27S Studies of the Development of tlic Human Skeleton 



A comparison of the spinal columns of embryos of the second and third 

 months with those of older embryos and of children shows that it is dur- 

 ing the latter half of foetal life and early childhood that the chief relative 

 lengthening of the lumbar region takes place. 



i\.ccording to Aeby the average length of the cervical, thoracic and 

 lumbar regions in the new-born is respectively 45.1, 83.9 and 47.5 mm. 

 This makes the length of the cervical region 53.5% and that of the 

 lumbar region 5G% of that of the thoracic. Corresponding figures from 

 Ballantyne, 92, for full-term foetuses are: cervical, 33.6 mm. (42.8%) ; 

 thoracic, 78.4 mm. (100%); lumbar, 42.8 mm. (54.3%); and sacro- 

 coccygeal, 39.8 mm. (50.8%). Thus Ballantyne finds a greater propor- 

 tional reduction of the cervical region. 



The conditions in the adult, as given by various investigators, are as 

 follows : 



TABLE B. 



The chief point of interest in this table is the difference between the 

 results found by the German and American investigators and those of the 

 Italian. Apparently the Italians have proportionately shorter cervical 

 and lumbar regions than the Americans and Germans, but it is possible 

 that different ways of measuring were used. It is a subject worthy of 

 further investigation. 



Both Tenchini and Ancel and Sencert, 02, have treated of variations 

 in measured length of individual vertebrae associated with numerical 

 vertebral variation. 



