248 THE SOLIDS. 



with each other, whereby it forms a' distinct and continuous 

 membrane, and in the paucity of granules dispersed through- 

 out the cells. 



The epidermis also stands in precisely the same relation 

 with the parts beneath it as the epithelium ; thus, it has no 

 structural connection with those parts, and receives neither 

 blood-vessels nor nerves from them, but is simply dependent 

 upon them for the plasma which is continually escaping from 

 the blood-vessels of the true skin. This want of structural 

 connection is shown by the fact that a portion of the cuticle 

 may be detached without its removal occasioning either pain 

 or haemorrhage. 



This separation of the epidermis from the dermis fre- 

 quently takes place during life, as from a burn, scald, or 

 blister, or from the effusion of serum, the result, not of in- 

 jury, but of disease. After death and on the commence- 

 ment of decomposition, the epidermis may be detached in 

 large masses, the prolongations sent down to the sebaceous 

 and sudoriferous glands also coming away with it. 



The epidermis does not merely cover the whole external 

 surface of the body, but sends processes into its various out- 

 lets, as the mouth, nose, rectum, vagina, and male urethra; 

 these prolongations soon lose, however, the characters of epi- 

 dermis, and acquire those of epithelium. 



The epidermis likewise sends down processes into the 

 sebaceous and sweat glands, and which, forming a perfect 

 tube, serve to convey the secretions of those glands to the 

 surface, on which they open as raised and rounded papillae, 

 with central depressions and apertures. (See Plate XXIII. 

 figs. 1 and 2.) 



A sheath of epidermis likewise encircles the base of each 

 hair. 



The number of these infundibuliform processes and sa- 

 lient papillse which open on the surface is immense, and may 

 be stated at about 3000 to the square inch, which, com- 

 puting the number of square inches of surface in a man of 

 average size at 2500, would give 7,500,000 for the entire 

 surface of the body. 



