Ingbert, Ventral Roots of Spinal Nerves. 217 



4. The uniformity of the number of fibers in the thoracic 



roots. 



5. The number of fibers in the largest cervical root, which 



is twice the average number in the thoracic roots. 



6. The large roots in the lumbo-sacral region — L. Ill — 



innervating in part the adductors and flexors of the 

 thigh ; and L. V — innervating in part the flexors of leg 

 and foot. 



7. The depression at L. IV — corresponding to the demar- 



cation between the lumbar and the sacral plexuses. 



8. In this case — a male — the four largest cervical roots 



(C.V, VI, VII, VIII) contain more fibers than the 

 four largest successive lumbo-sacral roots (L. Ill, IV, 

 V andS. I.) 



9. That the number of nerve-fibers per sq. mm. of the 



cross-section of the ventral roots shows that the fibers 

 in the roots passing to the brachial and the lumbo- 

 sacral plexuses have an average diameter which is 

 large, and that the fibers in the thoracic roots have an 

 average diameter which is small. 

 J. Comparison of Stilling s Estimate ivitli the AutJior s Enu- 

 meration. — The determinations of the number of meduUated 

 nerve fibers in the ventral roots of the left spinal nerves of man 

 in the case which we have just discussed, give the following 

 result : 



Author's Enumeration 203,700 nerve fibers. 

 This result shows that Stilling's estimate, 149,057, is 

 73.17^ of the author's enumeration, or, in other words, the 

 author's result is 26.83% greater than Stilling's. On search- 

 ing for the cause of this difference, we find two significant state- 

 ments made by Stilling. First, he says that he did not ob- 

 serve in either the ventral or the dorsal spinal roots (at least 

 not in the material fixed in chromic acid), nerve fibers of such 

 diameters as Kolliker reports (2.7 to 4. 5 /i); and secondly, that 

 the diameters of the meduUated nerve fibers in the ventral roots 

 range from 7.5 to 22.5 // (Stilling, 1859, P- ^Z^)- It is thus 

 evident that one source of difference between Stilling's esti- 



