THE INTEGUMENTAEY APPENDAGES. 



795 



Fig. 368. 

 d 



derma (or corium), and forming an elliptical glomerule, generally lying 

 obliquely to the surface of the skin in the Horse. The excretory canal is 

 detached from this glomerule, and passes 

 through the derma and epidermis in a spiral 

 manner. 



The blood-vessels form a very rich network 

 in the papillary layer of the derma, and also 

 surround the sebaceous and sudoriparous 

 glands. The lymphatics are disposed like the 

 capillaries. 



The nerves are arranged in two layers : 

 one loosely distributed in the corium -, the 

 other is very close, and is lodged in the papil- 

 lary layer of the derma, which is traversed 

 by recurrent fibres giving off tubes that pass 

 into the nervous corpuscles of the papillae. 



Fig. 367. 



MAGNIFIED 



VERTICAL SECTION OF THE SKIN TREATED WITH A 



SOLUTION OF CAUSTIC SODA, showing the branches of 

 cutaneous nerves, a, 6, inosculating to form a terminal 

 plexus, of which the ultimate ramifications pass into 

 the papillae, c, c, c, 



EPIDERMIS. The epidermis is a thin pel- 

 licle, covering the superficial face of the 

 derma ; it is destitute of nerves and blood- 

 vessels, and is formed of cells which are 

 being continually deposited on the corium ; s 

 these cells become flattened in layers as they 

 are pushed up from the latter, and are des- 

 troyed by friction on the surface of the skin. 

 The deep face of the epidermis is moulded 

 on the upper surface of the derma; con- 

 sequently, it lodges the papillas, and dips into 

 the follicles and excretory ducts of the glands 

 of the skin ; its external face is not a very 

 exact repetition of the surface of the derma, and is covered with hair. The 

 epidermis tends to equalise, and to fill up, the depressions existing between 

 the papillae. 



a, Contorted tubes composing the 

 gland, and uniting in two ex- 

 cretory ducts, 6, 6, which join 

 into one spiral canal that per- 

 forates the epidermis at c, and 

 opens on its surface at d\ the 

 gland is imbedded in fat vesi- 

 cles, e, e~ 



