1142 
The lines 5 and 7 constitute 
in the same way the posterior 
boundaries of thoracalis 10 and 
9. The scheme of fig. 6 is to 
represent this dermatome with 
the coverings. The anterior 
boundaries of thoracalis 13 and 
12 and the posterior boundaries 
of 10 and 9 are indicated by 
the ordinal figure of these 
Ai ; 7 ol dermatomes. 
k § f Now we find, that the der- 
Hig. 6. matome-part ¢, e, d, is covered 
(Dermatome of Thoracalis 11). by 13 and 12, likewise 6, 4, / 
by 10 and 12 a,h,k by 9 and 
10. These 3 strips are consequently innerved along three hind-roots. 
Between those are two strips of innervation by 2 hind-roots. 
We found with the dermatome of thoracalis 12 equal relations. 
A dermatome of the thoracal region contains consequently 3 strips 
that are innerved along three hind-roots. Two of these are found at 
the edges, whilst the third is on the centre of the dermatome. 
The number of strips that are innerved by 3 hind-roots is however 
equal to the number of dermatomes, for each of the covering strips 
of 3 fields lies on the centre of a dermatome, but likewise at the 
edges of two adjoining dermatomes. So the strip 6,9, /, that is 
innerved from the hind-roots 10. 11, and 12, in the centre of root- 
field 11, at the anterior edge of field 12 and at the posterior edge 
of field 10. 
The dermatomes determined here have most likely not appeared 
completely at the ventral side. At least I did not find here anywhere 
4 dermatomes covering each other. Often the strychnine-fields are less 
sharp and distinct at the ventral side. In many other determinations I did 
find this covering of + fields ventrally. If this had here also been 
the case, c,e would have cut the line 6,7 and g, 6 the line a, h. 
Before I had found the method of determining the covering of 
the root-fields described above, I had already reflected on another 
method which has only a theoretical value. If namely the skin is 
irritated on a definite spot, action-currents must flow to the central 
nervous system along more than one hind-root, in case there is 
covering. Now we ought to registrate these action-currents by means 
of two string galvanometers. If now, when irritating on one definite 
spot, we can deduct action-currents from 2 successive hind-roots, 
