232 Jounial of Coviparative Neurology and Psychology. 



VII. On the Relative Areas of the Cross-seetions of the Roots 

 Forniing the Brachial and the Lumbosacral Plexuses in 

 the Male and the Female. 



To determine whether or not the roots of the brachial 

 and the lumbo-sacral plexuses show any difference in size in the 

 two males, (Kolliker and the author) and the two females 

 (KoLLiKER and Stilling) the spinal roots of which have been 

 measured, I have added the areas of the cross-sections of the 

 four largest ventral and dorsal roots in the cervical and the lum- 

 bar regions respectively, as given by the several authors. These 

 results may be arranged as follows : 



(a) Relation of the Area of the Cross-sections of Four Roots 

 of the Brachial Plexuses. 



2 males 2 females 



Ventral (C. V — VIII) 16. 3S mm.'-^ 16.02 mm.^ 



Dorsal (C. V — VIII) 40.04 mm.^ 21.30 mm.- 



56.42 mm." 47-3- mm.^ 



From this it is evident that the roots here compared are 

 better developed in the male, and would indicate that the males 

 have a little better motor and much better sensory inner- 

 vation for the arm. 



(b) Relation of the Area ot the Cross-sectious of Four Roots of 

 the Lumbo-sacral Plexus. 



2 males 2 females 



Ventral (L. IV, V and S. I, II) 14-36 mm.- 17-46 mm.' 



Dorsal ( " " " ") 31-04 mm.- 33--4 nim.- 



45.40 mm.- 50.70 mm.^ 



From these results it is evident that the roots here com- 

 pared are better developed in the female, and would indicate 

 that the feniales have a better motor and sensory innervation 

 of the hips and legs. 



These results may also be arranged so as to bring out the 

 relative development of these roots in the brachial as against 

 the lumbo-sacral roots in males and females. 



