322 



cal School, which, with one exception, were obtained by me in the 

 dissecting room. It represents many years' work. There are not only 

 series representing many grades of certain peculiarities, but some 

 specimens which I believe are unique, and others which are extremely 

 rare. These spines are all ligamentous preparations. I have carried 

 the principle of ligamentous preparation to such an extent as to throw 

 aside some good specimens in which the preliminary maceration had 

 unfortunately been excessive. In two or three cases the atlas is lost, 

 and in several the coccyx is more or less incomplete. At least once 

 the sacrum is imperfect. Besides these spines there are several parts 

 of the column, mostly of my collecting, which are described later. 

 Some of the latter are mentioned by way of showing all that is in 

 the collection; but some of them are intrinsically valuable. 



The purpose of this paper is both to discuss what these, spines 

 teach concerning the significance of numerical variation of the vertebrae, 

 which opens many important scientific questions, and to make the 

 collection available to others. 



Rosenberg's system. The paper which, beyond all doubt, has- 

 had the most important iüflueuce on this question is that of Rosen-. 

 BERG which he has lately supplemented by another containing a de- 

 scription of a spine with two additional praesacral vertebrae and 

 15 ribs, of which one pair is cervical ^). It is needless to repeat 

 Rosenberg's well known theory, especially as in his last paper he 

 states the deductions to be made from it very comprehensively. He 

 considers (as he did before) the middle part of the thoracic region 

 of the spine as the most primitive, and holds that the division of the 

 column into regions (not only in man, but also in other mammals, 

 and indeed in other vertebrates) is the work of two chief factors 

 which simultaneously, and to a certain extent in the same manner, 

 exert an influence on the column in opposite directions. "These factor* |' 

 are both processes of transformation, of which the one, acting on the 

 smaller proximal (i. e. cervical) division of the column, works distally ; 

 while the other, affecting the greater distal (i. e. lumbar, sacral and 

 caudad divisions) works proxiraally." In other words the cervical 

 region on the one side and the lumbar on the other tend to absorb 

 into themselves the thoracic vertebrae nearest to them. Such a change 



Natural History, "Vol. 5. It is published in order to call the atteu.tion 

 of my colleagues to the original, which many of them might not see 

 otherwise. 



1) Morphol. Jahrb., Bd. 17, 1899. 



