858 THE SPINAL CORD. 



would normally succeed flexion in the performance of progression. Again, in 

 examining the instances adduced to illustrate the supposed purposive protective 

 movement, resulting in removal of an irritant from the skin, it must be 

 remembered that the flexion of hip, knee, and ankle in the frog is the regular 

 primary response to stimulation almost anywhere in the skin of the limb or 

 loin. And the same movement is seen, when the spinal preparation is 

 altogether deprived of skin ; also when the afferent roots to the limb are 

 severed, the stimulus being applied to the skin of the loin. The alternative 

 movement (flexion of the contralateral leg) ensuing when the primary move- 

 ment of reaction has been performed — that it has been performed uselessly 

 may be only of influence in so far as it means prolongation of the stimulus — 

 may be simply the second phase of the spinal reflex, which always tends 

 to be of alternating character, especially when a stimulus is prolonged. 

 Besides, it must be granted that the ablation of the foot, or the pressure 

 necessary to- restrain it if not ablated, is in itself an additional stimulus. A 

 suggestive context to the experiments of so-called " spinal choice " is furnished 

 by the revival to action of a phrenic nucleus, after being thrown out of action 

 by severance from its own half of the bulbar centre. Severance of the contra- 

 lateral phrenic nerve then brings it into action again. 1 



Considered in the light of the Darwinian theory, the normal con- 

 nections between any afferent path {e.g. from a piece of skin), and the 

 motor apparatus conjoined with it, can only be such as to lead to a 

 purposive movement. The whole ground of " purpose " is speculative. 

 The physiologist can only state that the " spinal " animal exhibits 

 visceral digestive reflexes, performs excretory and sexual functions, 

 executes a number of movements preservative of the cutaneous 

 sensorial surface, and in simpler animal types shows maintenance of 

 habitual posture and movements preparatory for and partly executive 

 of progression. The inclusion of the bulb with the spinal cord does not 

 in this respect essentially alter the statement. More actions in which 

 the skeletal musculature is co-ordinated immediately with and for the 

 service of visceral organs are added, such as the taking of food, including 

 oxygen, the out-putting of the pulmonary excretion, and the regulation 

 of the activity of heart and blood vessels. But of any further reaction 

 toward defence or self-preservation than is already included by implica- 

 tion in the above essentially visceral reactions, there is scanty evidence. 

 Perhaps hunger and thirst, so far as certain subconscious nervous 

 conditions pertain to them, may be present, but, as far as is observable, 

 they initiate no movement ; that is, in the spinal and in the bulbo-spinal 

 animal the skeletal musculature as a motile mechanism lies still beyond 

 their reach. Grainger's conclusion 2 was that spinal cutaneous reflex 

 movements "are either of a preservative character, or resembling 

 the motions which the function of the organ requires." From the skin 

 of the spinal creature, reflex movements resembling those executed by 

 the normal individual in "preening" or cleansing itself, are of wide- 

 spread occurrence. Together with the " preening " actions of the 

 " spinal " fly, grasshopper, astacus, etc., there fall into this category the 

 movements by which the " spinal " frog wipes irritants from its back 

 and face ; the " nettoyage " by the tortoise, the posturing of the hind- 

 limbs and tail of the " spinal " dog concurrently with reflex evacuation 

 of the faeces, tending to keep the body from being soiled, and the 

 " scratching " and " shaking " reflexes of the spinal dog. All these are 



1 W. T. Porter, Journ. Physiol., Cambridge and London, 1895, vol. xvii. p. 455. 



2 "Functions of the Spinal Cord," London, 1837. 



