EXAMINATION OF SOME SPINAL NERVES 
i6i 
Observations on the knee-jerk indicate* that, in the neighbourhood of a spinal transection, the 
short local reflex path and neuron may, although peculiarly free for and responsive to changes occur- 
ring in that short local path, be all the less open to and receptive for impulses approaching by other 
channels more distant and less local. The local reflex arc might, so to say, be so preoccupied in 
the business of its own local, and no doubt primary, circuit as to be deaf to reverberations of 
explosive changes at a distance. Excitation of skin of neck or pinna frequently spreads down 
the cord, and produces movement in tail or in hind-limbs without evoking a twitch in either fore- 
limb ; but, as stated above, fore-limb itself can easily be provoked to movement by excitation at 
the same source on other occasions. That is to say, the downward impulses not unfrequently 
skip the motor neurons of arm to go to those further down. A point emphasized by the 
experiments is, that in the chain of spinal centres, the long paths of association connecting 
different levels are primarily uncrossed. 
This appears to hold not only for the numerous instances of descendant direction, but also 
for the scanty ones of ascendant direction. Crossed conduction, on the other hand, seems to exist 
mainly between segments of not widely different segmental level. Noteworthy is the observation 
that extension at hip, knee, and ankle is generally characteristic of the crossed reflex ; also that, 
when a movement is evoked in both hind-limbs by unilateral excitation applied at a distance, e.g., 
at one pinna, the movement is usually the same in kind in both hind-limbs — e.g., flexion of digits 
of both feet, extension of both hips, flexion of both knees — -but is always the more extensive and 
powerful in the idio-lateral limb. Similarly, in the case of the fore-limbs, the bilateral movement 
evoked in them by excitation at a distance, i.e., in some other spinal region, tends to be of 
symmetrical character. I.e., extension of both elbows, &c. 
A remarkable phenomenon of constant occurrence, which illustrates the tendency of 
impulses to keep to the same side of the cord for considerable distances, is one which may for that 
reason be introduced here, although its explanation is not easy, and can only be offered after 
further experimentation. Application of fine electrodes to, or stabbing with a minute needle of, 
Goll's column at the extreme top of the cervical region, and also lower down, evokes movement 
in the hind-limb of the same side : this movement is nearly always in Macacus flexion of digits, 
in the Cat often flexion of knee. Movement of the thumb and fingers of the hand can be evoked 
by similar excitation of Burdach's column, always the hand on the same side only as the column 
excited. The movement is still perfectly obtained after transection of the cord just above the 
point of excitation. It is cut out by transection of posterior column alone at various levels below 
the site of excitation. Anal movements are freely obtainable in this way from column of Gou. 
at the very top of the cord. The lateral columns of the cord, curiously enough, do not seem 
necessary to these movements, and I obtained them in one instance in which I had a pyramidal 
tract on one side hugely degenerated after ablation (in Monkey) of the whole Rolandic region. 
Yet the movements were at least as well obtained from the left (degenerated) side as from the 
right. A phenomenon that may be mentioned in this connection as also employing uncrossed 
* Sherrington, ' Proc. Roy. Soc.,' vol. 52, 1892. 
V 
