266 NATURE AND MAN. 



the arguments on the other side being rather of the nature of 

 cumulative probabilities. Thus (i) as the separated head of the 

 frog will itself show reflex action (the eyelid closing when its edge 

 is irritated), the division of the head from the body would establish 

 two distinct centres of consciousness, or two fgos, if the per 

 formance of reflex action be accepted per se as an indication of 

 the persistence of sensibility ; while (2) the number of these 

 centres may be further multiplied by dividing the spinal cord in 

 the middle of the back, so that the reflex actions of the fore limbs 

 are performed through the instrumentality of the anterior segment, 

 and those of the hind limbs through the instrumentality of the 

 posterior segment ; and (3) cases are of no infrequent occurrence 

 in the human subject, in which, the lower segment of the spinal 

 cord having been entirely cut off by disease or accident from 

 communication with the brain, reflex actions in the legs may be 

 excited by tickling the soles of the feet, or the application to 

 them of a heated plate, without the least consciousness on the 

 part of the patient, either of the application of the excitant, or of 

 the respondent motions it calls forth. And though it was at first 

 urged that this last fact gives no assurance that the endowments 

 of the spinal cord are the same in the frog as they are in man, yet 

 there has been a growing disposition to recognize the uniformity 

 of Nature in this and other particulars, and to accept the facts of 

 human consciousness (or unconsciousness) as affording the best 

 data for the interpretation of such actions of the lower animals as 

 are performed through a demonstrably similar instrumentality. 



When once this principle is admitted, it becomes obvious that, 

 however &quot; purposive &quot; may be the character of such actions, their 

 performance from the first, without training or experience, may be 

 regarded as valid evidence that they are determined by nothing 

 else than a physical mechanism. No one doubts this in regard to 

 that rhythmical succession of contractions and dilatations of the 

 auricles and ventricles of the heart, by which the circulation of 

 the blood is kept up ; nor in regard to that regular sequence of 

 respiratory movements which serves to maintain the aeration of the 

 blood, alike in the waking state while the attention is completely 

 engrossed elsewhere, and in the states of profound sleep and 

 insensibility. And there are no co-ordinated muscular move 



