14 



ANATOMY OF THE RABBIT 



which is known as the epidermis, or scarf-skin, is stratified, the 

 deepest cells being columnar, formative, growing units which pro- 

 duce daughter cells that are gradually pushed outward and in- 

 creasingly flattened so that those at the surface are squamous 

 and are successively discarded. The several 

 layers combined produce but a thin mem- 

 brane. It extends over the entire surface 

 of the body and connects at certain points 

 with the epithelia of the internal surfaces. 

 It is supported by a thick resistant layer 

 of connective tissue which forms the true 

 skin or corium. Between the epithelium 

 and the underlying connective tissue there 

 is usually a distinct basement membrane, 

 derived from the inter-cellular substance 

 of the connective tissue. 



In the greater portion of the alimen- 

 tary tract the lining epithelial layer is sim- 

 ple or one-layered and is associated with 

 a thin layer of smooth muscle to form a 



From a section of HIUCOUS tuniC (Fig. 15, t.mS.). The CClls 



ow rl^i:%:'erJ:ri7s. ^re columuar and have on their free sur- 



ttsle°'oftriu';;re;e7d?rm^! ^^^^^ ^ ^^"^ ^^ modified protoplasm, the 

 f hair follicle; g sebaceous striated bordcr, which is important in ab- 



gland; p, papilla; s, hair shaft. ' '^ 



sorption. 



The free surfaces of the epithelial cells sometimes have delicate, 

 hair-like outgrowths, which may be non-motile (brush border, as 

 in the proximal convoluted tubules of the kidneys) or motile (cilia, 

 as in the uterine tubes, respiratory passages, etc.). 



Among secondary products of epithelial origin is the coating of 

 hairs on the surface of the body, the presence of which is a strictly 

 characteristic mammalian feature. It is a protective investment 

 arising from the epidermis. Each hair is produced by the modifi- 

 cation of the central portion of an ingrowth of the epidermis, termed 

 the hair follicle (Fig. 2, f). The latter contains at its base a small 

 elevation of the underlying vascular connective tissue, the hair 

 papilla, through which the structure is nourished. On the general 

 surface of the body of the rabbit the hair follicles are arranged in 



Fig. 2. 



