EXAMINATION OF SOME SPINAL NERVES 163 
That is to say, the flexors of the knee, so inaccessible, as stated above (pp. 145-146), to the local 
idio-lateral excitation, are delicately sensitive to contra-lateral. The same result often follows 
electric excitation of either of the plantar nerves, of the cutaneous division of musculo-cutaneous 
nerve, and of the popliteal and hamstring nerves themselves, i.e., idio-lateral flexion of knee, 
contra-lateral extension of knee. Sometimes bilateral flexion is obtained, and in the Rabbit, in my 
experience, crossed flexion instead of crossed extension is the rule. 
Again, excitation of Vlth and of Vllth post-thoracic roots evokes flexion of idio-lateral 
knee, hip, and ankle, but extensioh of contra-lateral knee. Excitation of the perineal skin I have 
seen give the same. In this reflex there is produced on the crossed side not only excitation of the 
extensor muscles, but inhibition of their antagonists. In Dog and Cat, when the flexion of one hip 
and knee, e.g., right, has been evoked and is in progress, contra-lateral excitation appropriately 
timed often relaxes the contracted flexors of the right limb. Similarly, when after ablation of the 
hemispheres (Cat, Rabbit), the extensor tonus, which I termed above, p. 150, decerebrate rigidity, 
has set in, excitation of the hind-foot of one side inhibits the contraction of the same side 
extensors of knee, but increases the contraction of the extensors of the opposite knee. And in tlie 
same way, at elbow, the triceps of the crossed side is increased in its contraction, while triceps of 
the same side elbow is inhibited even to the extent of reaching its post-mortem length. Graphic 
records show that with the contraction of triceps occurs active relaxation of biceps ; with the 
contraction of biceps occurs active relaxation of triceps, and similarly with the antagonistic muscles 
of the knee-joint. Similarly, excitation of the side of the superior vermis or funiculus cuneatus 
{e.g., at calamus scriptorius) causes, during the state of decerebrate rigidity, relaxation of the same 
side triceps brachii with contraction of the same side flexors of elbow, and at the same time still 
further relaxation in the opposite biceps and increase of contraction in the opposite triceps. The 
case of the antagonistic muscles at knee-joint I have similarly examined from sup. vermis and f. 
gracilis with similar result, except in Rabbit, where flexion of both knees seems the rule. 
In a Monkey with mid-thoracic spinal transection, in the course of months flexion of hip as a crossed 
reflex developed. It was much easier to obtain this in one limb than in the other, and was obtained 
more readily as an idio-lateral reflex on that side on which it was the easier as a contra-lateral reflex. 
Late rigidity affects in the Monkey flexors of hip ; I do not therefore lay stress on this instance, but it 
deserves mention. 
The asymmetry of the crossed reflexes of the legs is important because obviously coji- 
nected with the co-ordination of progression. 
The idio-lateral flexion reflex is prepotent and inhibits the crossed extension, e.g., stimulation 
of both feet together causes drawing up of both, so also at elbows. Semisection above the lesion 
makes the crossed reflex more easily evoked from the side of the semisection. Splitting length- 
wise, from top of Vth lumbar to bottom of Vllth, destroys the crossed, but not the idio-lateral. 
Again, contra-lateral flexion is apt to accompany idio-lateral flexion when the stimulation is strong. 
In the Monkey the idio-lateral flexion of hallux, knee, and hip, excited by an excitation of 
the foot, is often followed in the opposite hind-limb by adduction of thigh. In the same animal 
dorso-flexion of the ankle elicited from the Vllth (aflferent) post-thoracic root is often followed by 
