DEGLUTITION AND DEFECATION. 149 



distinct set of muscles is provided to keep them in action. These muscles 

 have distinct ganglia as the centres of their operations ; and these ganglia are 

 only connected indirectly with those of the sensori-volitional system. The 

 same would appear to be the case in regard to the introduction of the food 

 into the digestive apparatus. It has been shown that the muscles concerned 

 in this operation have their own centres, the stomato-gastric and pharyngeal 

 ganglia, which are not very closely connected with the cephalic, or with the 

 respiratory, or with those of general locomotion. Now in the Vertebrata, the 

 distinct organs have been so far blended together, that the same muscles serve 

 the purposes of both ; but the different sets of movements of these muscles are 

 excited by different nerves ; and the effect of division of either nerve is to 

 throw the muscle out of connection with the function to which that nerve 

 previously rendered it subservient, as much as if the muscle were separated 

 from the nervous system altogether. There is an apparent exception to this 

 view of the matter, in the case of the Portio Dura ; this being the source of 

 those movements of the upper lip which, in many animals, are essential to 

 the prehension of food. These movements, however, are dependent upon 

 sensations conveyed through the Fifth pair,* being completely checked by 

 division of its infra-orbital trunk ; and it can scarcely be doubted, from their 

 general character, that they are of a strictly voluntary nature, and are not to 

 be regarded as part of the reflex associated movements in which that nerve is 

 concerned. 



197. Now although, in the adult Human being, the movements required to 

 convey the food to the pharynx are under the control of the Will, if not con- 

 stantly dependent upon it, there is good reason to believe that this is not the 

 case in regard to those remarkable associated movements which constitute the 

 act of suction in the Infant. The experiments provided for us by nature, in 

 the production of anencephalous monstrosities, fully prove that the nervous 

 connection of the lips and respiratory organs with the Spinal Cord, is alone 

 sufficient for its execution ; and Mr. Grainger has sufficiently established the 

 same, by experiment upon puppies whose brain had been removed. He adds 

 that, as one of the puppies lay on its side, sucking the finger which was pre- 

 sented to it, it pushed out its feet in the same manner as young pigs exert theirs 

 against the sow's dugs. On the whole, however, the act of suction belongs 

 more to the Respiratory ganglion (so to speak) than to the Stomato-gastric 

 system of nerves ; and hence we can understand why, even in the highest 

 animals, it should be purely instinctive ; the movements of Respiration being 

 so from the first, whilst those ordinarily concerned at a later period in the 

 ingestion of the -food are more directed by the will. The actions of the 

 mammary foetus of the kangaroo, described by Mr. Morgan, furnish a very 

 interesting exemplification of the same function of the Spinal Cord ; this crea- 

 ture, resembling an earth-worm in appearance, arid only about fourteen lines 

 in length, with a brain corresponding in degree of development to that of a 

 human fostus of the ninth week, executes regular, but slow, movements of 

 respiration, adheres firmly to the point of the nipple, and moves its limbs when 

 disturbed. The milk is forced into the oesophagus by a compressor muscle, 

 with which the mamma of the parent is provided. "Can it be imagined," 

 very justly asks Mr. Grainger, " that in this case there are sensation and 

 volition, in what can be proved anatomically to be a foetus ?" 



198. We now return to the question of the influence of the Spinal Cord 



* Hence originated one of Sir C. Bell's early errors. He found that an ass, in which 

 the infra-orbital branch of the fifth was divided, would not pick up oats with its lip, 

 although they were in contact with it; hence he concluded that its power of motion was 

 destroyed, when it was in reality only the sensation necessary to excite the will to 

 cause the motion that was deficient. 



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