EXAMINATION OF SOME SPINAL NERVES 
73 
VIth Cervical Nerve. (Figs. 4 atid 5 in text, pp. 64, 65) 
I. St'Nsory Root. 
This skin-field has been delimited completely in tour individuals, and incompleteh' in two 
more. 
Example. — M. rhesus. 9, \ oung. At 9 a.m. the posterior roots of the Ilird, IVth, Vth, 
Vllth and Vlllth cervical, and of the 1st, Ilnd and Ilird thoracic nerves were severed in the 
vertebral canal. The isolated field of response, due to the intact VIth cervical root, was finally 
delimited about 5 p.m. 
'The field of response is limited by a line which starts from a point on the infraspinous 
fossa of the scapula near the edge of the deltoid muscle. The line crosses the lateral part of the 
infraspinous fossa obliquely and turns down tlie arm behind the posterior border of the deltoid 
muscle. It descends the arm lengthwise, well on the triceps side of the furrow, between the 
masses of the extensors and flexors of the elbow. It enters the forearm close behind the outer 
condyle, and thence passes in an almost straight line to reach the radial side of the index finger, 
where on the proximal phalanx it recurves. The line returns across the palm to tiie forearm over 
about the middle of the thenar eminence ; it crosses the wrist on the radial side of the lower 
radio-ulnar joint. On the flexor aspect of the forearm it ascends close to the ulnar side of the 
prominence made by the supinators of the wrist and long extensors of the fingers. It crosses the 
flexure of the elbow about the middle of it, and climbs the prominence over the flexors of the 
elbow somewhat to the ulnar side of the middle line of the biceps. Close above the junction of 
the limb with the tnmk the line turns outward and downward, and sweeping below and round 
the deltoid muscle reaches the spot on the infraspinous fossa whence it was traced.' 
Variation : — 
In the first experiment the field traced was closely similar to the above ; in a third experi- 
ment it did not appear to extend lower than the styloid process of the radius, and I convinced 
myself it did not include the thumb, for the observation was repeated many times in the course of 
24 days. When the animal was finally examined, electrical excitation of the central end of the 
musculo-cutaneous nerve, about three inches below the elbow, elicited smart reflexes. In a fourth 
individual nearly the whole length of the radial side of the index finger was included in the field. 
There must, therefore, be a considerable degree of variation in the extent to which this 
nerve contributes to the sensation of the skin of the hand. The thumb, and even one half of 
the index finger, in some individuals, enter into the composition of the field, but in some 
they do not. 
2. Motor Root. VIth cervical. [See Conspectus, p. 114 infra.) 
Three experiments, all on Macacus rhesus., by the combined degeneration and excitation 
method as explained above (pp. 51, 52). 
K 
