214 Journal of Comparative Neurology and Psychology. 



the curv^es for the areas of the dorsal roots (Ingbert, June, 

 1903. p. 61). 



,-. Discussion of Figs, i and 2. — The three curves in Fig. 

 I are based on the absolute areas of the cross-sections of the 

 ventral roots of the left spinal nerves, and show a general sim- 

 ilarity. Thus, they all show C. Ill smaller than C. II. A 

 marked elevation for the roots innervating the muscles of the 

 limbs and a depression for the thoracic roots is evident : Yet 

 individual roots may vary considerably in area. In Kollikek's 

 curve the largest cervical root is C. VII, a root considerably 

 diminished in the author's curve and in Stilling's. Again, C. V 

 is larsfe in Stilling's and author's curves, but not so in Koi.li- 

 ker's. In all, there seems to be a tendency to a depression at 

 C. VI. The interesting fact in connection with these points is 

 that C. V-VI correspond roughly to the roots innervating the 

 muscles of the shoulder and upper arm, and C. VII to the in- 

 trinsic muscles of the hand. In the lumbar region attention is 

 called to the position of the curve between L. Ill and S. II, 

 which exhibits two elevations bounding an intervening depres- 

 sion represented by one or two roots. In the curve from the 

 author's data the first elevation is at L. Ill, and the second at 

 L. V, with L. IV depressed. Here L. Ill represents the root 

 partly innervating the main flexors of the leg and foot. It is also 

 evident that the largest root in the cervical or lumbar regions 

 may be shifted one or more segments cephalad or caudad from 

 an intermediate position. The three curves in Fig. 2 are based 

 on the areas represented as percentages of the largest root in 

 each series. The discussion of Fig. i applies to this figure 

 also. 



IV. Deterniination of the Nuiuhcr of Nerve Fibers in the J^oi- 

 tral Roots of the Left Spinal A^erves of Ulan. 



As the study of the number of nerve fibers in the ventral 

 roots was carried on in a manner similar to that used for the 

 dorsal roots, the reader is referred to the preceding paper (Ing- 

 bert, June, 1903, pp. 62-67) ^01' "^ general statement of the 

 technique and sources of error. Certain specific statements, 



