CHAP. ii. ANATOMY OF OX, SHEEP, AND PIG. 413 



confined to the right diaphragmatic region, the gall-bladder being 

 attached near its superior extremity. 



The thorax is not so long as, and is less capacious than, in the horse. 

 The lungs are noteworthy for the distinctness with which their lobules 

 are defined, being separated by thick layers of tissue continuous with 

 the pleura which covers the lungs. This accounts for the special 

 character of the lesions accompanying pleuro-pneumonia in the ox. 



THE SHEEP. This animal resembles the ox in most of the essential 

 characters. The lips, however, are thin, very mobile, and prehensile. 

 The upper lip has no muffle, but is covered with hair, and is divided 

 by a median groove or fissure. The mucous membrane lining the 

 interior of the mouth is often spotted black. Like the ox, the sheep 

 is a true ruminant, and it has the same kind of stomach as the ox. 



THE PIG. Of the domesticated animals this possesses the shortest, 

 widest, and strongest cervical vertebra. The skull has a pronounced 

 occipital crest. At the free extremity of the median bone of the 

 nose, a small floating bone, the pre-nasal ossicle or scooping bone, 

 strengthens the cartilaginous snout. The rostrum suis, or snout, is a 

 tactile organ employed to dig the ground, and is covered by a dark- 

 coloured skin kept moist by a secretion. The articulation of the man- 

 dible is such that the jaw moves freely in all directions. The sternum 

 is broad, like that of the ox. The second, third, fourth, and fifth 

 metacarpals are all distinct, but the second and fifth digits do not reach 

 the ground. 



In the mouth, the lips are widely cleft, the lower being pointed and 

 but little developed. The upper lip is confounded with the snout, and 

 the cheeks are small and thin. Where the gullet enters the stomach, 

 a groove extends in the direction of the exit from that organ. As this 

 groove is well developed in ruminants, we have here a foreshadowing of 

 the true ruminant stomach. The pig's stomach is less curved on itself 

 than that of the horse, but, like the latter, it exhibits an internal 

 differentiation into a functionless and a functional portion. Its capacity 

 is from 1 J to 2 gallons. 



The small intestine is about 56 feet long ; the large intestine 16 feet. 

 The liver has three well-marked lobes, the middle one supporting the 

 gall-bladder. The urinary bladder is thin, and of considerable capacity 

 as in ruminants. 



DENTITION. In the dentition, or tooth-furniture, of mammals there 

 are two sets of teeth. The earlier set fall away in succession, and are 

 gradually replaced by a later set, which come into place once for all. 

 Hence, the former set constitute the temporary dentition, or, as they 

 mostly appear when the animals are still sucking, the milk dentition. 

 The later set constitute the permanent dentition. Every reader can 

 recall the days of childhood, when the teeth became "loose," and, after 

 being pulled out, were replaced by new ones. This, however, happens 

 only once for each tooth concerned, and the anxious question sometimes 



