512 THE SPINAL CORD. 



and lateral columns. Another set of fibres slant principally upwards, but some 

 downwards, in the posterior columns, and, interlacing with each other, most probably 

 enter the grey matter at different heights. Some are lost to view in the posterior 

 white columns, and it is uncertain whether or not they immediately ascend through 

 these columns to the brain. 



Much discussion has taken place as to the course of the fibres in the cord, and their 

 ultimate destination. It is easily understood that, by the examination of sections difficult 

 to prepare, limited in extent, liable to undergo changes in the preparation, and giving 

 views confined each to little more than a thin lamina, it is scarcely to be expected that 

 the full history of many tortuous fibres can be accurately ascertained. Thus it remains 

 still undecided whether any of the fibres of the nerve-roots pass up all the way to 

 the brain. Volkmann concluded that none of them reached the brain, arguing from 

 measurements of the size of the cord in different regions, that the cord could not 

 contain in its upper regions all those nerve-fibres which were traceable to it in the 

 lower. Kolliker pointed out the fallacy of this conclusion, in so far as Volkmann 

 had not made proper allowance for the diminished size of the fibres as they ascend in 

 the cord ; but although Volkmann's argument was thereby invalidated, it appears 

 impossible to prove by microscopic observations that fibres of nerve-roots traced into 

 the grey matter, and observed to emerge into the white matter, do not again re-enter 

 the grey and terminate there. (Lockhart Clarke, Phil. Trans., 1851,1853, 1859; 

 Stilling, Neue Unters. u. d. Bau des Ruckenmarks, 1856, 1857; Lenhossec, Neue 

 Unters. u. d. Bau d. cent. Nervensystems, Vienna, 1855 ; F. Goll, Beitrage z. feineren 

 Bau d. Ruckenmarks, Zurich, 1860. For a full account of the whole subject, see 

 Kolliker's Handbucb der Gewebelehre des Menschen, 4th ed., 1863). 



It is also undetermined in what relation the nerve-fibres and branched or multipolar 

 cells of the cord stand to each other. Most are inclined to believe that the radiating 

 prolongations of the cells are in actual con tinuity with the axial filaments of nerve-fibres, 

 whether proceeding from nerve-roots or from different parts of the cord itself; and 

 the direct observation of such continuity has been affirmed by some, as by Schroeder 

 Van der Kolk. But it is still considered by observers who have given most careful 

 attention to this investigation that, although such continuity may be regarded as of 

 the greatest probability, and, although it may be considered as proved in some other 

 parts of the nervous system, especially in the lower animals, the actual passage of 

 nerve-fibres into the processes of nerve-cells has not been proved as the result of 

 actual observation in the spinal cord of man or of mammals. 



Results of Experiments. Seeing the imperfect nature of the knowledge of the 

 minute structure of the spinal cord as obtained from microscopic observations, it 

 may be proper to give here a short account of the more important results of 

 physiological experiments as to the course of the transmission of sensory impressions 

 and motor influences through it, although it is at present difficult to reconcile them 

 with the results of anatomical research. For the most important information upon 

 this subject, derived from vivisection, science is indebted to the researches of Brown- 

 Se"quard and Schiff. 



When the superior or dorsal * half of the cord is divided in animals, sensation still 

 continues in the hind limbs. Sensation likewise continues after division of the 

 inferior half of the cord, and even after the superior and inferior parts of the cord 

 have been divided at different levels in such a manner that the hinder extremity of 

 the cord may be supposed to communicate with the brain by means of the central grey 

 matter only. But sensation is abolished by piercing the interior of the cord with an 

 instrument, and so moving it as to divide as much as possible the grey matter without 

 injuring the white matter. Moreover, section of the cord and irritation of the cut 

 surfaces produce no pain, provided that the plane of section be sufficiently removed 

 from the origins of nerves, as may be accomplished in the cervical region ; but in the 

 neighbourhood of nerve-roots there is great sensibility. From all these circumstances 

 it appears probable that the sensory fibres, viz., those of the posterior roots, pass 

 quickly into the grey substance, and that the grey substance conducts sensory 

 impressions upwards. Moreover, the circumstance that the posterior as well as the 

 anterior surfaces of transverse sections made near the nerve-roots are sensitive seems 



* The student is reminded that "superior" applied to animals corresponds to 

 " posterior" applied to the human subject. 



