

PATHOLOGICAL STATES OF THE SKIN. 493 



3. Hence the skin is an aerating organ, as accessory to the lungs; 

 oxygen being absorbed directly into its bloodvessels. 



4. The skin is a secreting organ, affording the sweat and the 

 sebaceous fluid. 



5. The contraction of the skin is shown in the cutis anserina (so 

 called), the erection of the nipple, and the wrinkling of the skin of 

 the scrotum and the penis (p. 477). 



6. But the skin manifests its most important function as the 

 organ of the sense of touch. And it is a singular fact that all 

 points of the skin are sensitive, though nerves cannot be demon- 

 strated in all, or even in the majority, of the papillae. Kolliker, 

 however, finds that the same point is sometimes sensitive, and some- 

 times not so. Probably the nervous plexus at the base of the 

 papillae, and not those in the latter alone, are the media of the 

 sensibility of the skin. The various modifications of tactile im- 

 pressions, as those of pressure, warmth and cold, of orgasm, of tick- 

 ling, pricking, burning, and pain, are not well accounted for. The 

 thickness of the cuticle of a part, the paucity or abundance of 

 nerves, the superficial or deep position of the nerve-fibres, the 

 thickness or delicacy of their neurilemma, &c., must doubtless be 

 taken into consideration; and, on the other hand, also, the agents 

 producing the sensations named. 



Pathological States of the Skin. 



1. Pathological colorations of the epithelium of the skin have 

 already been mentioned (p. 137). A local thickening of it from 

 continued pressure constitutes the clavus or corn, and its other 

 morbid states are mentioned on page 247. 



In the vesicular diseases of the skin (pemphigus, &c.), an exuda- 

 tion of plasma, occurring from the vessels of the corium into the 

 stratum Malpighii, causes a limited elevation of the cuticle. In 

 eczema, herpes, and miliaria, the vesicles are very small. In ich- 

 thyosis the cuticle is much thickened. 



II. The corium may (1) become generally atrophied in wasting 

 chronic diseases (tuberculosis, syphilis, &c.); it becoming thinner 

 and smoother on its surface, and the sebaceous and perspiratory 

 glands, and the hairs, even, becoming atrophied or disappearing. 

 Local atrophy may be produced by pressure and other causes. 



2. New formations of areolar tissue in the corium (papilloma, 

 &c.) have already been described (p. 247). 



3. The corium is also the seat of disease in all the exanthemata 

 (scarlatina, rubeola, &c.) ; most of them affecting the papillary por- 

 tion more especially. 



4. In variola, papulae, J[so called) are first formed by exudation 



