OJF T1IE CLASS MAMMALIA. 33 



The structural modifications iu the genus Homo, — the sole re- 

 presentative of the Archencephala, — more especially of the lower 

 limb, by which the erect stature and bipedal gait are maintained, 

 are such as to claim for Man ordinal distinction on merely external 

 zoological characters. But as I have already argued, his psycho- 

 logical powers, in association with his extraordinarily developed 

 brain, entitle the group which he represents to equivalent rank 

 with the other primary divisions of the class Mammalia founded 

 on cerebral characters. In this primary group Man forms but 

 one genus, Homo, and that genus but one order, called Bimana, 

 on account of the opposable thumb being restricted to the upper 

 pair of limbs. The testes are scrotal ; their serous sac does not 

 communicate with the abdomen ; they are associated with vesi- 

 cular and prostatic glands. The penis is pendulous, and the pre- 

 puce has a fraenum. The mammae are pectoral. The placenta is 

 a single, subcircular, cellulo-vascular, discoid body. 



Man has only a partial covering of hair, which is not merely 

 protective of the head, but is ornamental and distinctive of sex. 

 The dentition of the genus Homo is reduced to thirty-two teeth 

 by the suppression of the outer incisor and the first two pre- 

 molars of the typical series on each side of both jaws, the dental 

 formula being : — 



]— l 2—2 3—3 qo 



All the teeth are of equal length, and there is no break in the 

 series ; they are subservient in Man not only to alimentation, but 

 to beauty and to speech. 



The human foot is broad, plantigrade, with the sole, not inverted 

 as in Quadrumana, but applied flat to the ground ; the leg bears 

 vertically on the foot ; the heel is expanded beneath ; the toes are 

 short, but with the innermost longer and much larger than the 

 rest, forming a ' hallux ' or great toe, which is placed on the same 

 line with, and cannot be opposed to, the other toes ; the pelvis is 

 short, broad, and wide, keeping well apart the thighs ; and the 

 neck of the femur is long, and forms an open angle with the shaft, 

 increasing the basis of support for the trunk. The whole verte- 

 bral column, with its slight alternate curves, and the well-poised, 

 short, but capacious subglobular skull, are in like harmony with 

 the requirements of the erect position. The widely-separated 

 shoulders, with broad scapulas and complete clavicles, give a 

 favourable position to the upper limbs, now liberated from the 

 service of locomotion, with complex joints for rotatory as well as 



LINN. PROC. — ZOOLOGY. 3 



