418 THE ANATOMY OF VERTEBRATED ANIMALS. 



In a foetus eight and a half inches high, the head measures less 

 than a fourth of the whole height ; the arms are longer than 

 the spine by a fourth of their whole length, and they are longer 

 than the legs. Tiie extremities of the digits reach down to 

 the knee w4ien the body is erect. 



At full term, the height of the head of the human foetus 

 is rather less than a fourth that of the whole body, and the 

 legs are longer than the arms. The arm is longer than the 

 forearm and the thigh than the leg. The hands and the feet 

 are still about equal in length. 



Thus it would appear that, while the head grows more 

 slowly than the rest of the body, throughout the period of ges- 

 tation, after the embrj^o has attained more than two inches in 

 length ; the arms grow proportionally quicker than the body 

 and legs, in the middle of gestation, when the proportions 

 most nearly resemble those of the Anthropomorpha. In the 

 latter part of the period of gestation the legs gain on the arms, 

 and the proximal segments of the limbs on the distal ones. 

 After birth these changes are continued. The adult has, on 

 the average, three and a half times the height of the new-born 

 child, and his arms are elongated in the same proportion. 

 But the head is only twice as large, while the legs of the adult 

 are five times as long as those of the child. At all ages after 

 birth, the distance between the extremities of the digits of 

 the outstretched arms is equal to the height in average Eu- 

 ropeans. 



Sexual differences, independent of the genitalia, are per- 

 ceptible at birth ; and the female infant is, as a rule, slightly 

 smaller than the male. These diiferences become more marked 

 at, and subsequent to, puberty ; and are seen in the smaller 

 stature of the female, the larger size of the head in proportion 

 to the stature, the shorter thorax, the longer abdomen, and the 

 shorter legs ; so that the middle point of the stature of the fe- 

 male is nearer the umbihcus than in tlie male. The hips are 

 wider in proportion to the shoulders, whence the femora are 

 more oblique. The ridges and muscular processes of all the 

 bones are less marked, and the frontal contour of the skull is 

 more sharply angulated. When the peculiarities of the female 

 sex are not connected with rej)roduction, they may be said to 

 be infantile. 



The different persistent modifications or " races " of man- 

 kind present a very considerable amount of variation in their 

 anatomical characteristics. The color of the skin varies from 

 a very pale reddish brown — of the so-called " white " races — > 



