ANATOMICAL STRUCTURE OF ANTHROPOID APES. 127 



the requirements of a given animal, that part 

 of the bone which belongs to the sections of the 

 breast and loins is more or less abundaut, and the 

 vertebrae are homologous in accordance with their 

 region, and not with their number. 



HoU has asserted that one vertebra is in close 

 connection with the ilium, joined with it through- 

 out its extent, and that this vertebra at the same 

 time always appears to support the pelvis. This 

 vertebra is, in normal cases, the first sacral vertebra, 

 and the twenty-fifth of the series. It may be termed, 

 as Welcker suggests, vertebra fulcraUs. Such a 

 main support is found, according to Holl, in every 

 vertebral column, however anomalous its other con- 

 ditions may be, and the only irregularity consists 

 in its number in the series. This bone serves as a 

 natural starting-point in our division of the vertebral 

 column. The vertebra fulcraUs must always be 

 regarded as the first sacral vertebra. It begins the 

 series of sacral vertebra, and, on account of its sub- 

 sequently important position, it must be regarded as 

 primary. Holl finds that it is followed by four lower 

 vertebra?, which are afterwards included with it in 

 the sacrum. When in its primary condition the ver- 

 tebra fulcraUs is tw. nty-filth in the series, the twenty- 

 fifth to the twenty-ninth vertebras are included in 

 the sacrum. When the fulcraUs is the twenty-sixth 

 vertebra, the sacrum includes the thirtieth. Hence 

 it follows that the sacrum is, from the first stages of 

 its development, a formation which begins with the 

 twenty-fifth or twenty-sixth vertebra, and includes 

 four other vertebrae. Holl considers that the lumbo- 



