2 1 o Journal of Comparative Neurology and Psychology. 

 I. Introduction. 



Having completed "The Enumeration of the MeduUated 

 Nerve Fibers in Dorsal Roots of the Spinal Nerves of Man" 

 (June, 1903), the author attempted to determine how many of 

 these dorsal root fibers innervated the muscles and other deep 

 tissues, and how many, the skin. For this purpose it was nec- 

 essary first to determine the number of nerve fibers in the ven- 

 tral roots. This was done. Using the number obtained in 

 this enumeration, an estimate was made "On the Density of the 

 Cutaneous Innervation in Man" (October, 1903). 



The purpose of this present paper is to give in detail the 

 results obtained from the study of the number of fibers in the 

 ventral roots. 



//. Historical Statement. 



Although estimations of the number of meduUated nerve 

 fibers in different spinal and cerebral nerves of man and de- 

 terminations of the areas of their cross-sections have been made 

 by D. Rosenthal (1845), Stilling (1859), Tergast (1872), 

 KuHNT (1879), W. Krause (1876 and 1880), Salzer (1880), 

 and VoiscHViLLO (1883), no complete count of the spinal nerves 

 had been made prior to the author's observations cited above 

 (June, 1903). We are now able to add a similar enumeration 

 of the meduUated nerve fibers in the ventral roots of the spinal 

 nerves of the same man. For a description of the material, the 

 reader is referred to the paper first mentioned above. 



///. Determinatio'd of the Areas of the Cross-Sections of the 

 Ventral Roots of the Spinal Nerves of Man. 



I. Kolliker s Determination. — Under conditions which 

 have been described elsewhere in detail (Ingbert, June, 1903, 

 p. 55), Kolliker (1850, p. 434) determined the area of all the 

 cross-sections of all ^ the ventral roots of the left spinal nerves 



* Kolliker does not give the areas of the ventral roots of the sacral nerve 

 IV and V. We estimate their combined area as about 0.2 mm'^ and have cor- 

 rected his results by adding this amount. 



