646 FUNCTIONS OF THE CEREBRO -SPIN AL NERVOUS SYSTEM. 



which touches the arms of a Polyp is entrapped by them and drawn into 

 the stomach. But this action is attended with sensation, in the ordinary 

 condition of the higher Animal, apparently in order that guidance may be 

 tli us afforded in the performance of those other movements of prehension, 

 mastication, etc., by which the food may be brought within reach of the ap- 

 paratus of deglutition; and the sensations which are linked with these are 

 among the influences which prompt to those higher mental operations, 

 whereby food is provided for the digestive apparatus to make use of. The 

 Zoophyte is dependent for its supplies of aliment upon what the currents in 

 the surrounding fluid, or other chances, may bring into its neighborhood ; 

 and if these should fail, it starves. The aneucephalous Infant, again, can 

 swallow and even suck ; but it can execute no other movements adapted to 

 obtain the supply of food continually necessary for its maintenance, because 

 it has not a mind which sensations could awake into activity. The sensation 

 connected with excito-motor actions has not only this important end, but it 

 frequently contributes to enjoyment, as in Suction and Emissio Serninis. 

 The sensation accompanying the actions of this class, 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 sensatio'n that 

 ensues occasions unwonted movements, which are more or less adapted to re- 

 move the impediment, in proportion as they are guided by judgment as well 

 as by consciousness. Again, sensation often gives warning against incon- 

 venience, as in the excretory functions ; and here it is very evident, that its 

 purpose 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 ac- 

 tion of the sphincters ( 99). 



510. We have now to inquire how far the independent action of the 

 Spinal Cord is concerned in the general muscular movements of Man, and 

 especially in the locomotive actions of his inferior extremities. On this 

 point, it is obvious that we must not be guided by the analogy of the lower 

 animals; since the locomotive and other movements of Man are for the 

 most part volitional and purposive, and he has to acquire by experience that 

 control over his muscular apparatus which is necessary to enable him to per- 

 form them ; whilst in Invertebrata generally, and in a large part of the lower 

 Vertebrata, it is evident that the movements of progression, etc., which are 

 characteristic of each species, come under the general category of automatic 

 actions, and are provided for in the original organization of its nervous 

 centres, being performed without any education, and under circumstances 

 which render the notion of a purpose on the Animal's own part quite unten- 

 able. In so far as these instinctive movements require the guidance and 

 direction of sensations, they must be referred to the "consensual " group ; 

 but clear evidence is afforded by the continuance of many of them after the 

 removal of the centres of sensation, that they are excito-motor in their 

 character, and that they require no higher centre than the ganglia which 

 correspond to the Spinal Cord of Man. 1 There can be little doubt that the 

 habitual movements of locomotion, and others which have become "second- 

 arily automatic," may be performed by Man (under particular circumstances) 

 through the agency of the Spinal Cord alone, under the guidance and direc- 

 tion of the Sensorial centres, or even without such guidance; the required 

 condition being, that the influence of the Cerebrum shall be entirely with- 

 drawn. Thus, numerous instances are on record, in which soldiers have 

 continued to march in a sound sleep ; and the Author has been assured by 



1 See Princ. of Comp. Phys., \\ 649-654. 



