786 



PHYLUM CHORDATA : CLASS MAMMALIA 



acteristic odour. In front of the anus is the urinogenital 

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

 in the female a sHt 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. 



Fig. 469. — Atlas vertebra of a Mammal, side view. — From a 



Specimen. 



A., Anterior end; P., posterior end; T.P., large transverse 

 process ; N., median dorsal line with only a hint of a 

 neural spine ; C, deep concavity for one of the two con- 

 dyles of the skull. 



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 

 hare ; it forms the blubber of whales. Beneath the skin 

 is a thin sheet of muscle (the panniculus carnosus), by 

 means of which the skin can be twitched, as in horses, 

 etc., and when this is removed with the skin, many of the 



