PROPERTIES OF THE POSTERIOR ROOTS. 79 



Properties of the Posterior Roots of the Spinal Nerves. 

 It is unnecessary to follow out, from the date of the first 

 experiments by Magendie to the present day, the observa- 

 tions that have been made from time to time upon the prop- 

 erties of the roots of the spinal nerves. For many years, the 

 difficulties in operating upon animals high in the scale ren- 

 dered confirmatory experiments somewhat unsatisfactory. 

 The great German physiologist, J. Miiller, showed, in experi- 

 ments made upon frogs, in 1831, 1 that irritation of the pos- 

 terior roots produced no convulsive movements ; but he de- 

 spaired of operating satisfactorily upon warm-blooded animals. 

 Magendie, in his later experiments, 2 and Longet, in experi- 

 ments performed on dogs, published in 18ttl, s showed verv 

 satisfactorily that the posterior roots were exclusively sen- 

 sory, and this fact has been abundantly confirmed by more 

 recent observations upon the higher classes of animals. ITe 

 have ourselves frequently exposed and irritated the roots of 

 the nerves in dogs in public demonstrations, in experiments 

 upon the recurrent sensibility of the anterior roots, 4 and in 

 another series of observations upon the properties of the 

 spinal cord, which will be referred to hereafter. 



The remarkable anatomical peculiarity of the posterior 

 roots, which they have in common with all of the exclusively 

 sensitive nerves, is the presence of a ganglion. While we 

 have no distinct idea of the function of these ganglia in con- 

 nection with the transmission of impressions from the pe- 

 riphery to the centres, it has been shown to have a remark- 



1 MULLER, Nouvelles experiences sur Teffet que produit rirritation mechaniqut 

 et galvanique sur les ratines des nerfs spinaux. Annales des sciences natureUes, 

 Paris, 1831, tome xxiii., p. 100, et seq. 



2 MAGEXDIE, Lecons sur les fonctions et les maladies du systeme nerveux, Paris, 

 1841, tome ii., p. 52, et seq., quatrieme lecon, 3 mai, 1839. 



3 LOXGET, Recherches pathologiques et experimentales sur les prcprittes et let 

 fonctions des faisceauz de la moelle epinere et des racines des nerfs rachidiens. 



Archives generales de medecine, Paris, 1841, tome Ivi., p. 168, et seq. 



4 FLINT, JR., Experiments on the Recurrent Sensibility of the Anterior Roots of 

 the Spinal Nerves. New Orleans Medical Times, 1861, p. 21, et sen. 



106 



