Ingbert, Ventral Roots of Spinal Nerves. 2 1 5 



however, require to be made concerning the ventral roots, and 

 these will be given as briefly as possible. 



/. Stilling s Estimate. — Stilling (1859, P- 600) counted 

 in a series of squares 1-156 of a squre line in area, the number 

 of cross-sectioned nerve fibers seen within them, and from this 

 estimated the the number for an entire square line.^ This he 

 found to be from 120 to 156, average 138, for the ventral roots. 

 He does not state what roots he examined, nor how many 

 counts were made. If 1-156 of a square line of the section 

 contains 138 fibers, one square line will contain 156 X 138, or 

 21,528 fibers, which is equal to 4231 fibers for each square 

 millimeter. Since in his case there were 35.23 mm", in the 

 area of the ventral roots of the 31 left spinal nerves, there will be 

 35.23 X 4231, or 149,058 nerve fibers in all of them. And 

 since the right ventral roots were found to have an area of 37. 17 

 mm", they will have 37.13 X 4-231 or 157,266 nerve fibers, 

 and the ventral roots of both sides, 306,324. 



Stilling's estimate for the number of nerve fibers in the 

 ventral roots of both sides is, however, not 306,324 but 303,- 

 265. This difference is due to the fact that he based his final 

 estimate on the area of ventral roots as obtained by his method 

 of weighing, which gave 71.697 mm" for both sides, and the 

 calculations I have made are based on his areas as obtained by 

 the planimeter, which give 72.40 mm". The latter areas were 

 selected because they may be more properly compared with my 

 own, which were also obtained by planimetric measurements. 



2. AutJior s Emuneration. — By the methods and under the 

 conditions referred to in the earlier paper there were found in 

 all ventral roots of the spinal nerves of the left side 203,700 

 nerve fibers. The details of this enumeration are given in the 

 accompanying Table II. 



In Tables VIII-XXXVIII are to be found the numbers of 

 nerve fibers for each fascicle, and in Table II are found the 

 totals for each root. 



1 Stilling used the Paris line, tlie value of which is 2.255S mm. 



