16 Proceedings of the Royal Physical Society. 



the vertebral column and the attached sacrum are swung 

 between the two iliac bones. Of course these ligaments 

 possess an importance and a strength not found among 

 animals whose gait is horizontal. By far the most interest- 

 ing of the sacral ligaments, however, are those which connect 

 the hinder end of the sacrum and the coccyx with the 

 ischium — the great and small sacro-sciatic ligaments. Their 

 function is to act as " stays," preventing the front end of the 

 sacrum from being borne downwards by the weight which it 

 carries. Accordingly they are highly developed in man, 

 since the entire weight of his trunk and upper limbs is 

 placed upon the front end of his sacrum. Not only are they 

 of great strength in man, but their attachments have ex- 

 tended backwards, until the coccyx has become included 

 between them, with the result that the agitator caudce 

 muscle is no longer able to effect the purpose expressed in 

 its name, and accordingly it has fused with the gluteus 

 maximus. Further, it is to the smaller of the two sacro- 

 sciatic ligaments that the spine of the ischium is mainly 

 due. Although it is very difficult, if not practically impos- 

 sible, to record the exact length of the ischial spine, yet it is 

 a most characteristic human feature. 



Again, if the necessary data were available, it would be 

 found that the length of these ligaments — in other words, 

 the distance between the sacrum and ischium — steadily 

 diminished in passiug from the horizontal to the erect 

 attitude. The record of the shortest distance between the 

 tuberosity of the ischium and the lower end of the sacrum 

 would afford a valuable addition to pelvic measurements 

 in relation to the question of race. In proportion as this 

 distance diminishes, so the outlet of the pelvis is reduced, 

 and the difficulty of Labour therefore increases, solely on 

 account of the assumption of the erect attitude. 



The bones of the extremities present numerous evidences 

 of their evolution from forms characteristic of lower animals. 

 In the case of each bone, its racial character correlates the 

 higher and more civilised races with the lower and more 

 primitive, while the latter, in their turn, are correlated to 

 the anthropoid apes, and, through them, with still lower 



