FUNCTIONS OF THE SPINAL CORD. 133 



folloAv one another in regular succession, as those of Respiration, for an im- 

 pression to give rise to that organic change in the Spinal Cord which shall 

 terminate in a muscular motion.* It will be desirable, therefore, to consider 

 the evidence upon which the statement rests, that reflex actions are independ- 

 ent of sensation, though ordinarily accompanied by it. 



174. In the first place, then, it has long been well known that, in the Hu- 

 man Jbeing, the Spinal Cord does not by itself possess, in the remotest degree, 

 the power of communicating sensory impressions to the mind ; since, when 

 its lower portion has been severed from the brain by injury or disease, there 

 is complete anaesthesia of all the parts of the body which derive their nerves 

 exclusively from it. Hence^it might be inferred, that, throughout the Verte- 

 brated classes, the spinal cord is equally destitute of sensibility; and that any 

 movements produced by stimuli acting through it, are the results of a physical, 

 and not of a sensorial change. This inference, however, has been disputed ; 

 and, if unsupported by other evidence, it would not, perhaps, be entitled to 

 rank as an ascertained truth. The very performance, by decapitated animals 

 of inferior tribes, of actions which had not been witnessed in Man under similar 

 circumstances, has been held to indicate, that the spinal cord in them has an 

 endowment which his does not possess. The possibility of such an explana- 

 tion however unconformable to that analogy throughout organized nature, 

 which, the more it is studied, the more invariably is found to guide to truth 

 could not be disproved. Whatever experiments on decapitated animals were 

 appealed to, in support of the doctrine that the brain is the only seat of sensi- 

 bility, could be met by a simple denial that the spinal cord is everywhere as 

 destitute of that endowment as it appears to be in Man. The cases of pro- 

 found sleep and apoplexy might be cited, as examples of reflex action without 

 consciousness ; and these might be met by the assertion, that in such condi- 

 tions sensations are /<?//, though they are not remembered. It is difficult, how- 

 ever, to apply such an explanation to the case of anencephalous human infants 

 (in which all the ordinary reflex actions have been exhibited, with an entire 

 absence of brain), without supposing that the Medulla Oblongata is the seat of 

 a sensibility, which we know that the lower part of the Spinal Cord does not 

 possess ; and of this there is no evidence whatever. 



175. Experiments on the lower animals, then, and observation of the phe- 

 nomena manifested by apoplectic patients and anencephalous infants, might 

 lead to the conclusion, that the Spinal Cord does not possess sensibility, and 

 that its reflex actions are independent of sensation. At this conclusion, Pro- 

 chaska, Sir G. Blane, Flourens, and other physiologists, had arrived.; but it 

 was not until special attention was directed to the subject by Dr. M. Hall, that 

 facts were obtained, by which a positive statement of it could be supported. 

 For the question might have been continually asked If the spinal cord in Man 

 is precisely analogous in function to that of the lower Vertebrata, why are not 

 its reflex phenomena manifested, when a portion of it is severed from the rest 

 by disease or injury? The answer to this question is twofold. In the first 

 place, simple division of the cord with a sharp instrument leaves the separated 

 portion in a state of much more complete integrity, and therefore in a state 

 much more fit for the performance of its peculiar functions, than it ordinarily 

 is after disease or violent injury ; and as the former method of division is one, 

 with which the Physiologist is not likely to meet in Man as a result of acci- 

 dent, and which he cannot experimentally put in practice, the cases in which 

 reflex actions are manifested, are likely to be comparatively few. But, secondly, 



* See Outlines of Physiology, 3d edit., p. 211. By many of the German Physiologists, 

 also, it is maintained that Sensation is a necessary link in the chain of reflex actions; 

 but as they employ the term sensation in a sense which does not involve consciousness, it 

 is obvious that their dissent from Dr. Hall's views is chiefly verbal. 



