104 THOMPSON YATES LABORATORIES REPORT 
arm. After the section of these nerves, the field of remaining jesthesia on the dorsum of the 
hand is that shown in fig, 12 by the dotted line along the middle of back of the hand and the 
dotted lines on the poUex and and and 3rd digits. If the dorsal branch of the ulnar be then 
severed, the field of aesthesia is further reduced, and confined by the dotted lines on the annulus 
and minimus as on the three radial digits. On the palm, section of the median nerve in the fore- 
arm produces a patch of anaesthesia, the limits of which are shown in fig. 11 by the line 'ulnar.' 
Section of the ulnar trunk halfway down the forearm produces a patch of anassthesia with the 
limit marked by the line 'median' in the figure. 
Fig. 12 
Dorsal ulnar field. 
Median. Median. Median. 
In harmony with the difference of overlap of territories of the palmar nerves and of their 
spinal roots, is the much greater overlapping of the contiguous borders of the Vth cranial and Ilnd 
cervical than of the territories of the individual divisions of the Vth cranial itself (see above, 
p. 62), a difference which was made use of in determining whether those divisions were of seg- 
mental quality, or, like other peripheral nerves, functional rather than morphological entities. 
It is then clear that in the hand, as in the foot of Macacus, the extent of overlap of the 
skin-fields of the peripheral nerve-trunks, even on the exquisitely sensitive plantar and palmar 
surfaces, is much less than that of the cutaneous areas of the nerve-roots ; it is, in fact, not so 
