188 Prof. MuJIer and Dv. Marshall Half 



acting on the sensitive mucous membrane, and this per- 

 ception exciting the medulla oblongata to discharge in the 

 motor nerves. Dr. Marshall Hall regards the further act 

 of deglutition in the oesophagus as the effect of the stimulus 

 acting immediately on the muscular fibres of the oesophagus, 

 and the result of the irritability of the latter, which may ap- 

 pear very doubtful*. Even in beheaded young animals -we 

 may, however, as already shown, observe the reflected mo- 

 torial excitement still following mechanical stimulation of the 

 pharynx. Dr. Marshall Hall next shows the permanent in- 

 fluence of this function in the sphincters. The sphincter ani 

 remains closed in a tortoise after decapitation, so long as the 

 lower part of the spinal marrow is uninjured, but instantly 

 becomes flaccid and opens, when the spinal marrow is re- 

 moved. 



" Dr. Marshall Hall divided the spinal marrow in a live Co- 

 hiber natrix between the 2nd and 3rd vertebrae. The motions 

 ceased at once, and when the animal was not stimulated it re- 

 mained quiet. But if it were stimulated, it continued moving for 

 a long time ; for at every altering position new parts ot" its 

 surface came in contact with the ground : gradually it again 

 became quiet, but the slightest touch again renewed the mo- 

 tion. 



>" Dr. Marshall Hall shows very beautifully the relation of 

 the voluntary, respiratory, and reflected motions, when he en- 

 deavours to prove, that the reflected motions which take place 

 after loss of the brain are not dependent on true sensation^ 

 but only on the centripetal nervous actions which take place 

 in sensations. Sensation, will, motion, are the three links 

 of the chain, when a motion is induced by pain; but if the 

 middle link be destroyed, the connexion between the first 

 and second with the consciousness ceases. We believe also 

 that the reflected motions on stimuli of the skin, which take 

 place after the removal of the brain, do not contain any proof 

 that the stimulus excited true sensation in the spinal mar- 

 row ; it is rather the centripetal conduction of the nervous 

 principle which commonly takes place in sensations, but which 

 here is no longer sensation, because it is no longer con- 

 ducted to the brain, the organ of consciousness. During 

 healtli also numerous reflected motions result from stimuli of 

 the skin, which do not come as true sensations to the con- 



* There may certainly be considerable doubt respecting the action of the 

 cesophagus — a doubt which nothing but careful experiment can solve. But 

 1 think I have proof that the cardia closes and opens upon the principle of 

 the reflex function, as well as the pharynx, and that it is under the influence 

 of the internal excito-motoryf or pneumogastric nerve. — M. H. 



