136 THOMPSON YATES LABORATORIES REPORT 
tips of the hands and feet. Further, the fundamental distinction between the condition and that 
induced by any chemical nervous depressant, is clear in the following two features, (i) The 
spinal motor neurons, though profoundly inaccessible to stimuli, applied via skin or afferent nerve- 
trunks, are perfectly open to any applied via the pyramidal paths : excitation of the pyramidal 
tract at the top of the cord evokes as readily as or more readily than ever, in both limbs, its usual 
variety of movements. (2) Excitation, mechanical or by weak electric currents quite 
imperceptible to the tongue, of the centra/ ends of the spinal posterior ( dorsal^ sensory ) roots themselves, 
fairly readily evokes the usual reflex movements elicitable — although enormously stronger stimuli fail 
absolutely when applied to the skin and afferent nerve-trunks. At first finding this, I supposed an 
explanation might lie in the fact that the roots contain large numbers of afferent fibres from 
muscles,* while the peripheral nerve-trunks and surfaces tried are chiefly cutaneous ; but 
excitation of the spinal end of the hamstring-nerve, with its quantities of afferent nerve-fibres from 
muscle and deep structures, caused no more effect ; caused, in fact, less effect than a pure 
cutaneous sensory trunk, such as the long saphenous. This condition, although most usual and 
striking in the Monkey, and therefore here chiefly described in his case, is seen, to a certain extent, 
also in Cat and Dog. When, in them, the spinal depression is great, it is easily found to be more 
marked when examined by excitation of skin or peripheral nerves, than when examined by 
excitation of the afferent spinal roots ; the motor reactions provokable from the former, are less 
ample and less numerous than from the latter. It is no question of escape of exciting current to 
the motor roots themselves. Finally, this further point seems clear, from the above analysis of 
' shock,' that the phenomenon is not resident, chiefly or indeed at all, in the peripheral sensory 
end-organs, or at their junctions with afferent neurons ; because the peripheral nerve-trunks 
themselves are as inefficient as the skin, tendons, &c. My own experience leads me to think that 
the condition of a spinal cord isolated by a spinal transection is often more normal a few hours 
after the transection than it is when long periods of weeks and months are allowed to elapse. I 
am well aware that this is contrary to the opinion of Goltz and others. The advantage believed 
to accme from waiting is that the phenomena of shock may have time to pass off as completely as 
possible. How long the phenomena of shock may last at longest is a question on which very 
different views are held. Goltz, to whose trenchant observations and bold system of experiment 
we owe so much of our knowledge of the physiology of the central nervous system, is the founder 
of a school which works in the belief that the phenomenon of shock may persist for months, even 
years. It is, as far as not, merely a matter of nomenclature, a question on which no definite 
decision seems as yet possible. I myself have gradually been driven to the belief that * shock ' 
does not take long to pass off, i.e., does not at longest persist for more than a few days.t But 
though shock passes off, the alterations produced in the isolated cord or piece of cord (by 
permanent withdrawal of the influences it has lived accustomed to receive from other portions of 
* Sherrington, ' On the Anatomical Constitution of the Nerves of Skeletal Muscles,' ' Journ. of Physiol.,' vol. 17, 1894. 
t I am not considering here the complications arising out of long, badly healing and suppurative Ufounds, and the 
continual irritation they may produce if situate in the nervous system. Such conditions no longer, thanks to Lister, complicate 
the lesions of experimental physiology. 
