14 ANIMAL BIOLOGY. [Parti. 



passages, which open from the organ of Jacobson into the mouth 

 a little behind the incisors. There are also small Eustachian tubes 

 leading to the cavity of the drum of the ear. At the back the 

 mouth communicates (1) with the lungs by the glottis, (2) with 

 the stomach by the oesophagus. The tongue is fixed behind and 

 free anteriorly. At its sides are oval wrinkled patches (papillce 

 foliatce), probably gustatory. 



The other median apertures are the anus, and the urino- 

 genital opening, of which the latter is anterior, and differs accord- 

 ing to sex. Of the six lateral apertures, the most anterior pair 

 are the external nares ; the second pair the ear openings, guarded 

 by the large external ears, and passing down to the tympanic 

 membrane, which is not exposed at the surface as in the frog ; 

 and the posterior pair, ducts of the perineal glands, situated on 

 hairless spaces on either side of the anus. These glands pour 

 forth an odorous secretion. In addition to these lateral 

 apertures, there are in the female those on the teats of the 

 mammary glands. 



The fore-legs are considerably shorter than the hind-legs. 

 Each is jointed to the shoulder girdle, and has a brachium, an 

 antibrachium, and a manus with five digits. The hind limb has 

 a femur, crus, and pes with four digits. Thus the great toe is 

 suppressed in the rabbit, and the thumb in the frog. The main 

 hairy cushion under the sole of each foot is the pulvmus, the 

 smaller cushion under each digit the pulvulus. The ankle is not 

 elongated as in the frog, and there is a backwardly projecting 

 heel. All the digits bear strong claws, or are unguiculate. The 

 rabbit walks on the toes of its manus, but allows the whole 

 plantar surface of the pes to touch the ground. Some animals, 

 like the cat, walk on the toes of both fore and hind feet, and are 

 called digitigmde. Others, like the bear, walk on the whole 

 surface of both manus and pes, and are called plantigrade. 



In their normal position the limbs of the rabbit lie parallel 

 with the body ; but whereas the femur runs forward from the 

 hip girdle, the brachium runs backward from the shoulder- 

 girdle. So that we must regard the fore-limb as having been 

 folded backward from the typical position (Fig. 3, B.), while the 



