EXAMINATION OF SOME SPINAL NERVES 
91 
III. In the case of the Vlth post-thoracic nerve of Mucacus and of the Vllth of the 
Cat, the discrepancy between sensory distribution, as examined in skin, and motor distribution, 
as examined in skeletal muscle, reaches its extremest degree ; yet even there the sensory root 
supplies nerve-fibres to the same muscles which the motor root supplies. 
Example. — M. sinicus : the motor and sensory roots, including the whole spinal ganglion of the 
right Ilird, IVth, Vth, Vllth, and Vlllth post-thoracic nerves excised ; the mo^or and sensory roots of 
the Vlth post thoracic simply severed well proximal to the ganglion. Thirty-five days' interval allowed 
for degeneration ; the animal then finally examined, and its nerves prepared. 
The lumbo-sacral plexus proved, on dissection, to be of prefixed type. 
On excitation of the motor root of the Vlth nerve of the intact side, contraction was noted in the 
following muscles : tibialis anticus, extensor longus digitorum, peronei, tibialis posticus, flexor longus 
digitorum, gastrocnemius, extensor brevis digitorum, flexor brevis digitorum, semimembranosus, semi- 
tendinosus, biceps, pyriformis, muscles of the back abducting the root ot the tail. 
The following nerves of muscles were microtomed for detection of some fibres ; in most cases they 
were examined by teasing also : — 
Nerve-trunk. 
n. to tibialis anticus and extensor longus 
n. to peroneus longus 
n. to extensor brevis digitorum 
n. to tibialis posticus 
n. to fiexor brevis min. digiti 
n. to gastrocnemius, mesial head 
„ „ lateral „ 
n. to semimembranosus 
n. to semitendinosus 
n. to biceps .... 
n. to all the hamstring group — 14 bunales 
Vlth post-thoracic nerve, including spinal ganglion and | 
ventral and dorsal primary divisions of the nerve . | 
collateral cutaneous nerves of the toes — 
2nd toe, mesial side, dorsal twig 
,, lateral side, dorsal twig 
„ „ „ ventral twig 
cleft between 3rd and 4th toes, dorsal twig 
„ „ 4th and 4th toes, dorsal twig 
5 th toe, lateral edge, dorsal twig 
„ „ „ ventral twig 
Number of sound myelinate fibres. 
hardly any. 
hardly any. 
a few sound fibres. 
few, but more than to tibialis anticus. 
a fair number. 
a large number of sound fibres, 
a large number of sound fibres, 
a few sound fibres, 
a large number of sound fibres, 
a great number. 
no bundle without sound fibres. 
the number of fibres in the ventral 
division must be more than halt, 
and in the dorsal very nearly halt. 
five fibres, 
seventeen fibres, 
about sixty fibres, 
plenty. 
at least a half are sound, 
more than half are sound, 
more than half are sound. 
Example. — Cat : the motor and sensory roots of the Vth, Vlth and Vlllth post-thoracic nerves 
excised, including the whole ganglion of each sensory root. The Vllth post-thoracic severed well on the 
spinal side of the ganglion. Time allowed for degeneration, forty-three days. The animal then finally 
examined, and the various nerves prepared. The lumbo-sacral plexus was found by dissection to be a 
moderate example of the prefixed class. The Vllth post-thoracic nerve contributed no twig to the 
obturator trunk. Excitation of the IXth post-thoracic root gave no contraction of the limb muscles. 
The cutaneous distribution of the Vllth post-thoracic nerve in the Cat includes the foot both 
dorsal and plantar aspects, and the lateral aspect of the leg below the knee, reaching above the knee for a 
short distance only on the postero-lateral surface of the limb. On excitation of the motor root of this 
nerve on the side of the body in which it was intact, contractions were noted in the following muscles, 
tibialis anticus, peroneus, tibialis posticus, flexor longus digitorum, gastrocnemius, semimembranosus, 
semitendinosus, biceps, and in muscles of the back moving the root of the tail. Of the muscular ray thus 
innervated by the motor root of this nerve the distal part only is, therefore, covered by the skin innervated 
