GENERAL CHARACTERISTICS. 



63 



transposition of the weapons of attack and 

 defence. The incisors, which stand vertically 

 in the upper jaw but are almost horizontal in 

 the lower, gradually disappear altogether in 

 the former. While the pigs have in all six 

 incisors in the upper jaw, the hippopotamuses 

 have only four, the camels only two, and in 

 all other ruminants they are altogether absent. 

 On the other hand, the lower incisors in the 

 latter are increased by a pair, so that their 

 total number is brought up to eight. It is 

 probable indeed that the outermost pair con- 

 sist of canines which have got displaced for- 

 wards. The canines, which in the hippopo- 

 tamuses, pigs, musk-deer, and chevrotains 

 are formidable weapons, always more highly 

 developed in the male than in the female, are 

 reduced in size in the camels and most of the 

 deer family, and disappear entirely in the 

 other ruminants. It cannot, however, be 

 said that the growth of horns is an equivalent 

 for the loss of the canines, for the muntjac 

 has both horns and large canines, which are 

 used by it as weapons. The number of 

 the cheek-teeth, which are separated by an 

 interval from the front-teeth, and can often 

 be distinguished by their external form as 

 molars and premolars, diminishes through the 

 loss of the latter. The last molar exhibits a 

 manifest tendency to increase in size, and 

 this tendency is so marked in the wart-hogs 

 that the masticating surface in them belongs 

 wholly to this single enormously enlarged 

 molar. 



There is little to say regarding the internal 

 organization. The brain and the skull are 

 always very small in relation to the size of the 

 body and the development of the elongated 

 jaws. The brain itself exhibits a peculiar 

 system of convolutions, which, in the smaller 

 forms, are more simple, in the larger more 

 complex. The cerebral hemispheres never 

 cover the cerebellum, and they even leave a 

 portion of the mid-brain exposed. More- 

 over, the Artiodactyla in general stand upon 

 a very low level of intelligence, which, how- 



ever, does not prevent them from having a 

 certain keenness of sense. 



Among the anatomical features we would 

 draw attention also to the tendency of the 

 stomach to become subdivided, a tendency 

 which goes hand in hand with the change 

 from a miscellaneous to a purely vegetable 

 diet. In the Perissodactyla this change of 

 habits affected chiefly the colon and caecum. 

 Most of the pigs still have a simple stomach. 

 In the hippopotamuses and peccaries that 

 portion of the stomach into which the oeso- 

 phagus or gullet opens, the so-called cardiac 

 end, is divided into two, making three parts 

 in all. This threefold division is maintained 

 likewise in the chevrotains; but in the other 

 ruminants the other end of the stomach, the 

 pyloric end, is also divided into two parts, 

 so that the stomach now consists of four dif- 

 ferent sacs, which have four distinct functions. 



Only in the pigs are the teats found ex- 

 tending in pairs along the whole length of the 

 abdomen. In the other Artiodactyla they are 

 situated in the region of the groin (placed in- 

 guinally). The placenta is always diffuse, 

 spread over the whole surface of the ovum; 

 but while in the pigs, camels, and chevrotains 

 the placenta has still preserved a primitive 

 character, being composed of delicate isolated 

 tufts, these form in the other ruminants more 

 compact masses, which have been called coty- 

 ledons. 



Almost all Artiodactyla live socially, often 

 in numberless herds, which, however, are 

 without that more or less intelligent organ- 

 ization observable in troops of horses or 

 societies of monkeys. Some rely for their 

 safety on their strength, others on their 

 speed. Although these animals are mostly 

 stupid and unintelligent, yet certain of their 

 senses, as smelling and hearing, may be 

 extraordinarily keen and delicate. They can 

 scarcely be said to show any attachment to 

 man, who, nevertheless, has domesticated a 

 great number of them. In all, without ex- 

 ception, even in the most peaceably disposed. 



