152 
zone here deseribed, as 2:3. (In reality the proportions were 35 : 55). 
It is certainly peculiar, that this proportion 2:3 expresses exactly 
the “stretching” of the ventral skin (from manubrinm to symphysis) 
with regard to the dorsal one from the first to the thirteenth thora- 
calvertebra. I could find for the cat about the same proportion, 
given by SHERRINGTON for Macacus. 
Summary : 
I. Jn favourable cases the strychnine-segmentzone has the exact 
shape, and most likely also entirely the same extent as the theore- 
tical dermatome. It has then the shape of a trapezium, the short basis of 
which lies in the dorsal, and the long vasis in the ventral body-diameter. 
II. The strychnine-segmentzone consists of two parts which are 
sharply to be distinguished: an “inner-zone” that becomes sooner 
hyperreflectory, and. remains stronger, and an “outer-zone” that 
appears later and remains less hyperretlectory. This behaviour of the 
strychnine-zone is consequently analogous to what SHERRINGTON and 
especially W. and v. R. communicated aiready about the sensibility 
in the dermatome that they had investigated by the isolation-method. 
HI. The vulnerability of the stryclnine-segmentzone shows likewise 
great correspondence with that of the isolated root-field ; they begin 
to shrink in the ventral overlapzone, and in the caudo-ventral part 
of the zone. Moreover they offer like the root-fields the peculiarity, that 
when shrinking, the innerzone analogous to the nucleusfield, becomes 
smaller, to the advantage of the outer-zone, analogous to the border-zone. 
IV. In consequence of all this we may admit that the other pro- 
portions found for the strychnine-segmentzone, hold likewise for the 
dermatomes, that is to say: 
9 8 
the overlapping of the d.d. amounts Or and at the v.d. He By 
D 
5 
this the skin is alternately provided for: at the d.d. for er by three 
0 
roots, and for +: of each dermatome by two roots ; and at the v.d. for 
2 1 
7 by four roots, and for a of each dermatome by three roots. 
V. The “Langelaan lines” and van RIJNBERK's “excess-contrasts” by 
summation most likely answer to the strips of skin, where, at the dorsal 
diameter, the innervation takes place through three roots. If this hy po- 
thesis might be confirmed we should in the mentioned skin-stripes 
really possess a means of fixing the dermatome limits, as between 
every two such like alternating stripes, exactly a dermatome would 
be situated. 
