SIGNIFICANCE OF SPINAL REFLEXES. 857 



A drop of acidulated water applied to the skin over the inner femoral 

 condyle of the frog, elicits the drawing up of the limb ; at all joints except 

 the digital, flexion occurs. The foot and digits thus sweep over the irritated 

 point of skin as though to remove the source of irritation. The opposite leg 

 is at the same time extended. If the foot of the irritated limb be amputated, 

 the stimulus evokes a movement similar to the previous, but, on account of the 

 absence of the foot, inefficient to remove the irritant. There then often 

 ensues a drawing up of the opposite limb, extension of that limb being 

 converted into flexion, and the foot of this second limb is swept over the 

 irritated area of skin ; to do this thoroughly requires some adduction. When 

 the seat of irritation is on the skin of the back, a corresponding result is 

 not infrequently obtained. The tail of a spinal animal is often abducted 

 in response to " painful " stimuli applied to its lateral surface, but it is said 

 the strychnin convulsion evoked by a similar stimulus always causes the tail 

 to move toward the side stimulated ; that is to say, if the stimulus be a painful 

 one, it is in the former case taken out of harm's way ; in the latter case 

 plunged further into injury. 



It is, of course, as impossible to disprove as to prove that psychical 

 events accompany or that they do not accompany the nervous reactions 

 of the spinal animal. To argue, as has been done, that conscious choice 

 directs reactions solely spinal, is merely to raise a question perhaps 

 interesting, but at present, and seemingly for ever, insoluble. The 

 Darwinian theory of evolution and adaptation to the environment 

 suggests how " purposive " neural mechanisms might arise. 



A well-known controversy (Pfliiger, Lotze) as to the psychical powers 

 of the cord, occurred prior to the advent of the Darwinian theory. 

 Long previously, Prochaska had written: "The general condition which 

 dominates the reflexion from sensorial impressions (i.e. those affecting his 

 sensorium commune) to motor nerves is the instinct of the preservation of 

 the individual." For "the individual" Grainger substituted "the organ." 

 Lotze's position may be illustrated by the following quotation : — " The using 

 of the limbs, in so far as the local direction of them goes, is no independent 

 and self-completed labour of the will, but only the employment of an already 

 present mechanism, the action of which the mind merely wills to go or not 

 to go, but by no manner of means can regulate in all its details. We find 

 arranged and interconnected in groups combined movements serving to protect 

 the organism from harm, and in these the tendency to action in response to 

 stimuli is so strong, that in many cases the mind cannot suppress the tendency 

 even by the willing of antagonistic movement, e.g. coughing, sneezing. In 

 fact, how ill were it for our bodily welfare, in many circumstances, did its 

 defence depend on intellectual decision instead of on a mere machine." 



As to the interpretation of the " purpose " of spinal reflex movements, it is 

 more difficult than with higher reflexes, because the movements are often of 

 more limited extent. The wider the field of a combined movement — if not 

 convulsive but co-ordinate — the less dubiously does it indicate its object. But 

 there is at best much room for fancy, and great caution is required. The spinal 

 reflex " drawing up " of the limb that forms the usual response to a moderate 

 stimulus to the foot, is generally and can be with plausibility construed as 

 an effort to lift the irritated foot out of the way of harm. The stimulus is 

 indeed usually of an intensity sufficient, were the cerebro-spinal system intact, 

 to cause sensation of unpleasant quality. But it is possible to interpret this 

 reflex as the local part of a larger reflex of progression. That alternative obtains 

 support from the usually concomitant reflex extension of the fellow-limb of the 

 opposite side. Further, the drawing up and protraction of the stimulated leg 

 is usually succeeded by its extension, namely, by the phase of movement that 





