EXAMINATION OF SOME SPINAL NERVES 
8i 
IVth palmar interosseus muscle — it was doubtful if any degenerate libres existed in the 
nerve of this muscle in the experiment in which some were present in the nerve to extensor carpi 
radialis brevior — but in the other experiment tiiere were some undoubtedly present. 
In each of these experiments degenerate fibres existed in the cervical sympathetic — in the 
former case two fibres, in the latter five ; the degenerate fibres were small myelinate (less 
than 3.5^). 
When the motor root of this nerve has been completely destroyed by degeneration, a 
number of perfectly sound myelinate fibres are still to be foimd in the small primiir\' dorsal division 
of it, although that division supplies no cutaneous branch. The sensory fibres in this division 
must be destined for muscles, ligaments, and connective tissue endings. The motor fibres in the 
division supply the erector spina; and transvrrso-spifialrs. 
IXth Nerve or Isr Thoracic Nerve 
I. Sensory Root. Distribution to Skin. 
Example. — M. rhesus, 9 . At 9.30 a.m., the posterior roots of the Vth, Vlth, Vllth, and 
Vlllth cervical, and of the Ilnd, Ilird, and IVth thoracic nerves of right side cut in the spinal 
canal. At 6 p.m. the skin-field of the 1st thoracic was finally determined. 
' The field of response isolated is limited by a line traceable as follows : — From a point in 
the flexure of the elbow superficial to the biceps tendon, and thence down the front of the forearm 
and across the wrist a little to the radial side of the inferior radio-ulnar articulation, along the palm 
in a straight line to the cleft between middle and ring fingers, thence along the radial side of the 
ring-finger as far as the last phalanx, on the radial face of which it recurves and runs back along 
the dorsal face of the middle and proximal phalanges to the hand. On the dorsum of the hand it 
takes a fairly straight course, passes over the back of the inferior radio-ulnar joint, and climbs 
the forearm along the extensor aspect to the external condvlc of the humerus, and passes a centim. 
or more above that. The line then makes a curious and characteristic rectangular bend, winding 
round the olecranon to the inner condyle of the humerus, and then tending up the arm along the 
axillary face of the coraco-brachialis, and making for a point just below the insertion of the deltoid. 
The line, when it has nearly reached the deltoid insertion, recurves and then passes down the 
skin over the biceps to the point whence it was traced ; it thus includes a tongue-shaped area 
pointed upwards on the lower part of the flexor and axillary surface of tiie upper arm.' 
Varieties. — In one individual a little of the ulnar side of the middle finger and the whole 
of the ring-finger, and in another individual (figs. 7, 8, pp. 98, 100 in text) the whole of the 
ring and middle fingers and a piece of the ulnar side of the root of the index were included in 
the field of the 1st thoracic. This is not usual. 
This skin-field has been delimited in eight individuals — in five for the present paper, in 
three for my previous communication. 
I am inclined to think that on this skin-field, which seems a little post-fixed as compared 
with the human, rests some of the best evidence that the human brachial plexus, and therefore the 
skin and musculature of the arm of Man, are somewhat prefixed as compared with Meicacus. In 
L 
