TRANSACTIONS OF SECTION D. DEPT. ANATOMY AND PHYSIOLOGY. 711 



showed that the involuntary motion which such preparations execute ceases when 

 the whole of the spinal chord is destroyed — that if the back part of the chord is 

 destroyed, the motions of the hind limbs, if the fore part, those of the fore limbs 

 cease. It was in 1751 that Dr. Whytt published in Edinburgh his work on the in- 

 voluntary motions of animals. After this the next great step was made within 

 the recollection of living physiologists ; a period to which, as it coincided with 

 the event which we are now commemorating — the origin of the British Association 

 — I will now ask your special attention. 



Exactly forty-nine years ago Dr. Marshall Hall communicated to the Zoological 

 Society of London the first account of his experiments on the reflex function of 

 the spinal chord. The facts which he had observed, and the conclusions he drew 

 from them, were entirely new to him, and entirely new to the-physiologists to whom 

 his communication was addressed. Nor can there be any reason why the anticipa- 

 tion of his fundamental discovery by Dr. Whytt should be held to diminish his 

 merit as an original investigator. In the face of historical fact, it is impos- 

 sible to regai'd him as the discoverer of the ' i-e'flex function of the spinal chord,' 

 but we do not the less owe him gratitude for the application he made of the 

 knowledge he had gained by experiments on animals to the study of disease. For 

 no one who is acquainted with the development of the branch of practical medicine 

 which relates to the diseases of the central nervous system, will hesitate in 

 attributing the rapid progress which has been made in the diagnosis and treatment 

 of these diseases, to the impulse given by Dr. Marshall Hail to the study of nervous 

 pathology. 



In the mind of Dr. Marshall Hall the word reflex had a very restricted 

 meaning. The term ' excito-motory function,' which he also used, stood in his 

 mind for a group of phenomena of which it was the sole characteristic that a 

 sensory impression produced a motor response. During the thirty years which 

 have elapsed since his death the development of meaning of the word reflex has 

 been comparable to that of a plant from a seed. The original conception of 

 reflex action has undergone, not only expansion, but also modification, so that in its 

 wider sense it may be regarded as the empirical development of the philosophical 

 views of the animal mechanism promulgated by Descartes. Not that the work of 

 the past thirty years by which the physiology of the nervous system has been con- 

 stituted, can be attributed for a moment to the direct influence of Descartes. The 

 real epochmaker here was Johannes Miiller. There can be no doubt that Descartes' 

 physiological speculations were well known to him, and that bis large acquaintance 

 with the thought and work of his predecessors conduced, with his own powers of 

 observation, to make him the great man that he was ; but to imagine that his 

 ideas of the mechanism of the nervous system were inspired, or the investiga- 

 tions, by which, contemporaneously with Dr. Marshall Hall, he demonstrated the 

 fundamental facts of reflex action, were suggested by the animal automatism 

 of Descartes, seem to me wholly improbable. 



I propose, by way of conclusion, to attempt to illustrate the nature of reflex 

 action in the larger sense, or, as I should prefer to call it, the Automatic Action 

 of Centres, by a single example — that of the nervous mechanism by which the cir- 

 culation is regulated. 



The same year that J. R. Mayer published his memorable essay, it was dis- 

 covered by E. H. "Weber that, in the vagus nerve, which springs from the medulla 

 oblongata and proceeds therefrom to the heart, there exist channels of influence by 

 which the medulla acts on that wonderful muscular mechanism. Almost at the 

 same time with this, a series of discoveries' were made relating to the circulation, 



' The dates of the discoveries relating to this subject here referred to are as 

 follows : — Muscular Structure of Arteries, Henle, 1841 ; Function of Cardiac Vagus, 

 E. H. Weber, 1845 ; Constricting Nerves of Arteries, B. Sequard, 1852, Aug. Waller, 

 1853 ; Cardiac Centre, Bernard, 1858 ; Vascular Centre, SchifF, 1858 ; Dilating 

 Nerves, SchifE, 1854 ; Eckhard, 1864 ; Loven, 1866. Of the more recent researches 

 "by which the further elucidation of the mechanism by which the distribution of 

 blood is adapted to the requirements of each organ, the most important are those of 

 Ludwig and his pupils and of Heidenhain. 



