356 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



the germinal epithelium. In fact, embryologically 

 this layer is to be considered as a part of the horny 

 laminae rather than interposed between the horny 

 and the soft laminae, as is done by most authors. 

 The hoof wall, on the other hand, grows exclusively 

 from the epithelial surface of the coronary cushion, 

 and its downward progress is synchronous and uni- 

 form with the growth of the horny laminae, as de- 

 scribed above. The provisional horn that appears 

 after removing a part of the hoof wall, surgically or 

 otherwise, is explained as a cell proliferation of the 

 germinal epithelium. If the human nail is removed 

 this germinal epithelium is torn, but enough remains 

 to proliferate epithelial cells in a few days which cor- 

 nify to form a thin provisional nail analogous to the 

 provisional hoof in a like injury to the horse's foot. 



THE GLANDS OF THE SKIN. 



Sweat glands are coiled simple tubular glands dis- 

 tributed over the whole surface of the skin, with the 

 exception of the inner surface of the prepuce, the 

 glans penis, and the red borders of the lips. In the 

 axilla and around the anal opening they are excep- 

 tionally large and often branched. They are most 

 numerous on the palm of the hand and the sole of 

 the foot, where they number two thousand seven 

 hundred to the square inch. On the forehead there 

 are one thousand two hundred, and on the cheek 

 about five hundred to the square inch, while over the 

 back they are the least numerous. Their total num- 

 ber over the whole body has been estimated at nearly 

 two million four hundred thousand, which, with an 



