RECURRENT SENSIBILITY. 83 



sibility, showing that the recurrent fibres, if they exist, must 

 turn back near the periphery. 1 



The question now arises with regard to the exact mech- 

 anism of recurrent sensibility. The explanation offered by 

 Magendie and Bernard is, that there are actually fibres re- 

 turning from the posterior to the anterior roots ; that these 

 fibres are, of course, sensitive, and that irritation of the an- 

 terior roots is propagated toward the periphery, and returns 

 to the centres through the posterior roots. This explanation 

 satisfies all of the experimental conditions, and is further 

 sustained by the microscopical examinations of Schiff, and 

 of Philipeaux and Yulpian. It will be remembered that the 

 ganglia of the posterior nerves, after division of these roots, 

 have the remarkable power of preserving the anatomical 

 integrity of the fibres to which they are attached. Now, 

 it has been shown by Schiff that, after division of the pos- 

 terior roots beyond the ganglia, the anterior roots contain 

 altered fibres, which he believes come from the posterior 

 roots, and give to these roots their sensibility. Philipeaux 

 and Yulpian, in experiments on the regeneration of nerves, 

 showed that the peripheral ends of the sublingual and facial 

 nerves remained sensitive after division, and that after ten 

 or fifteen days, in the midst of a great mass of degenerated 

 fibres, were a few that possessed their normal characters. 3 

 The bearing of these facts will be better understood by re- 

 ferring back to the experiments of Waller on the influence 

 of the ganglia over the nutrition of sensitive nerves. 3 



Dr. Brown-Sequard offers a different explanation of the 

 pain developed upon irritation of the anterior roots. He 

 believes this to be due entirely to cramp or convulsive con- 

 traction of the muscles. 4 This may be accepted, perhaps, as 



1 BERNARD, Systeme nerveux, Paris, 1858, tome i., p. 28. 



8 VULPIAX, Lemons sur la physiologic generate ef. comparee du systeme ncrveux, 

 Paris, 1866, p. 150. ' See page 80. 



4 BROWN-SKQUARD, Course of Lectures on the Physiology and Pathology of the 

 Central Nervous System, Philadelphia, 1860, p. 8. 



