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



throughout the regions of the sacral nerves. A slight decrease in the first 

 coccygeal is followed by an increase in the second and third coccygeal 

 regions, the increase being marked in the third. 



B7. Relative Increase and Decrease in the Section Area of the Cord and of 



each of its Component Parts. 



A general idea of the relative increase and decrease in the section area of 

 the cord and of its component parts is to be obtained from the following 

 table (XX) and Chart XIX. 



The section area of each constituent of the cord at the particular region in 

 which it reaches a maximum value is taken as 100. For the cord as a whole, 

 and for the white substance and its component parts — the dorsal and the 

 ventro-lateral columns — this region is the fourth lumbar; for the grey 

 substance and its component parts — the dorsal and the ventral horns — the 

 fifth lumbar. 



The mean figures obtained from the three sections taken in each region 

 were employed (Table XX) in drawing the chart : — 



Table XX. — The Section Area of the Cord and of each of its Component 

 Parts at its Maximum Value is taken as 100. The Table gives the 

 mean percentage values of the cross-section of the cord and of each 

 of its component parts in the region of each spinal nerve (Chart 

 XIX). 



Region of 

 cord. 



Cross- 

 section 

 of cord. 



Grey 

 substance. 



Dorsal 

 horns. 



Ventral 

 liorns. 



White 

 substance. 



Dorsal 

 columns. 



Ventro- 

 lateral 

 columns. 



Lumbar — 

















I 



64 



34 



56 



26 



80 



80 



78 



II 



71 



46 



73 



37 



83 



87 



80 



III 



76 



55 



69 



51 



85 



88 



82 



IV 



100 



87 



84 



88 



100 



100 



100 



T , , 



94 



100 



100 



100 



89 



82 



90 



VI 



73 



82 



92 



78 



64 



54 



67 



VII 



53 



63 



90 



53 



45 



38 



46 



Sacral — 

















I 



39 



47 



76 



37 



32 



25 



35 



II 



29 



35 



58 



27 



24 



19 



26 



III 



22 



27 



45 



20 



18 



14 



19 



IV 



17 



21 



39 



15 



13 



11 



14 



Coccygeal — 

















I 



12 



17 



31 



11 



9 



7 



10 



II 



7 



9 



18 



6 



5 



4 



5 



III 



3 



4 



10 



2 



3 



1 



3 



