REPORT ON THE PHYSIOLOGY OF THE NERVOUS SYSTEM. 77 



posterior roots, no motion was induced in any part of the mus- 

 cular frame ; but on grasping the anterior roots, each touch of 

 the forceps was followed by a corresponding contraction of the 

 muscles supplied by the irritated nerve. Magendie has de- 

 scribed* the following experiments, which he has since declared 

 were made without any knowledge of the prior ones of Sir C. 

 Bell. The subjects chosen for the operation were puppies 

 about six weeks old; for in these it was easy to cut with a sharp 

 scalpel through the vertebrae and to expose the medulla. In the 

 first, the posterior roots of the lumbar and sacral nerves were 

 divided, and the wound closed : violent pressure, and even prick- 

 ing with a shai'p instrument, awakened no sensation in the limb 

 supplied by the nerves which had been cut ; but its motive power 

 was uninjured. A second and a third trial gave the same re- 

 sults. Magendie then divided in another animal, though with 

 some difficulty, the anterior roots of the same nerves on one 

 side. The hind limb became flaccid and entirely motionless, 

 though it preserved its sensibility. Both the anterior and pos- 

 terior roots were cut in the same subject with destruction of 

 motion and sensation. In a second paperf Magendie has re- 

 lated the following additional facts. The introduction of nux 

 vomica into the animal economy is well known to give rise to 

 violent tetanic convulsions of the whole muscular system. This 

 property was made available as a test of the functions of the 

 separate orders of nervous I'oots. It was found that, while all 

 the other muscles of the body were agitated, when under the 

 influence of this poison, by violent spasmodic contractions, the 

 limb, supplied by nerves whose anterior roots had been pre- 

 viously divided, remained supple and motionless. But when 

 the posterior roots only had been cut, the tetanic spasms were 

 universal. It would seem, however, that the seats of the two 

 faculties of conducting motion and sensation are not strictly 

 insulated by exact anatomical lines, but that they rather pass 

 into each other with rapidly decreasing intensity. Thus irri- 

 tation of the anterior roots, when connected with the medvdla, 

 gives birth, along with motive phenomena, to some evidences 

 of sensibility ; and, vice versa, stimuli applied to the posterior 

 roots, also undivided, occasion slight muscular contractions. 

 In this last case it is, indeed, probable that the irritation tra- 

 velled from the posterior roots upwards to the brain in the ac- 

 customed channel, and gave rise to a perception of pain, which 

 prompted the muscular effort. Indeed, after division of the 

 posterior nervous roots, ordinary stimulants, applied to the 



• Journal de Physiologie, torn. ii. p. 276. August 1822. f Ibhl torn. ii. p. 366. 



