xxix. 4 ELEPHANT CHARACTERS 713 



upper segments and no great extension of the lower. The ulna and 

 fibula are complete and bear part of the weight, the ulna and radius 

 being held permanently crossed in a fixed position of pronation. 

 Walking is of a modified digitigrade type; all three of the short 

 phalanges of each digit reach the ground, but the greater part of the 

 weight is taken by a pad of elastic tissue at the back of the foot. 

 There are five digits in each foot, united by a web to make a firm basis, 

 and having small, flat, somewhat hoof-like nails at the tips. The ribs 

 carry so much weight that respiration is almost wholly diaphragmatic 

 and the lungs are fused to the walls of the thoracic cavity by elastic 

 tissue. 



The soft parts of elephants show some features retained unmodified 

 from their early ungulate ancestry. Thus the cerebral hemispheres 

 are relatively rather small and leave the cerebellum uncovered. In 

 other respects the brain is well developed, it has a greater absolute 

 size than that of any other land mammal (6,700 cm 3 ). The proverbial 

 intelligence and memory capacity have been verified by experiment. 

 Smell, hearing, and the tactile organs of the trunk provide the main 

 receptors, vision being less developed. Like many other animals with 

 large brains there is a long period of post-natal growth and life is social. 

 Much information is no doubt learned from other individuals, and 

 it has been shown that elephants can learn to discriminate between 

 upwards of 100 pairs of visual situations. 



In spite of the specialization of the head for a herbivorous diet, the 

 stomach and intestine remain simple and there is no special large 

 fermentative chamber, though the caecum is long and sacculated and 

 there is an ileocaecal sphincter. 



The testes are remarkable in that, as in other paenungulates, they 

 lie close to the kidneys, and have made no movement of descent into 

 a scrotum. The two horns of the uterus remain separate, though united 

 externally. Only one young is born at a time, after a gestation of 

 twenty-two months. The placenta has a superficial similarity to the 

 zonary arrangement of carnivores, but in structure resembles that of 

 hyraxes and sirenians. At the poles are areas of diffuse, non-deciduate 

 placenta while in an annular zone round the middle there is much 

 invasion of the trophoblast, the details of which are not known. 

 Development is slow and Asian elephants reach puberty at about 13- 

 14 years, African elephants rather earlier. 



The earliest-known member of the elephant line, * Moeritherium, 

 from the Upper Eocene of Egypt, was only 2 ft high and was probably 

 partly aquatic, with eyes and ears placed high, as in the hippopotamus. 



