamental relationship between 

 different skin diseases which are apparently very different 

 from each other. He says, " In considering the pathological 

 phenomena of inflammation of the superficies, we find ERY- 

 THEMA (signifying redness), or simple vascular congestion; 

 LICHEN (signifying roughness), or congestion of the pores 

 and superficial portion of the follicles, producing a tumid 

 state of those parts, and constituting pimples ; ECZEMA (to 

 boil out, or seethe), a vascular congestion accompanied by 

 effusion of liquor sanguinis, lymph, or serum, and giving 

 rise to vesicles; IMPETIGO, a similar pathological condition, 

 resulting in the production of pus and pustules; and FuRUN- 

 CULUS, vascular congestion, with loss of vitality of a part of 

 the structure of the skin." 



Mr Wilson goes on to say, that " as simple inflammation 

 is capable of, and is the active agent in, producing the seve- 

 ral morbid conditions of the skin, we are not surprised at 

 finding that they are mutually convertible; that an ery- 

 thema, for example, may become a lichen by the develop- 

 ment of pimples, an eczema by the evolution of vesicles, or 

 an impetigo by the production of pustules. In the same 

 manner, the pimples of lichen having subsided, the lymph or 

 ichor of eczema being dried up, and the pus of impetigo 

 exfoliated in crusts, there may remain behind a chronic ery- 

 thema, to which another term, namely psoriasis, has been 

 applied." 



