THE BRAIN OF MAN". 417 



interosseus of the middle digit. The result of the last-men- 

 tioned arrangement is that the second digit of the pes has 

 two " dorsal " interossei, like the third digit of the manus. In 

 the Apes the interossei of the second digit are generally ar- 

 ranged in the same way in both manus and pes. 



The tendons of the flexor hallucis longiis and flexor dlgi- 

 tortim perforans are usually more closely connected in the 

 sole of the foot in Man, than in the Antliropomorplia. But 

 it is to be noted that all the apparently distinctive peculiari- 

 ties of the myology of the Antliroponiorjiha are to be met 

 with, occasionally, as varieties in Man. 



In the brain of Man, the only distinctive features, apart 

 fi'om its absolute size (55 to 115 cubic inches), are the filling 

 up of the occipito-temporal fissure ; the greater complexity 

 and less symmetry of the other sulci and gyri ; the less exca- 

 vation of the orbital face of the frontal lobe ; and the larger 

 size of the cerebral hemispheres, as compared with the cere- 

 bellum and the cerebral nerves. 



There is no diastema, though the summits of the canines 

 project, slightly, beyond the level of the other teeth. The 

 premolars have not more than two roots, and the anterior edge 

 of the crown of the anterior lower premolar is not prolonged 

 and sharp. The permanent canine tooth emerges before the 

 second molar. 



The penis is devoid of a bone (though a prismatic carti- 

 laginous body has occasionally been found in the centre of the 

 glans), and its glans has a diiferent shape from that of any of 

 the Anthroporiiorpha, The vulva looks downward and for- 

 ward, and the clitoris is comparatively small. 



The changes in the proportions of the different parts of the 

 body, at different periods of intra- and extra-uterine life, are 

 very remarkable. In a foetus an inch and a half long, from the 

 vertex to the heel, the head takes up from one-third to one- 

 fourth of the entire length. The arms and legs are of about 

 the same length, and are shorter than the spine. The forearm 

 is about as long as the upper arm, and the leg as the thigh. 

 The manus and pes are very similar in size and form ; and 

 neither pollex, nor hallux, are so different from the other digits 

 as at later periods. In a fcetus rather more than five inches 

 high, the head occupies a fourth of the entire height ; the 

 arms are longer than the spine by one-sixth of their whole 

 length, and are a little longer than the legs. The forearm is 

 about as long as the upper arm, and the thigh is a little longer 

 than the leg. The manus and pes are about equal in length. 



