298 



HITCHCOCK'S ANATOMY 



situated just within the corium, into which the nail barely 

 clips. And so numerous are these, and of so low a degree of 

 vitality, that frequently the nails grow for a short distance 

 after death. When the nails are badly injured, they are sel- 

 dom perfectly regenerated, because of the injury done to the 

 vessels and laminae. A rudimentary nail sometimes is found 

 on the second joint, when the first is destroyed. Cases are 

 also on record, where the nails have been shed and renewed 

 periodically. The nails are thickest at their most, convex 

 portion, instead of their edges, and increase in thickness from 

 the base to their free edge. They grow only so long as they 

 are cut, and among the literary class of the Chinese, who 

 never cut their nails, they are said to attain only a length of 

 two inches. The time necessary for a nail to grow its whole 

 length, varies from twelve to twenty weeks. 



522 a. Basement Membrane of the Skin. — The middle 

 layer of the skin is simply a basement membrane, and is in 

 fact the mucous layer of the epidermis. It is, however, of 

 little importance in the functions of the skin, and is believed 

 to be a separate layer merely because, when it is immersed in 

 a solution of potash in connection with the epidermis, the 

 latter is dissolved, while the former is unchanged. 



523. The Corium; its Composition; Nerves of the 

 Corium. — The Corium or internal layer is the true skin, 

 since it possesses the vitality and sensibility of this membrane, 

 and contains all its vessels. It is made up of white and yel- 

 low fibrous tissue, the white predominating, except in those 

 parts where occasional extension is required, where the yellow 

 exists in larger proportion. The blood-vessels of the corium 

 are very abundant, terminating in the minute tubes which 

 supply the sudoriparous and sebaceous glands : the proof of 

 the abundance of which we have in puncturing any part of 



Why do the nails sometimes grow after death? Why do the nails seldom grow nat- 

 urally after an injury ? At what portion are the nails the thickest ? 522 a. What is the 

 middle layer of the skin ? 523. Of what is the corium composed? What is said of the 

 abundance of blood-vessels in the corium? 



