234 fournal of Comparative Neurology and Psyeliology. 



largest dorsal and ventral cervical roots (C. V-VIII) is 

 greater than that of the corresponding roots of two 

 females, and also greater than that of the four largest 

 lumbo-sacral roots (L. IV-V and S. I-II) of the same 

 males (pp. 232-233). 



7. In two female cords the sum of the areas of the four 

 largest ventral and dorsal cervical roots (C. V-VIII) is 

 less than that of the corresponding roots of the two 

 male spinal cords, and also less than that of the four 

 largest lumbo-sacral roots (L. IV-V^ and S. I-II) of the 

 same females. This shows that in the male, the roots 

 contributing to the cervical plexuses, and in the female, 

 the roots contributing to the lumbo-sacral plexuses, are 

 the better developed (pp. 232-233). 



(B) Nl'MllER (IF FIKERS. 



8. The total number of medullated nerve fibers in the ven- 

 tral roots of the left spinal nerves of the same man is 

 203,700; and the total number on both sides would 

 therefore be about 407,400 (Table II). 



9. Since, according to the author's enumeration, there are 

 203,700 medullated nerve fibers in the ventral roots of 

 the left spinal nerves, and 653,627 in the dorsal, the 

 ratio of the number of fibers is 1:3.2 (Table VI). 



10. In the increase of the nerve supply to the limbs, the 

 gain has been far more in the sensory than in the motor 

 fibers (page 230). 



11. The ratio between the number of fibers in the ventral 

 and dorsal roots of man is 1:3.2 (Ingbekt), of the white 

 rat 1:2.3 (Hat.ai); and the frog 1:1.2 (Birge). From 

 this we may conclude that probably the relative sensory 

 supply increases as we ascend in the zoological series. 



(C) SIZE OK FUiERS. 



12. According to the author's estimates, there are about 

 80,747 (39. I ^r) fine fibers (less than 7.5 ji.) in the ven- 

 tral roots, and 381,176 (60%) fine fibers (less than 

 7. I j).) in the dorsal roots — in other words, the ratio of 



