304 NEKVOUS SYSTEM. 



observed in the healthy body are explained by the theory of 

 reflex action. 1 These observations of Marshall Hall were, in 

 the main, confirmed by Miiller, the year succeeding their 

 first publication ; 3 and, by some writers, the credit of the 

 discovery of the mechanism of reflex action is given to both 

 Miiller and Marshall Hall. 



From the point of view which the present condition of 

 science enables us to take with regard to the reflex action 

 of the cord, we have to determine the accuracy of the obser- 

 vations of Marshall Hall, and to follow out the advances 

 that have been made by more recent observers. It is impor- 

 tant, as the first step in our inquiry, to ascertain the exact 

 condition of decapitated animals as regards their capacity 

 for muscular movements ; and upon this point there is some 

 difference of opinion. Marshall Hall thought that an ani- 

 mal, a frog, for example, after decapitation, was incapable 

 of any voluntary movement, or of any movement which did 

 not have, for its exciting cause, an external impression. "We 

 take the example of frogs, because these are the animals 

 most commonly used by experimenters. 



All who have experimented upon frogs have seen them 

 jump about vigorously after decapitation ; and the question 

 whether these be spontaneous movements, so called, or an 

 excito-motor action, is more difficult to determine than 

 would at first sight appear. It would be unphilosophic to 

 assume that because the animal has been decapitated, the 

 movements are due to external impressions only, if we use 

 this as evidence against the possibility of spontaneous 

 movements under these conditions. The obvious necessity 

 of the argument is to remove all possibility of external im- 

 pressions, or of irritation of the cord itself. Upon this 



1 MARSHALL HALL, Reflex Function of the Medulla Oblongata and Medulla 

 Spinalis, London, 1833 ; and, Memoirs on the Nervous System, London, 1837. 

 Marshall Hall states that his first publication appeared in the Proceedings of 

 the Zoological Society, in 1812. 



2 MULLER, Elements of Physiology, translated by Baly, London, 1840, pp. 761, 

 J99.* The first edition of M tiller's work was published in Berlin, in 1833. 



