SKIN AND MUSCLES. 699 



by the habitual winking of the upper eyelid, The nostrils 

 are two slits at the end of the snout, and are connected 

 with the mouth by a " hare-lip " cleft in the middle of the 

 upper lip. In front of the mouth are seen the chisel-edged 

 incisors, a pair on the mandibles, and two pairs on the pre- 

 maxillae the smaller pair hidden behind the larger pair. 

 The first milk incisors above and below never cut the gum, 

 but are absorbed before birth ; the second milk incisors 

 above (there are none below) are functional, but are shed 

 about the third week of extra-uterine life ; the same is true 

 of the milk premolars. Into the toothless gap or diastema 

 between the front and back teeth the hairy skin of the lips 

 projects into the mouth. This generally occurs in Rodents, 

 and is said to prevent the inedible substances which they 

 gnaw from passing backwards to the gullet. On the sides 

 of the snout, and about the eyes, there are tactile hairs or 

 vibrissae. 



The plump trunk is separated from the head by a short 

 neck. The tail is very short, but in the scampering wild 

 rabbit it is conspicuous as a white tuft, which some 

 naturalists interpret as a directive signal. Beneath the base 

 of the tail the food canal ends, and beside the anus are the 

 openings of the perineal glands, whose secretion has a char- 

 acteristic odour. In front of the anus is the urogenital 

 aperture, in the male at the end of an ensheathed penis, 

 in the female a slit or vulva, with an anterior process or 

 clitoris the homologue of the penis. Beside the penis in 

 the male lie the scrotal sacs, into which the testes descend 

 when the rabbit becomes sexually mature. Along the 

 ventral surface of the thorax and abdomen in the female 

 there are four or five pairs of small teats or mammae. 



The limbs have clawed digits, five on the fore-feet, four 

 on the hind-feet ; they are very hairy. 



Skin and muscles. The skin is thickly covered with 

 hair, and has the usual sebaceous and sudorific glands, 

 besides special glands, such as the perineal glands beside 

 the anus, the glands of the eyelids, the lachrymal glands, 

 and the mammary glands developed in the females. 

 Between the skin and the subjacent muscles there is a 

 layer of fatty tissue, known as the panniculus adiposus ; it 

 is usually present in Mammals, but absent in the common 



