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sible zone on the extremity). The line then continues downward along the 

 sternum until beyond the 4t[^ rib, takes again a turn upward, and bending 

 cranially it ends in a point near the extremity of the spina scapulae. 

 Caudally there is found no insensible dorsal portion. 



Near to the angulus scapulae, the line turns back again on the dorsal 

 surface of the upper arm, straight in the direction of the olecranon, 2 cm. 

 before reaching this, it takes a bend towards the ventral surface of the upper- 

 arm, and crossing this, returns to the ventral portion. It is separated by 

 a narrow zone from the sensible ventral triangle. (On the skin it passes 

 here into the caudal boundary-line of the sensible ventral triangle). Above 

 the latter it takes a turn in dorsal direction, and having reached again the 

 dorsal surface on the middle of the upper-arm, it makes straight for the 

 back, reaching this at the ö^^^ vertebra. 



Moreover there is found an insensible spot on the lower part of the extremity. 



This has its beginning a little under the epicondylus humeri lateralis, 

 it crosses longitudinally, the backside of the fore-arm likewise the hand and 

 passes along the ulnar margin on to the plant, crosses along side the plants of 

 the fingers which are insensible, and continues, taking a rectangular bend before 

 the plant of the 4*1^ finger, straight upward towards the epicondylus lateralis. 



It is allowed to draw a few conclusions from these experiments. 



1st The caudal portions of those derniatomata, bounding the 

 extremity caudally, especially of the 10^^' and the 11^'', are pushed 

 over the lower situated derniatomata. 



We have observed already previously that, cranially of the 15''^ 

 dermatoma, the cutting through of at least three adjoining roots is 

 necessary, in order to obtain insensible dorsal spots. Only wdien 4 

 adjoining roots are cut through, a continuous insensible zone is found 

 in that region. This presents a marked difference with the conditions 

 existing on the trunk, wdiere for the same purpose, the cutting through 

 of two, resp. three roots, suffices. 



This fact is contlrmed here. By cutting through the 12''', 13^'' 

 and I4"i root (tig. I) or the Jl^'', 12^^' and 13''i root (fig. II), anal- 

 getic areas are called into existence both dorsally and ventrally, 

 but no continuous zones; when cutting through the 10^'', TJ'^ and 

 12''i root (fig. VI), the analgetic dorsal area fails even, though the 

 lO^, ll^'i and 12"' dermatoma possess each of them a dorsal 

 portion, which it is possible to isolate. 



The significance of this fact is evident. The growth of the extre- 

 mity in caudal direction, removes the caudal boundaries of the 10''' 

 and 11"' dermatoma towards the caudal side. In the lateral part the 

 10"' dermatoma overlaps the 14''', the II"' the 15"'. The dorsal pieces 

 of the 10"', 11"' and 12"^ dermatoma are lying so near to one 

 another or even covering one another, that the unimpaired 6"', 9"^^ 

 and 13"' are able to proN'ide together for the sensory innervation 



27^^ 



