STRUCTURE OF THE TEETH. 



29 



are inserted somewhat obliquely as in the 

 prognathous races of man, are broad and 

 chisel-shaped, and have single roots. The 

 canines are conical, sometimes curved and 

 vi^ith sharp edges; the premolars w^ith blunt 

 tubercles; the molars four-sided, with at least 

 four blunt tubercles separated by a trans- 

 verse furrow, and sometimes in addition a 

 fifth posterior unpaired tubercle. The dif- 

 ferences are due to greater or less variations 

 in the relative size of the individual teeth, as 

 well as in the structure of the different parts; 

 in particular to the exceptional development 

 ot the canines and the somewhat sharper 

 cusps of the premolars in the baboons, to the 

 more pointed form assumed by the molar 

 tubercles in the Arctopitheci, which feed 

 chiefly on insects. The range of these varia- 

 tions is, however, only very small, and one 

 may say in general, that the dentition of the 

 Simize, like that of man, exhibits a somewhat 

 indifferent character, but is most closely 

 allied to that of the tuberculate group of the 

 Ungulata, more especially that of many fossil 

 genera of this group, yet with indications of 

 an approximation to the insectivorous type 

 of dentition on the one side, and to that of 

 the carnivores on the other. 



With respect to the structure of the vertebral 

 column, the chest, the shoulder-girdle, and 

 the pelvis, we only observe, without desiring 

 to go into too great detail, that a wide cleft 

 can be shown to exist between the anthropoid 

 apes, which nearly approach the human struc- 

 ture adapted for an upright position, and the 

 other Simiae, in which the arrangement of 

 parts characteristic of four-footed mammals 

 larevails, although with a gradual approach to 

 the type of the anthropoid apes. The verte- 

 bral column shows only approximations to 

 that double S-shaped curve, which is so char- 

 acteristic of man, and which in an upright posi- 

 tion distributes the weight of the body over 

 a greater area. The chest in the terrestrial 

 monkeys as in other four-footed mammals is 

 laterally compressed, and the sternum projects 



to a certain extent in a wedge-form in the 

 middle line; and only gradually is the broad 

 flattened form of chest such as is seen in the 

 anthropoid apes and in man developed. The 

 shoulder-girdle is always composed of a broad 

 scapula or shoulder-blade and a powerful 

 collar bone, such as is met with in all 

 mammals in which the fore-limbs serve not 

 only to support the body, but also to perform 

 other functions, such as digging, flying, swim- 

 ming, grasping, and so forth. The pelvis, 

 which is narrow and placed parallel to the 

 vertebral column in the lowest Simise, becomes 

 gradually broader and more basin-shaped, and 

 in the anthropoid apes closely approaches in 

 structure the human pelvis, which, in conse- 

 quence ot the upright position, has to support 

 the whole weight of the abdominal viscera. 



We now turn to the limbs, which indeed 

 are constructed entirely on the human type, 

 but yet exhibit many differences. First of all 

 it may be observed that the fore-limbs are in 

 every case longer and more muscular relatively 

 to the hind ones than in man, who has com- 

 paratively the strongest and longest legs of 

 all animals, as is only natural when we consider 

 that in him the upright position is normal, and 

 the legs consequently have to bear the whole 

 weight of the body. The relative proportions 

 of the two pairs of limbs exhibit a gradual 

 diminution in the amount of difference. From 

 the monstrously long arms of the gibbons and 

 the spider-monkeys a continuous process of 

 shortening can be observed, especially in the 

 anthropoid apes, until we come to man; yet 

 even the arms of the gorilla, the ape that 

 in this respect approaches most nearly to 

 man, are still considerably longer than in 

 the human species. The shorter legs of the 

 Simla; are less muscular; the thighs are flat, 

 the buttocks angular, and there are no calves. 

 But the number and relations of the bones are 

 the same as in man, and moreover the Simiae 

 have the same power of pronation in the fore- 

 arm as man, though not so highly developed. 



The digits require a more thorough con- 



