C^H7 



not coincide exactly with (he (hn-sal l)onn(hii'y of the ventral area, 

 but that a reeiprccal overlapping occurs, although it be only a 

 slight one. It is shown thereby that the lient, found in the demar- 

 cationline of the root-area, is situated exactly at the point where the 

 dorsal and latero-ventral portions of the dermatoma meet. The cranial 

 direction of this bent indicates that the latero-ventral portion must 

 be lying somewhat more cranialward than the dorsal one. This fact 

 has been stated previously by Bolk ^), when he found in 1897 a 

 "discrepancy" of the dorsal and ventral dermatoma-areas on the 

 human trunk. In the experimentally defined dermatoma this discre- 

 pancy finds its expression in the alleged "bent". Similar conditions 

 have been observed clinically by Eichhorst '"), after transversal lesions 

 of the spinal cord in the trunk-area. 



c. Interruption of the conduction in separate minor branches of the 

 dorsal and latero-ventral nerves. 



The conduction may be interrupted in the separate minor branches 

 of the perforating nerves as well in the dorsal as in the latero-ventral 

 portion of the root-area. When this operation has been performed it 

 becomes evident, as long as only the larger branches were sulijected 

 to it, that each of these supplies the innervation of a small zone, 

 extending equally into the cranial and into the caudal boundaiy of 

 the root-area, and for the rest demarcated by lines going in a 

 cranio-caudal direction. The whole root-area therefore is divided 

 into a series of small areas, lying alongside of one another in 

 dorso-ventral direction. The skin-area of the medio-dorsal branch 

 adjoins the mid-dorsal line, the dorso-lateral branch on the other 

 hand extends over an area, adjacent to the lateral portion of the 

 dermatoma, more ventralward than that of the medio-dorsal branch. 

 A similar ordination is found likewise to exist for all skin-areas 

 corresponding to the various latero-ventral branches. 



Whenever very thin branches are cut through, either no insensi- 

 bility ensues, or else an irregularly insensible spot is found some- 

 where within the root-area. From the fact that in many cases, after 

 the sectioning of such small branches, no insensibility is found, we 

 may conclude that the areas of extension of the separate branches 

 of the cutaneous nerves must overlap one another to a certain degree. 

 I have not been able however to determine the extension of these 

 overlappings. 



1) L. BoLK, A. few data fiotn the segmental anatomy of the human body. 

 Ned. Tijdschrift v. Geneeskunde. 1897. I p. 98-2—995, and 1897. 11. p. 865-379. 

 (Compare especially p. 366 et seq.). 



2) H. Eichhorst, Verbieilungsweise der Haulnerven beim Menschen. Zeilsclir. 

 f. Klin. Medicin. Bd. XIV. S. 519. Berlin 1888. 



