oti the Beflex Function of the Spinal Marrow, 55 



the same ideas, with the same instances and observations 

 on narcotized animals, were propounded in the same year by 

 JDr. Marshall Hall, in the Philosophical Transactions of 1833. 

 Although these ideas were formed by us independently of each 

 other, yet the great correspondence in the observations and 

 explanations is not difficult to account for, if one considers, 

 that the physiology of the nerves has attained a condition, such 

 that in pursuing the subject the most remote observers may 

 at the same time be led to similar new observations and ex- 

 planations. I shall in the following pages first communicate 

 my own observations, as they were originally formed, and 

 shall then compare them with the results of the English phy- 

 sician and physiologist. 



"When perceptions, which are produced by external stimuli 

 on sensitive nerves, produce motions in other parts, this never 

 takes place by a reciprocal action of the sensitive and motor 

 filaments of the nerves, but by the sensorial excitement acting 

 on the brain and spinal marrow, and from these back to the 

 motor filaments. This extremely important principle in phy- 

 siology and pathology requires a strong proof, which may be 

 very clearly attained empirically, and then explains a number 

 of physiological and pathological phenomena. 



" I shall first prove that the motor and sensitive filaments of 

 a nerve, after the connexion of their two roots, do not enter into 

 any connexion with one another, but run separately to their 

 respective parts, and that therefore, even in cases where the 

 nervous sympathy is not in play, the sensitive and motor fila- 

 ments of a nerve have no reciprocal action whatever. 



" The proof of this position may be shown clearl}' in the fol- 

 lowing manner: If a compound nerve be stimulated (after 

 being divided,) at its central portion, severe pain is produced, 

 and the animal may express this pain by motions of flight, 

 crying, &c. ; but the muscular nerves connected with the sti- 

 mulated portion are not excited to action. No twitchings 

 take place in the muscles which receive nerves from the divi- 

 ded trunk. 



" It may also be proved in the following way : As the three 

 nerves destined for the posterior extremity of the frog form a 

 plexus, which again gives off two nerves, so, if one of the lat- 

 ter nerves be divided and isolated from all its connexions 

 with the muscles, and then the central portion be mechani- 

 cally stimulated, the injury produces a centripetal excitement 

 of the sensitive fibres of this nerve ; but the other nerves, 

 proceeding from the same plexus, do not, when the isolated 

 nerve is injured, excite any twitchings in their muscles. 

 That moreover, the general twitchings that ensue on any 



