40 



THE STRUCTURE OF MAN 



the lumbar vertebrae (Fig. 24, rl), and in the sacral region also 

 (Fig. 25, B r.s.). 1 From this it is clear that the pelvis in Man, 



r.th. I 



FIG. 24. PART OF THE THORACIC, AND THE WHOLE LUMBAR, SACRAL, AND 

 COCCYGEAL SECTIONS OF A YOUNG HUMAN VERTEBRAL COLUMN. (Dorsal aspect.) 

 The lateral processes of the first to the fifth lumbar vertebra are on one side prolonged 

 (by dotted lines) for diagrammatic delineation of the formerly existing lumbar ribs 

 (r.l.), which are present in the embryo. The sacrum is still subdivided into its five 

 component parts, i.e. consists of five distinct vertebrae (v.s.). v.c., caudal (coccygeal) 

 vertebrae ; r.th., the three lower thoracic ribs. 



like that of all terrestrial Vertebrates, is carried by ribs, which, 

 however, become early united with the sacral transverse processes. 



1 In the twenty-first and twenty-second pre-sacral vertebras of the embryo, the 

 ribs are still separated from the vertebral arches by membranous tissue, but in 

 the succeeding vertebrae they are more and more completely united with them. It 

 would thus appear that the reduced ribs are early incorporated in the so-called trans- 

 verse processes of the lumbar vertebrae. 



