60 NERVOUS SYSTEM. 



Finally, the protuberance and the cerebral peduncles com- 

 prise in addition motor-centres for the movements of the globe 

 of the eye (eyeball, etc.). 



If a study of the reflex centres situated in front of or above 

 the before-named centres is begun, new phenomena compli- 

 cate the inquiry : these are phenomena of perception, or of 

 volition, so-called, which will be studied with the cerebral 

 centres, properly so called ; but even at the level of the pro- 

 tuberance we shall have to admit phenomena of perception, 

 and we shall see that this is one of the principal seats of the 

 reception of sensations, but not of their conservation under 

 the form of memory, and of their awakening under the form 

 of ideas. So the physiological separation between the 

 cephalic portion of the spinal cord and the cerebral organs, 

 strictly speaking, is not perfectly distinct, and we cannot in 

 fact designate the protuberance as the seat of transition, as 

 a point half-way between the spinal cord, explanation of 

 whose functions is relatively so easy, and the brain, which pre- 

 sents so much more mysterious phenomena. 



To sum up, the reflex act will be always the fundamental 

 fact in the functions of every nerve centre; it maybe under- 

 stood, then, why so much attention is paid to the reflex actions, 

 their classification, the discovery of influences that can ex- 

 aggerate or diminish them, and that this study should be 

 principally occupied with the spinal portion of the cerebro- 

 spinal axis where the reflex action by means of experimen 

 tation is easily isolated from all phenomena which could 

 complicate it. We can merely pass rapidly in review over the 

 results obtained by this study, which commenced only at the 

 close of the last century. 



The word reflex, or reflection, applied to certain nervous 

 phenomena, was first used by Astruc (1743), who sought to 

 explain the functions of the brain, and particularly the motor- 

 reactions which follow a sensory impression, by a sort of 

 reflection of the latter striking against the columns of the 

 brain and being reflected like a luminous ray from a polished 

 surface. The comparison was well made to illustrate the 

 method of study of the reflex phenomena, but applied to the 

 brain itself could lead to no result, for in the latter these phe- 

 nomena are too complicated. It was only by following the 

 researches of Robert Whytt, Prochaska, and Legallois, upon 

 the spinal cord, and upon that which is called the sensorium 

 commune, that Prochaska himself was able to distinctly indi- 

 cate both the principal seat (spinal cord) and the substance 



