34 



there is a tendency for the spine to assume as nearly as possible its 

 normal disposition and proportions. This, as do also concomitant 

 variations and indeed all development, implies a vital principle." 



Several important papers have since appeared containing valuable 

 additions to our knowledge. It is proposed to consider particularly 

 the work of Bardeen^), that of Adolphi 2), and that of Ancel and 

 Sencert 3). 



Bardeen's investigations are in one respect of paramount im- 

 portance in as much as they controvert Rosenberg's observations and 

 destroy his hypothesis, which while denied by some has been raised 

 by others to the dignity of a law, so that systems have been accepted 

 or rejected according as they conformed to or differed from it, 



Bardeen shows that the original position of the ilium is opposite 

 the anterior part of the lumbar region and that in development it 

 travels backwards instead of forwards. Moreover when it has once 

 joined a vertebra it never leaves it. All of which is in direct contra- 

 diction to Rosenberg's system. The junction of the spine and the 

 ilium occurs at about the end of the fifth week. No chondrofication 

 has yet occurred, but there is no subsequent change in segmentation. 

 "The thoracic vertebrae are differentiated from the others even at this 

 early period." 



Bardeen goes on to say "regional variation in the vertebral column 

 is an inherited condition which makes itself manifest early in embryonic 

 development. A sufficient number of individuals of a given race would 

 probably show the same frequency of regional vertebral variation 

 throughout the course of development from the sixth week to the 

 adult condition." Precisely what it meant by calling regional variation 

 an inherited condition is not clear. If it means that the tendency to 

 variation is inherited, there can be no question of the correctness of 

 the statement. But if it means that particular variations are inherited, 

 it cannot be accepted, for a spine with twenty-five praesacral vertebrae 

 and one with twenty- three cannot both be explained by inheritance. 

 An essential point, however, is that variation occurs before the sixth 

 week, be its cause what it may. Passing over Bardeen's conclusions 

 on difference of variation . in race and in sex, we come to his last and 



1) Numerical Variation in the Human Adult and Embryo. Anat. 

 Anz., Bd. 25, 1904. — The Development of the Thoracic vertebrae in 

 Man. The American Journ. of Anat., Vol. 4, No. 2, 1905. — Studies 

 of the development of the Human Skeleton. Ibid., 1905, No. 3. 



2) Morphol. Jahrb., Bd. 33, 1905. 



3) Journ. de I'Anat., T. 38, 1902; Bibliogr. anat., T. 10, 1902. 



