84 THOMPSON YATES LABORATORIES REPORT 
overlooked it altogether in Dog and Monkey. Ferrier and Yeo (1884) were the first to 
demonstrate that it contributes to the hand : they describe it as supplying the interossei and 
evoking ' interosseous flexion.' In my own paper I noted instances in which it evoked flexion 
and pronation at wrist, as well as full flexion of the thumb and fingers, both in M. rhesus and in 
sin'icus ; also in Cercoplthecus and in Cynocephalus, I have also seen slight flexion of the wrist as a 
willed movement in a Macaque in which the Vlth, Vllth and Vlllth cervical and 1st thoracic 
roots had been cut through. In fact, it supplies flexor profundus, flexor sublimis, palmaris longus, 
pronator quadratus, as well as the n u les of the hand. 
In all cases the scaleni (not mcdius) muscles contained degenerated nerve-fibres ; as also, 
via the posterior primary division of the nerve, the erector spina and transverso-spinales. 
Examined by the degeneration method and the teasing of muscle-nerves for detection of 
breaking down nerve fibres, the following results were obtained in two Macaques : — 
Experimoit i. 
palmaris longus. 
pronator quadratus. 
flexor longus poUicis. 
flexor sublimis digitorum. 
flexor profundus digitorum. 
deep short muscles of thumb. 
all the lumbricales. 
all the dorsal j 
\ interossei. 
all the palmar ) 
short muscles of little finijer. 
Experiment 2. 
flexor longus poUicis. 
flexor sublimis digitorum. 
flexor profundus digitorum. 
deep short muscles of thumb, 
short muscles of little finger, 
all the lumbricales. 
all the dorsal ^ 
interossei. 
all the palmar J 
The fact that after degeneration ot the lowest four cervical and of the 1st thoracic nerves, 
excitation of the Ilnd thoracic or of the cords of brachial plexus still evokes a flexion of the wrist 
and of the digits, in which the terminal phalanges of the latter are flexed on the middle phalanges 
as well as these last on the proximal, might be taken to prove that the flexor profundus digitorum 
was in action, and therefore innervated by the Ilnd thoracic. The flexor profundus is, it is true, 
usually innervated in part by the Ilnd thoracic, but the above fact is not the proof of it. In Man 
the flexor profundus (perforans) is the flexor of the terminal phalanges on the middle phalanges, 
and the sublimis does not flex the former. In the Macaque both profundus and sublimis flex 
similarly the terminal and middle and proximal phalanges ; if the middle phalanges are prevented 
from flexion (as presumably under action of the interossei and lumbricales), the sublimis cannot 
flex the terminal phalanx, although the profundus can. This action can be easily examined by 
pulling on the respective tendons in the Macaque. 
In all the Macaques I have examined in reference to the point, the Ilnd thoracic 
innervates the hand not only via the ulnar nerve, but also via the median. Hepburn has 
described that in Monkeys the ulnar gives a considerable branch to the median in the upper part 
of the forearm. It is through this that the above-described distribution takes place. Although 
