84 ANIMAL BIOLOGY. [Parti. 



corpuscles with their concentric coats. The tissue to the right of 

 the oval corpuscle in iii. is fatty tissue, above which is the cut 

 end of a blood-vessel. 



Passing down through the epidermis into the dermis are 

 spiral tubes, each ending in a coiled glandular knot. These are 

 the sweat glands. One of these is shown in iii., while portions 

 of three other glandular knots are cut in different planes. 



Imbedded in the mammalian skin are the hairs characteristic 

 of the order. Each hair is moulded on a little papilla of the 

 dermis (iv. ) Around the root of the hair is a root-sheath com- 

 posed of an internal and an external layer continuous with the 

 deeper and superficial layers of the epidermis respectively. Out- 

 side this is a fibrous dermic layer, passing up into the papilla. 

 The whole is in iv. (from the scalp of a negro) imbedded in 

 fatty tissue. The whole tubular depression in the skin contain- 

 ing the hair is called the hair follicle. Into it there open, near 

 its external end, sebaceous glands, secreting an oily substance. 

 The position of one of these is roughly indicated in 30, v. 



Fig. 30, vi. and vii. show rabbit's hairs under a fairly high 

 power. Fig. 30, vi. is from near the point of a white hair, and 

 shows the imbricating scales of the cuticle. Fig. 30, vii. shows, 

 besides these scales, the fibrous cortex and the internal irregular 

 pigmented or air-containing medulla. In each case the proximal 

 or root end of the hair is uppermost. 



In the nails or claws the external epidermic scales become 

 specially soldered together, and horny or fibrous in consistency. 

 They are moulded in the rabbit on large papillae, their roots 

 being also covered over with a fold of skin so as to lie in a 

 groove. 



Attention may here be drawn to the different kinds of glands 

 Avith which we have become acquainted in the skin and else- 

 where. 



1. Simple tube-like depressions, e.g. peptic glands. 



2. Simple flask-shaped depressions, e.g. cutaneous glands of 



frog. 



3. Tubes coiled at the end. Sweat glands. 



4. Tubes with simple branches. Sebaceous glands. 



