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24th, the 25th, or even the 26th? According to Rosenberg, and 

 probably most biologists, the former view is to be adopted. On the 

 other hand, in my opinion, if it can be shown that a certain vertebra 

 has a distinct teleological significance, it is an excellent starting point. 

 Welcker's idea of a vertebra fulcralis is a very valuable one. It 

 is the vertebra, normally the 25th, which has the most to do in sup- 

 porting the ilium, as is shown by its forming a larger part of the 

 auricular surface than any other. According to Welcker this vertebra 

 is always to be compared to the one having a similar function, be 

 the number what it may. He goes even further and would have 

 not only the whole praesacral region of one spine correspond with 

 that of another, but he would have its component regions correspond 

 respectively with those of other spines. While I fully adopt the former 

 view, I am not sure that it is wise to attempt to carry it into such 

 details. There is, however, one serious difficulty. The fact that a 

 vertebra is the fulcralis is established by its being the one that 

 forms the largest part of the auricular surface, thus bearing more of 

 the ilium than any other, not by its general shape. This is particularly 

 insisted upon by Holl, who adopts the idea. It is common enough 

 for it to be the 26th instead of the 25th, in which case there is rarely 

 any difficulty in deciding which vertebra is the fulcralis. Holl 

 declares he never has known the 24th to be the fulcralis, though 

 he has seen it so sacralized that at first he was inclined to think so. 

 In the present series there are several in which it is certain that the 

 24th is the fulcralis, but there are also some in which it is very 

 difficult or, rather, nearly impossible to decide whether the 24th or 

 the 25th be the fulcralis. Does this difficulty do away with the 

 conception of a vertebra fulcralis altogether? I think not. There 

 is nothing in the human body that is not variable, and why should 

 we exact absolute stability from the vertebra fulcralis? 



The vital principle. My reasons for accepting the idea of 

 the vertebra fulcralis are the following: Every living organism 

 has the tendency to develop in a certain way to adapt itself to certain 

 purposes. The fact that under changed circumstances there may be 

 a change in development, distinctly strengthens the theory. This ten- 

 dency makes for the good of the organism as a whole, which is some- 

 thing more than an agglomeration of fortuitous parts. Whithout this 

 unifying principle the harmonious development of the various parts 

 is incomprehensible. An essential part of the office of the spine is to 

 form the median support of the trunk. The part above the pelvis 

 niay be considered as an apparatus with several functions. It is there- 



