( 309 ) 
If, in experimenting on a dog, two succeeding pairs of roots, 
without any more, are carefully cut through, the result is not — as 
might be expected — an uninterrupted analgetic area all round the 
trunk, similar to that found often after isolation of a dermatoma 
above and beneath the sensible area, but two analgetic triangles, 
separated by a highly sensible, usually hyperalgetic area. 
In this case too, a hyperalgetic area encompasses on both sides 
the analgetic areas. (See fig. 10). 
d 
Fig. 10. Consequences of cutting through two succeeding pairs of roots of the chest 
The insensible (dotted) area has been divided into two triangles by a hyper- 
algetic band on the lateral boundary-line. Towards the mid-ventral line the 
insensible area is much broader than towards the mid-dorsal line. 
The first fact cannot possibly be made intelligible — and this 
communication is only aiming thereat — without taking note of 
other experiments, made on carefully isolated dermatomata, whose 
central areas must be as large as possible, and without some knowledge 
at least of the ranging of the trunkdermatomata. 
In the first place the analgetic band, that has been found after 
the isolation of one trunkdermatoma above and beneath the sensible 
area, demands a closer examination. 
If the boundaries of the analgetic bands on the animal under 
experiment are designated by black or white stripes on the skin, 
and if then a photograph be taken from the animal (after measuring 
the breadth of the sensible and insensible areas on those spots that 
are judged of some importance), the thus obtained photographs will 
procure a lasting image of the changes found on the day after the 
operation. 
Reproductions of such photos may not always be of use for sub- 
sequent measurings. Therefore the simpler method may be sometimes 
21 
Proceedings Royal Acad. Amsterdam. Vol. IV. 
