114 Miss M. P. FitzGerald. The Lumbosacral-coccygeal [June 17, 



m, ,. white substance , . , , , . „ ,, 



Ihe ratio having been determined for the upper, middle, 



grey substance 



and lower portions of the region of each spinal nerve, a mean of the three 

 ratios has been employed in the curve to represent the ratio of the region.* 



E w w v "VT vir 



n m tv 



ir nr. 































































.1 



\ 



\ 

































a 



N. 



\ 



















G 











4 



s 



J> 























I it m tv v vr. ve i n' m w > i nm 

 Lupvbcur Sacral CoccyqeaZ 



Chart IX. — Curves showing the Ratio of the total "White Substance (W, continuous line), 

 of the Dorsal White Columns (P, broken line), and of the Ventrolateral White Columns 

 (A, line and dot) to the Grey Substance (G). 

 The grey substance is taken as unity in each cross-section of the cord. Mean results 

 are plotted (Table VIII). The abscissa? denote the spinal nerve regions, the ordinates the 

 ratio at the corresponding regions. 



Eati0 white substance (W) ^ JX ^ ym 

 grey substance (Gr) 



m, total white substance (W) j , • 1 » t 



The ratio ; ^-^decreases continuously from the first 



grey substance (Gr) 



lumbar to the first coccygeal region. From the first to the third coccygeal 



region a very slight increase occurs. 



The decrease in the ratio is very rapid from the first to the seventh lumbar 



region, and is most conspicuous in the first three lumbar regions. In the 



seventh lumbar and through the first three sacral regions the decrease in the 



ratio is scarcely perceptible. In the fourth sacral region the ratio is as 1 : 1, 



and while in the first and second coccygeal regions it is slightly less, equality 



is again reached in the third coccygeal region. 



* The same remark applies to all subsequent curves illustrating ratio. 



