68 
THOMPSON YATES LABORATORIES REPORT 
Ventral Primary Division of IInd Cervical Nerve 
When the dorsal primary division of the nerve has been severed at its origin from the 
trunk of the entire nerve, the change produced in the shape and extent of the skin-field is that 
instead of the field reaching the mid-dorsal line it stops short some centimetres above the root of 
the ear. The point where it stops short is about one-third of the way from the upper border of 
the root of the ear to the middle line of the scalp. The field is thus separated from the mid- 
dorsal line by a not very wide gap, and the lateral boundary of the gap is a line which runs 
parallel with the mid-dorsal. This line is the dorsal border of the skin-field of the ventral 
primary division of the nerve, and it joins the anterior and posterior borders of the skin-field at 
angles which approach very closely indeed to right angles. The skin-field of the ventral primary 
division covers quite four-fifths of the skin-field of the entire nerve. 
Motor Distribution. 
I have examined the distribution of the motor-root of the IInd cervical nerve by 
mechanical and faradic excitation, and by faradic excitation of the separate dorsal and ventral 
divisions, in four individuals. My results are as follows, and showed no marked individual 
variation. 
Dorsal Primary Division. — Cervicalis ascendens, trapezius, complexus, splenius, inferior 
obliquus, trachelo-mastoideus. 
Ventral Primary Division. — Longus colli, sterno-mastoideus, rectus anticus major. Infra- 
hyoid muscles, viz., omo-hyoideus (chiefly posterior belly), genio-hyoideus, sterno-hyoideus, 
sterno-thyroideus, thyro-hyoideus. 
IIIrd Cervical Nerve (Figs. 4, 5, and 6) 
The anterior border of this skin-field has been observed in two individuals, the posterior 
border in six individuals. 
Anterior Border. 
Example. — M. rhesus, young 9 . The Vth cranial and the IInd cervical nerves cut inside 
the dura mater at 10.30 a.m. Final examination of the upper edge of the field of the IIIrd at 
5.30 p.m. 
' The upper edge of the field of response starts from the mid-dorsal line on the scalp at a 
point about i centim. behind halfway between the bregma and the lambda ; it runs down to the 
back of the root of the pinna about 5 centims. from the top of the root ; it turns over the upper 
edge of the pinna not far from the root, and then descends on the helix and in front of the tragus 
to reach the outer face of the vertical ramus of the lower jaw ; along this it descends parallel with 
and slightly in front of the posterior edge of the ramus. It then bends forward in front of 
the angle of the jaw and slopes down the horizontal ramus of it to leave its lower edge and reach 
the mid-ventral line distinctly above the thyroid cartilage.' 
