372 THE CORRESPONDENCE BETWEEN THE [CHAI-. 



is rotated forwards, so that the pre-axial side of the first 

 becomes external, and the really corresponding side of the 

 other becomes internal, so it is with the scapula and ilium. 

 Each has undergone a rotation on its own axis, through 

 nearly a quarter of a circle, and in the opposite direction 

 (see Fig. 134, E. and F), so that the inner surface of the one 

 comes to correspond with the outer surface of the other, 

 the anterior border of the one with the posterior border of 

 the other. The long axis of each is also differently inclined, 

 the upper end of the scapula leaning backwards, while that 

 of the ilium is inclined forwards, which makes the resem- 

 blance between them seem still more obscure. 



These views are considerably strengthened by a considera- 

 tion of the disposition of the muscles connected with the 

 various bones in question. 1 



The principal differences between the shoulder and pelvic- 

 girdles of the Mammalia are two: (i) The rudimentary 

 condition of the inferior or ventral section of the girdle (the 

 coracoid) in the former, as compared with the vast deve- 

 lopment of the corresponding part of the lower extremity : 

 (2) the free condition of the anterior as compared with the 

 posterior girdle. It is neither attached to the vertebral 

 column above, nor does it (except in the Monotremata) join 

 the opposite part in the middle line below. To compensate 

 for this, a clavicle is superadded to the anterior girdle in 

 many Mammals, for which there is no exact homologue in 

 the lower extremity. 



It has been shown in Chapters XVI. and XIX. that 

 the terminal segments of each limb present a remarkable 

 general correspondence with certain constant differences. 



1 See Flower, "On the Correspondence between the Parts composing 

 the Shoulder and the Pelvic Girdles of the Mammalia." Journal of 

 Anatomy and Physiology, vol. iv. p. 239, 1870.) 



