THE ANATOMY OF THE RABBIT. 371 



and dilated like the prove nficuhis of a bird. And, in Arvicola, 

 the stomach becomes deeply constricted, and a groove leads 

 from, the oesophagus toward the pyloric end, reminding one 

 of certain Artiodactyla. 



In some few genera, the ureters open into the fundus of 

 the bladder, or near it. 



Although the genera and species of the Rodetitia are 

 more numerous than those of any other mammalian order; 

 aud although they are adapted to very different modes of life — 

 some, like the " Flying Squirrels," floating through the air by 

 means of a parachute-like expansion of the integument be- 

 tween the fore- and hind-limbs ; others being arboreal, like the 

 ordinary Squirrels ; or among the swiftest of runners, as the 

 Hares ; or strong burrowers, as the mole-like Sathyeryus ; 

 or aquatic, like the Water-vole — their structural differences 

 are comparatively insignificant, and the subdivision of the 

 order into large groups is proportionately difficult. 



Brandt has divided the Rodents according to their cranial 

 characters into Soiuromorpha, Myomorpha, Systricomorpha, 

 and Lagomorpha ; or, Squirrels, Rats, Porcupines, and Conies, 

 if we use these English names in a broad and tribal sense. 



The student will find the Rabbit, one of the Lagomorpha, 

 to be a conveniently-sized and easily-obtained subject for study. 

 The following are the most important points to be noted in 

 its structure : The hairy covering of the body extends over 

 the palmar and plantar regions of the feet, and into the interior 

 of the mouth, so that there is a band of hair on the inside of 

 each cheek. There are five digits on the fore-foot, or manus ; 

 but the pollex is smaller than the others. The pes has only 

 four digits, and the hind-limb is longer than the fore-limb. 

 The upper lip is large, flexible, and cleft in the middle line ; 

 the large eyes are provided with a third eyelid, and the pinnae 

 of the ears are very long and mobile. The tail is short and 

 recurved. The male has a recurved penis, and on each side 

 of it a scrotal sac. The female has five pair of abdominal teats. 

 In both sexes perineal glands are present, consisting of a 

 saccular involution of the integument with rugose walls, into 

 which the duct of a special gland lodged at the side of the 

 penis, or of the clitoris, opens. 



There are nineteen dorso-lumbar vertebrae, of which twelve 

 are dorsal. Of the four sacral vertebrae only the first unites 

 with the ilia. The dorsal vertebrae have well-developed spinous 

 and transverse processes. At about the eighth, a mammillary 

 ^locess, or metapophy sis, becomes obvious ; and in the succeed' 



