FUNCTIONS OF THE SPINAL CORD. REFLEX ACTION. 291 



reach of the apparatus of deglutition. The Polype is dependent for its sup- 

 plies of aliment, upon what the currents in the surrounding fluid, or other 

 chances, bring into its neighbourhood; but anything which touches its ten- 

 tacula, is entrapped and conveyed into its stomach. The anencephalous 

 Infant, again, can swallow, and even suck; but it can execute no other move- 

 ments adapted to obtain the supply of food continually necessary for mainte- 

 nance, because it has not a mind which sensations could awake into activity. 



372. The sensation connected with reflex actions has not only this import- 

 ant end, but it frequently contributes to enjoyment, as in suction and ejaculatio 

 seminis. Now there is evidence that the latter of these processes, involving 

 though it does the combined action of a number of muscles, and dependent 

 as it seems upon sensation of a very peculiar kind, may take place without 

 consciousness on the part of the individual. Brachet mentions a case of this 

 kind in the Human subject, in which the patient's own testimony could be 

 adduced ; and he ascertained that emission could be produced in dogs, in 

 which the spinal cord had been divided in the back, and in which, therefore, 

 it can scarcely be doubted that the sensibility of the genital organs was de- 

 stroyed. Such cases, it might be thought, are sufficient to prove, that the 

 Reflex power, operating independently of sensation, is not confined to such 

 irregular convulsive movements as are seen in Man after disease or injury; 

 but is exercised in producing the regular combined actions which are neces- 

 sary for the maintenance of the organic functions. The sensation accompa- 

 nying these actions, moreover, frequently affords premonition of danger, or 

 gives excitement to supplementary actions destined to remove it, as in the 

 case of respiration; for where anything interferes with the due discharge of 

 the function, the uneasy sensation that ensues occasions unwonted move- 

 ments, which are more or less adapted to remove the impediment, in propor- 

 tion as they are guided by judgment as well as by consciousness. Again, 

 sensation often gives warning against inconvenience, as in the excretory func- 

 tions; and here it is very evident, that its object is not only (if it be at all) to 

 excite the associated muscles necessary for the excretion, but actually to make 

 the Will set up the antagonizing action of the sphincters, as will be hereafter 

 explained ( 391). There is one unequivocal case, in the ordinary condition 

 of the human body, of reflex action without sensation; this is the muscular 

 contraction, by which the food is propelled from the bottom of the pharynx 

 to the stomach. Unless the morsel be very bulky, so as to press on the sur- 

 rounding parts, or be very different in temperature from the surface it touches, 

 or have any peculiar irritating quality, we are not more conscious of its pre- 

 sence, whilst it is passing down the lower part of the oesophagus, than when 

 it is being propelled along the intestinal tube; and yet, as Dr. J. Reid's ex- 

 periments* have shown, this contraction is of a reflex character, not being 

 stimulated by direct contact, but requiring the completeness of the nervous 

 circle for its performance. 



373. We shall now separately consider the chief operations, in which the 

 Spinal Cord and its system of nerves are usually concerned, in the ordinary 

 course of the vital actions of the Human body. Upon taking a general sur- 

 vey of these, it will be found that their principal function is, to supply the 

 conditions requisite for the maintenance of the various Organic processes. 

 Thus, the aeration of the blood, which takes place whenever that fluid is 

 placed in relation with the atmosphere, can only be carried on, by the regular 

 exchange of the small quantity of the gas contained in the lungs ; if this 

 cease, the circulation is soon brought to a stand, and loss of vitality of the 

 whole system speedily results. Hence this is the most constantly necessary 



* Ediub. Med. and Surg. Journ., vol. xlix. 



