22 THE CAT. [CHAP. n. 



the colouring matter of the skin, and are often considered as forming 

 a distinct part called the rete mucosum. The superficial or older 

 layers acquire a horny nature. The surface of the epidermis ex- 

 hibits numerous minute orifices of sweat-glands the pores and, 

 especially on the paws, numerous minute ridges. 



11. The DERMIS, or coriitm, is a form of connective tissue. Its 

 upper surface is almost free from fibres, but beneath, these first grow 

 abundant and then begin to leave larger and larger interspaces, till 

 the fibrous tissue becomes what is called " areolar" and so forms the 

 substance connecting the skin with the subjacent structures, i.e., it 

 forms that white, filmy substance which is broken through when the 

 animal is skinned. In the deeper portion of the true skin there are 

 curled yellow fibres of elastic tissue, and there may be some or many 

 muscular fibres. Its outer surface is drawn out into little promi- 

 nences or papillae arranged in close-set parallel rows (especially on 

 the paws), which occasion, the ridges above mentioned, or existing in 

 the superimposed epidermis. Many of these papillae contain nerves 

 and blood-vessels, the former ending in a fine coil about a minute 

 ball or core of nucleated tissue, thus forming what are called " axile 

 bodies," or "touch corpuscles" (Fig. 7, B). 



Sweat-glands consist of minute tubes, each opening at the surface 

 at a " pore," whence it descends into the skin and passes through it 

 into the loose connective or areolar tissue beneath it, where it ends 

 in a coil surrounded by minute blood-vessels. The meshes of the 

 loose subcutaneous tissue contain fat, which, as before mentioned, is 

 enclosed in minute bags of membrane. It is fluid during the life of 

 the animal, and both helps to keep the body warm (being a bad 

 conductor of heat) and serves as a store of nutriment. Other 

 structures called Pacinian bodies are found in some parts of the skin 

 of the body notably in a membrane (the mesentery) which invests 

 part of the bowels. Each such body consists of a number of layers 

 of membrane, with fluid interposed, and with a central space into 

 which a nerve enters (Fig. 7, A). 



12. The CLAWS, of which there are five to each fore-paw, and four 

 to each hind-paw, are special thickenings of epidermis, and are 

 (like the outer layer of epidermis generally) horny. But the dermis 

 is also specially modified with a view to the formation of the claws ; 

 for at the root of each claw it forms a transverse crescentic fold over it, 

 while beneath the claw, it is produced into a number of close-set rows 

 of papillae richly supplied with blood-vessels forming what is called 

 the matrix of the claw. From its surface, and also within the 

 crescentic fold, fresh epidermal cells are continually formed, which 

 rapidly become harder, and cohere to form the claw, the root part 

 of which is soft, like the deeper layer of epidermis, with which 

 layer it is directly continuous. The claws are placed around the 

 terminal part of the last bone of each toe, completely investing it, 

 and ending in a sharp point. 



13. The HAIRS each consist of a root, fixed in the skin, and the 

 shaft, or stem, which may be cylindrical, or flattened. Each hair is 



