506 



fetal vertebral columns. He found a great variety of variations, as 

 may be seen in the following table, based on that in his valuable 

 monograph : 



1) Embryos with 24 presacral vertebrae .... 25, 83.3 7o 



a) Normal arrangement 18, 60.0 7o 



b) Variations marked at the thoracico-lumbar margin 4, 13.3 7o 



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 V " :? 5 „ 3 „ 



c) Variations in the number of sacral vertebrae 3, 10.0 Vo 



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

 7 „ 12 „ 5 „ 5/6 „ 5/4 „ 

 7 „ 12 „ 5 „ 6 „ 4 „ 



2) Embryos with 23 presacral vertebrae .... 1, 3.3 7o 



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



3) Embryos with 25 presacral vertebrae .... 4, 13.3 7o 



7 c, 12 t, 6 1, 5 s, 



7 „ 12 „6 „5 „4 Co 



7 „ 12 „ 5/6 „ 6/5 „ 4 „ 



♦ 5? 12 77 6 „5 „3 „ 

 In marked contrast to this great frequency of variation found by 

 Paterson in fetal columns stand the results obtained by Steinbach 

 (1889), who studied twenty-five embryos belonging to the 4th of 5th 

 and 6th months of development. 



Thus, in these 25 specimens there was found in the thoracico- 

 lumbo-sacral region variation in but one instance, 4 per cent of the 

 total number. In this instance there was an extra lumbar vertebra. 



Bade (1900) pictures 10 embryos of the stage under consideration. 

 In none of these embryos is variation in the vertebrae apparent, but 

 it is perhaps best not to include them in making up a table of ver- 

 tebral variations because the X-ray photographs admit of some un- 

 certainty of interpretation. 



Tabulating the thirty embryonic columns studied by Paterson 

 with the twenty-five studied by Steinbach, we get the following result : 



