Vice- President's Address. 15 



erect attitude. These muscles are situated within the pelvis, 

 and in mammals generally, they play the part of retractors 

 of the lower end of the bowel. In man, on the other hand, 

 they serve chiefly to form a muscular floor for the pelvis in 

 association with the erect attitude; and, as a result, some 

 part, at least, in the production of his prominent ischial 

 spine may be credited to the levator ani muscle. 



III. The Osseous and Articulatory Systems. 



In the vertebral column, variations affecting the number 

 of vertebrae are not frequent, nor are structural deviations 

 common. Such as do occur mostly pertain to imperfections 

 in the process of ossification. These are of more frequent 

 appearance among lower than among higher races, and, again, 

 more frequent among lower animals than among men. It is 

 quite evident that the erect attitude depends upon the 

 stability of the vertebral column. 



The production of a sacrum through the fusion of a certain 

 number of vertebrae is of immense interest. At first sight it 

 does not appear clear why the hind limbs of a horizontal 

 animal should require this kind of attachment, and not the 

 fore limbs, although in all probability the mechanism of 

 respiration acts more freely in association with articulated, 

 rather than with fused vertebrae. At any rate, the position 

 of the sacrum, the number of bones which enter into its 

 formation, and its ligamentous connections with the inno- 

 minate bones, are all characteristic, and indicative of evolu- 

 tion in the human subject. 



The variations in its dimensions are sufficiently marked to 

 establish not only a race-character for this bone, but to cor- 

 relate the sacrum of lower races with that of lower animals. 



As regards man, the assumption of the erect attitude has 

 led to important evolutions of its ligamentous connections. 

 Thus, at the upper end of the sacrum the ligaments of the 

 vertebral column are prolonged, so as to enable the super- 

 incumbent weight to be carried by the sacrum without fear 

 of slipping off. On the posterior aspect of the sacrum, very 

 powerful ligaments attach it to the ilium, so that in reality 



