(524) 
marginal areas in the structure of the dermatomata, for under normal 
conditions the ventral part is sensible over its whole extension. But 
the smaller dorsal analgetie triangle, which should be formed at the 
mid-dorsal line is never observed. This again argues the existence of 
marginal areas — or, if one prefers, parts of the dermatoma, whose 
sensibility remains below the threshold-value — of the neighbouring 
dermatomata, being able of providing together in the sensibility of 
this band, as soon as one dermatoma has been taken away, though 
unable of doing so alone. 
As soon however as two dermatomata (4 and 5) are taken away, 
there is formed a double triangle; marked with +-+. In the lateral 
part an interruption will necessarily occur, because in that part the 
overlapping of the central areas is so great, that the 3 and 
6th dermatoma are situated in very close proximity, even touching 
one another. 
The relative minimum of the central area, here drawn out to its 
largest breadth, is cause of different facts: the contrast between 
central and marginal area being at one time very slight, and then 
again very striking. If the central area has been isolated under very 
favourable circumstances, performing its functions in the best possible 
way, there will be hardly any question here about a marginal area. If 
on the contrary it has been isolated, not fulfilling its functions so 
well, then this part of the central area falls wholly or almost wholly 
below the threshold-value. It then becomes totally or nearly totally 
marginal area, and the lateral insensible interruption of the central area 
is brought about. 
We conclude from the foregoing that the improvement of sensi- 
bility in the first 4 or 5 days after the operation, is achieved solely 
by parts of marginal areas being joined to the central area. Accor- 
ding to our belief, in no other manner any improvement of sensibility 
may be achieved, at least during some months. The results, observed 
consequently to similar operations after the first fortnight, are found 
unaltered after six weeks or three months. 
