(518) 
breadth in the lateral part of the dermatoma, but are also consider- 
ably broader there than at any other. place. 
This fact, considered in its connexion with our former communi- 
cations, is of the highest importance. 
Indeed, when we first found it necessary to distinguish in the 
dermatoma between a central and a marginal area, we were at the 
same time obliged to consider these two as two variable quantities, 
suffering mutual interchange of action. 
As soon as the dermatoma is damaged, the marginal area becomes 
larger according: to definite rules, whilst the central area, also 
according to definite rules, is diminished first to a triangular figure 
(fig. 2—4)') which afterwards in the lateral part is interrupted by 
an insensible band (fig. 5). 
In this place is located the relative minimum for the sensibility 
of the central area,!) but at the same time, as has been made clear 
by the foregoing, it is at this place too that the central area is 
broadest. 
Every serious operative lesion, and more especially a partly sec- 
tioning of root-bundles in the posterior root, will create the possi- 
bility of central areas being formed, not properly fulfilling their 
functions. 
By not properly fulfilled functions is meant here: the threshold- 
value for the sensibility being raised, or the marginal area being 
enlarged at the expense of the central area. 
This diminished action evidently will become most obvious at the 
place where a very broad central area possesses a relative minimum 
of sensibility. 
By this fact an apparent contradiction is solved. The obtained 
results were viz.: in the case of one or two roots being simply sec- 
tioned without any more, interrupted analgetic areas, *) and in 
the case. of one root being left intact, between two sectioned roots 
on either side of it, continuous analgetic bands. 
In the latter case the larger bone-wound, the greater hemorrhage, 
the increased cooling of the spinal medulla, furnish so many un- 
favourable conditions, by means of which, during the first days at 
least, are originated central areas of the isolated dermatoma, not 
properly fulfilling their functions. 
1) See: Proceedings of the Royal Acad. of Sciences. Meeting of Nov. 30th 1901, 
pag. 281, Fig. 8. 
2) See: Proceedings of the Royal Acad. of Sciences, Meeting of Dec. 28th 1901, 
pag. 361, Fig. 10, 
