RECURRENT SENSIBILITY. 81 



animal just killed, no convulsive movements are produced 

 by stimulating the posterior roots ; but if the anterior roots 

 be irritated, movements of the most violent character occur, 

 confined to those muscles to which the filaments of the roots 

 are distributed. There has never been any doubt upon this 

 point since the experiments of Hagendie ; and it is now uni- 

 versally admitted by physiologists, that the motor properties 

 of the mixed nerves are derived exclusively from their ante- 

 rior roots of origin from the spinal cord. The question has 

 arisen, however, whether the anterior roots be not also en- 

 dowed with sensibility, notably less in degree than the poste- 

 rior roots, but still marked and invariable. The sensibility 

 observed in the anterior roots is abolished by section of the 

 posterior roots ; and this property, which is thought to be 

 derived from the posterior roots, has been called recurrent 

 sensibility. 



Recurrent Sensibility. We have seen, in reviewing the 

 history of the discovery of the distinct function of the roots 

 of the spinal nerves, that even in the earliest experiments by 

 Magendie, it appeared that the anterior roots possessed sen- 

 sibility in a certain degree, though it was insignificant as com- 

 pared with the sensibility of the posterior roots. In his later 

 experiments, Magendie formularized these facts, and an- 

 nounced that the anterior roots were sensitive as well as 

 motor, but less sensitive than the posterior roots, and that 

 this sensibility was abolished when the posterior roots were 

 divided. 1 Later still, he failed to demonstrate this sensibility 

 of the anterior roots ; but it was finally shown that this oc- 

 curred in animals exhausted from pain and loss of blood, and 

 that the anterior roots were really sensitive under normal 

 conditions. 3 Longet claims to have discovered, in 1839, what 



1 MAGENDIE, Lemons sur les fonctions et les maladies du sysleme nerveux, Paris, 

 1841, tome ii., pp. 63, 78, quatrieme legon, 3 mai, 1839, cincjuieme lepon, 8 mai, 

 1839.. 



2 MAGEXDIE, Note sur la sensibilite recurrente ; Extrait des comptes 

 Paris, juin, 1847, tome xxiv., p. 3. 



