434 SEPARATION OF THE CUTICLE. 



well as to defend it.* And it is probable tbat the sebaceous 

 matter is secreted for the purpose of preserving the cuticle in a 

 state of flexibility. 



As the cuticle is capable of confining fluid, and resisting the 

 action of chemical agents, it is surprising that epispastics and 

 rubefacients should act through it, upon the skin, with so much 

 certainty as we find they do; and that cantharides should pro- 

 duce vesications, when applied dry. 



The thickness of the cuticle on every part of the body is 

 much increased by long continued pressure, forming corns and 

 excrescences of its own nature. By this cause also it is ren- 

 dered very thick on the palms of the hands and soles of the 

 feet ; although it is originally thicker there than in other parts. 



It is said that, after long boiling, these thick portions of cuti- 

 cle may be separated into distinct lamina. 



In the living subject, the cuticle, when immersed in warm 

 water, seems to absorb some of that fluid ; as is evinced by the 

 hands when they have been long in that situation ; and also by 

 those parts of the skin to which poultices have been applied. 



Notwithstanding the uniform adhesion of the cuticle to the 

 cutis, it is observed, in the living subject, to be separated, and 

 formed into vesicles, by a variety of causes, viz. 



1. Pinching of the skin, or violent mechanical irritation ; such 

 as laboring with hard instruments. 



2. By the application of cantharides, and certain other sub- 

 stances which produce vesications. Sometimes these sub- 

 stances appear to inflame the skin ; but on other occasions the 

 vesication is produced while the skin appears unchanged in 

 color, and free from inflammation. The process appears dif- 

 ferent from that of simple inflammation ; for certain rubefa- 

 cients often inflame the skin considerably without vesicating or 

 blistering it. 



3. Boiling heat will, very generally, produce vesication. 



4. Certain diseased processes seem to occasion vesication in 



* This property of the cuticle is rendered very apparent in attempting to dry 

 anatomical preparations with the skin on, in which the student will fail, unless 

 the cuticle is previously removed by maceration. p. 



