SPECIAL PHYSIOLOGY. 53 



say, by means of the symmetrical nerves (law of symmetry) ; 

 and this corresponding extremity (left, in the example select- 

 ed) presents always movements less intense than that (right) 

 which received the excitation (law of intensity). Finally, if 

 the excitation still increases, the motory reaction is extended 

 to the centrifugal fibres of a different height, but always ad- 

 vancing towards a higher (or anterior) portion of the spinal 

 cord, that is to say, that the radiation extends from below 

 upwards, from the spinal cord to the encephalic cord (bulb, 

 pro.tuberance, etc.), (law of radiation) ; lastly, if the excita- 

 tion and consequently the motor-reaction are sufficiently 

 energetic to be propagated from below upwards to the bulb 

 and protuberance, the reaction becomes general, is propagated 

 in every direction, both downwards and upwards ; in such a 

 manner that all the muscles of the body take part in it, the 

 bulb acting as a general focus whence radiate all the reflex 

 movements (law of generalization). 



The reflex movements, obeying the five above-named laws, 

 present, moreover, the remarkable fact that they are pro- 

 duced with a regularity, a co-ordination, which seems to indi- 

 cate that these reflex actions are adapted to a certain purpose 

 or aim ; it appears as if there were in the histological disposi- 

 tions of the spinal cord & pre-established mechanism, the mani- 

 festations of which so strongly impressed the first vivisectors, 

 that they (Robert Whytt, Prochaska, Legallois, Pfliiger) did 

 not hesitate to endow the spinal cord with certain psychical 

 properties, so vague and ill-defined, that they were designated 

 under the name of sensorium commune, volition, perception, 

 soul (the latter must not be confounded with the ecclesiastical 

 name " soul" ), etc. 



Thus a frog whose brain had been removed (to eliminate 

 every influence foreign to the spinal cord), reacted when the 

 foot was pinched, as if to defend himself; if the skin of one 

 of his extremities was cauterized by a drop of acid he would 

 wipe it off with his foot, if perchance the acid had been placed 

 upon the bend of the thigh or on the pelvic integument; more- 

 over, if the leg which was bent thus towards the thigh were 

 amputated, the animal, reduced to his medullary centre, was 

 seen, after useless and droll efforts to reach the injured part 

 (law of unilaterality), if the irritation persisted and espe- 

 cially if it increased, to use the limb of the opposite side (law 

 of symmetry) and rub or wipe the part irritated. Should 

 the irritation continue he would execute movements with 

 all his other limbs, a forward jump, in fact a flight. Reflex 



