507 



1) Embryos with 24 presacral vertebrae . . . .49, 89.0 °/o 



a) Normal arrangement 42, 16A% 



b) Variations at the thoracico-lumbar margin . 4, 7.3 °/o 



7 c, 11 t, 6 1, 5 s, 5 Co 



7 „ 11/12 „ 6/5 „ 5 „ 4 „ 



7 „ 11/12 „ 6/5 „ 5 „ 3 „ 



7 „ 11 „ 6 „ 5 „ 3 „ 



c) Variation in the number of sacral vertebrae . 3, 5.5 *^/o 



7 c, 12 t, 5 1, 6/5 s, 4/3 Co 

 7 „ 12 „ 5 „ 6/5 „ 5/4 „ 

 7 „ 12 „ 5 „ 6 „4 „ 



2) Embryo with 23 presacral vertebrae .... 1, 1.8 % 



7 c, 12 t, 4 1, 6 s, 4 Co 



3) Embryos with 25 presacral vertebrae .... 5, 9.0 7o 



7 c, 12 t, 6 1, 5 s 



7 „ 12 „6 „5 „4 Co 



7 „ 12 „ 5/5 „ 6/6 „ 4 „ 

 ' 77 l2 „6 „5 „3 „ 



' V 1-^ 77 " 77 5 ,5 5 „ 



Numerical variation in the vertebral column during 

 early childhood. Steinbach studied the vertebral column in the 

 bodies of 50 children (29 M., 21 F.) one year old or less. He found 

 the following variations in the precaudal region: 



{male '^81 

 „ ^ lA 49, 98.0% 



a) Normal conditions! - , ^. , 



b) Increase in number of sacral vertebrae . . . 



7 c, 12 t, 5 1, 5 s, 1 sCo, 3 Co (2) 

 2) Vertebral column with 25 presacral vertebrae . . 

 7 c, 12 t, 5 1, 1 Is, 5 s, 4 Co 

 In this lot of bodies, therefore, numerical variation occurred in but 

 6.0 "/o of instances outside of the caudal region. Since, however, the 

 attention of Steinbach was directed mainly to a study of the caudal 

 vertebrae it is possible that some variations in the regions more 

 anterior were overlooked. 



4. Adult Period. 



Many contributions have been made to the subject of variation 



in the adult vertebral column. Among the more valuable of the recent 



articles may be mentioned those of Ancel and Sencert 1901, Bolk 1901, 



Cunningham 1889, Dwight 1901, Gruber 1869, Leboucq 1898, Pa- 



