XIII PHYLUM CHORD ATA 447 



eyes, and on the snout. Behind the eyes and a little nearer the 

 summit of the head, are a pair of very long flexible and movable 

 external ears or pinnce. These are somewhat spout-shaped, expand- 

 ing distally, and are usually placed vertically with the concavity 

 directed laterally and somewhat forwards, leading to the external 

 auditory opening. The tuch is a distinct constriction, but rela- 

 tively short as compared with the neck of the Pigeon. The trunk 

 is distinguishable into thorax in front and abdomen behind. On 

 the ventral surface of the abdomen in the female are four or five 

 pairs of little papillae — the teats. At its posterior end, below the 

 root of the tail, is the anal opening, and in front of this in the 

 male is the penis, with a small terminal urinogenital aperture, and 

 with the testes, each in a prominent scrotal sac, at the sides : and 

 in the female the opening of the vulva. In the space {perinceum) 

 between anus and penis or vulva are two bare, depressed areas of 

 skin into which open the ducts of certain glands — the perinmal 

 glands — with a secretion having a strong and characteristic odour. 

 The tail is very short and covered with a tuft of fluffy fur. 



The fore- and hind-limbs, both of which take part in locomotion 

 and in supporting the weight of the animal, differ considerably in 

 size — the fore-limbs being much shorter than the hind -limbs. 

 Both have the same general divisions as in the Lizard. The 

 upper arm is almost completely hidden by the skin being applied 

 closely against the side of the body. The manus is provided with 

 five digits, each terminating in a horny claw. The thigh is also 

 almost hidden by the skin ; the pes has four digits only, all pro- 

 vided with claws. 



Skeleton. — The spinal column of the Rabbit is divisible, like 

 that of the Pigeon and the Lizard, into five regions — the cervical, 

 the thoraciCj the lumbar, the sacral, and the caudal. In the cervical 

 region there are seven vertebrae ; in the thoracic twelve or some- 

 times thirteen, in the lumbar seven, or sometimes six, in the sacral 

 four, and in the caudal about fifteen. 



The centra, of the vertebrae in a young Rabbit consist of three 

 parts — a middle part which is the thickest, and two thin discs of 

 bone — the epiphyses — anterior and posterior, applied respectively 

 to the anterior and posterior faces of the middle part or centrum 

 proper. Between successive centra in an unmacerated skeleton 

 are thin disc-like plates of fibro-cartilage — the inter-vertebral discs. 

 The transverse processes of all the cervical vertebrae, except the 

 seventh or last, are perforated by a canal, the vertebrarterial canal, 

 for the passage of the vertebral artery. The first vertebra or atlas 

 (Fig. 1081, A) resembles the corresponding vertebra of the Pigeon 

 in being of the shape of a ring without any solid centrum like that 

 of the rest. On the anterior face of its lateral portions are two 

 concave articular surfaces for the two condyles of the skull. The 

 second vertebra or axis {A and B) bears on the anterior face of its 



