OF THE SKELETON. 407 



portions of the skeleton, and not merely its dimensions under- 

 go great changes through age.* 



The proportion of the head to the rest of the trunk and to 

 the limbs is so much the greater, the younger the subject is, 

 only within the twentieth year. At the second month after 

 conception, it forms half the height of the body, nearly the 

 fourth at birth, the fifth when three years old, and the eighth 

 only when the growth is complete. The face in like manner 

 is so much the smaller, compared with the skull; the pelvis, 

 compared with the thorax, the limbs compared with the 

 trunk, &c. the younger the subject is. Many other differences 

 of the same kind will be pointed out in the particular anatomy 

 of the bones. 



645. The skeleton presents pretty distinct differences in 

 the two sexes, t In general the skeleton of the female is smaller 

 and more delicate than that of the male; the thorax is shorter, 

 and altogether smaller; it is also more mobile; the pelvis 

 broader; the lumbar region more elongated, &c. The diar- 

 throdial articulations are more mobile, the amphiarthrosis more 

 flexible, &c. All the regions of the body, and almost all the 

 bones, present some particular differences. 



646. The human races also present differences in their 

 skeleton, the principal of which have reference to the dimen- 

 sions and form of the skull, and its proportion to the face.J 

 There are also some differences in the proportions of the limbs. 

 In the negro race, the upper limbs are longer in proportion to 

 the trunk; the fore-arm and leg are longer proportionally to 

 the arm and thigh. 



647. Lastly, individual varieties are observed in the 



* Boehmer. op. cit. Cheselden, op. cit. Eyson, op. cit. Sue, Sur les 

 Proportions du squektte de rhomrtle, examint depuis Page k plus tendre, 

 jusqu'd celui de vingt-cinq, Soixante arts et au-dela,- in Mem. Pres. vol. ii. 

 F. G. Danz, Grundriss der Zergleiderangskunde des ungebornen kindes, 

 Francoff, 1792. Senff, op. cit. 



f See J. F. Ackermann, De Discrimine Sexus prefer genitalla. Mogunt, 

 1788. Compare also Albinus, Tabula sceleti hominis, and Soemmering-, 

 Tabula scekti foeminei, Francof. ad Moenum, 1796. 



$ Blumenbach, Decades Craniorum, i.-vi. Soemmering, De Ossilus. 

 53 



