EXTERNAL CHARACTERS 297 



4. The vibrissse or whiskers are long, stiff, tactile hairs, at 



the sides of the snout, and above and below the eyes. 



5. The external ears or pinnae are of great size and freely 



movable. Each is folded longitudinally, and is sup- 

 ported by cartilage at its base, where it surrounds 

 the external auditory aperture. 



B. The Trunk. 



This is divided into an anterior portion or thorax, supported 

 laterally by the ribs ; and a posterior part or abdomen. 



Feel through the skin, and determine the position of the 

 vertebral column and ribs. 



1. The anus is a small median aperture beneath the base of 



the tail. 



2. The perinaeal pouches are a pair of hairless depressions 



of the skin, in front of and at the sides of the anus: 

 into them open the ducts of the perinaeal glands, 

 the secretion of which has the strong smell charac- 

 teristic of the rabbit. 



3. The urino-genital aperture is situated in both sexes just 



in front of the anus. 



a. In the male the aperture is placed at the end of the 



long conical penis, which can be retracted within 

 a loose sheath of skin, the prepuce. 



b, In the female the opening, or vulva, is slit-like and 



larger than in the male ; and its anterior margin 

 is produced into a small fleshy process, the 

 clitoris, which corresponds to the penis in the 

 male. 



4. [The scrotal sacs, found in the male only, are a pair of 



prominent oval pouches of skin, at the sides of the 

 penis, into which the testes descend.] 



5. [The teats or mammae of the female are four or five pairs 



of small papillae, perforated by the openings of the 

 ducts of the mammary or milk-glands. They are 

 arranged at intervals along the ventral surface of 

 the thorax and abdomen ; the most anterior pair 



