70 THOMPSON YATES LABORATORIES REPORT 
centim.) behind the root of the pinna. It runs about .5 centim. behind the vertical ramus of the 
jaw and meets the mid-ventral line on the neck at the level of the cricoid cartilage, or a little 
above that.' 
Posterior Border. 
Example, — M. rhesus. <J, very young. At 10 a.m. the posterior roots of the Vth, Vlth, 
Vllth cervical, and of the 1st, Ilnd, Ilird, IVth, and Vth thoracic nerves of the right side severed. 
At 4.30 p.m. examination of the skin-fields completed. 
' The upper field of response (IVth cervical) is bounded below by a line which starts from 
the mid-dorsal line of the body, about on a level with the upper end of the vertebral border of the 
scapula, and from these slopes down to meet the vertebral border at the root of the spinous process. 
Thence the line slopes down on tlie infra-spinous fossa, and recurves upward again, passing over 
the axillary border of the scapula, midway between the acromion process and the inferior angle. 
It then descends the arm below the prominence caused by the deltoid muscle, and passes down the 
outer face of the arm in the groove between the muscular masses of the triceps and the flexors of 
the elbow. The line finally reaches a point as far as midway, or rather below midway, between 
the tip of the acromion and the angle of flexure of the elbow. From this point the line turns 
abruptly inward over the biceps, and, in so doing, recurves slightly toward the top of the shoulder. 
Before quite reaching the middle of the anterior surface of the biceps it slopes downward again 
and reaches a point on the inner aspect of the prominence caused by that muscle, and nearly three- 
quarters down the arm. Thence it turns upward again on the coraco-brachialis, and runs under 
the pectoral fold and then winds over the edge of that fold to attain the ventral crossed overlap of 
the skin-fields of the left side at a point about 1.5 centims. above the nipple, and just below the 
3rd costal cartilage. 
' The ventral crossed overlap is a full centim.' 
Motor Distribution. 
Examined in four individuals. 
The dorsal priinary division supplied :- -Complexus, splenius, trachelo-mastoideus, cervicalis 
ascendens, transverso-spinales. 
The ventral primary division supplied : — Levator scapula?, longus colli, levator claviculae, 
scalenus medius, trapezius subclavius. In three individuals the front, especially sternal, portion of 
the diaphragm. In one experiment this was examined by degeneration ; the degeneration in the 
ventral division of the phrenic nerve on the diaphragm was much heavier than in the dorsal 
division. 
Vth Cervical Nerve (Figs. 4 and 5) 
I. Sensory Root. 
The anterior border of the skin-field of this nerve has been delimited in two experiments ; 
the posterior border in three experiments. In three individuals the entire field has been 
completely delimited. 
Anterior border : — 
Example. M. rhesus^ $, young. At 11 a.m. the 1st, Ilnd, IlIrd, and IVth cervical 
