24 THE CAT. [CHAP, n] 



The root, or bulb, of each hair consists of the dermal sac with its 

 enclosed papilla and the epidermal formation which lines the sac 

 and invests the papilla. It is considerably larger than the diameter 

 of the hair it deyelopes. 



The cat's whiskers are simply hairs of great size, the bulbs of 

 which are well furnished with blood-vessels and nerves. 



Hairs are inserted obliquely into the skin, but can be made to 

 stand up, or "on end" as notably on the cat's tail when the 

 animal is enraged by means of the contraction of small muscular 

 fibres which pass from the skin to the hair-bulbs. 



Fig. 8. TRANSVERSE SECTION OF A CAT'S WHISKER, GREATLY MAGNIFIED. 

 e. Cortical substance. | in. Pith or medulla. 



Certain accessory structures are called sebaceous (/kinds. These 

 are minute flask-shaped bags (secreting an oily substance), which 

 open into the upper part of the hair follicles, and so serve to 

 lubricate the hair. 



New hairs are formed by the budding off of a new papilla and 

 follicle from beside those first developed, and by the growth of a 

 cluster of epidermic cells at the bottom of the new follicle. Neither 

 the new nor the older follicles are really formed by an actual in- 

 flection of the skin, though when completed they appear as if they 

 had been so formed. Minute blood-vessels and nerves enter the roots 

 of hairs, but do not extend beyond the dermal papilla. 



14. Such are the appendages and such is the nature of the skin 

 which clothes the cat's body externally, and which varies in thickness 

 in different regions, being very thin on the lips, ears, and eyelids, 

 thicker on the back and outer sides of the limbs than on the belly, 

 and especially thick upon the pads of the feet on which the animal 

 walks. Of these there are seven in the fore paw, and five in the 



