PHYSIOLOGY OF THE NERVOUS SYSTEM. 



721o 



posterior, and the anterior roots solely in the an- 

 terior columns. Nothing, however, is more cer- 

 tain than that both roots are implanted in the 

 antero-lateral columns, and it is extremely doubt- 

 ful that the posterior roots have any connection 

 at all with the posterior columns. Hence, as far 

 as anatomy enables us to judge, this distinction 

 of function between the two columns cannot be 

 admitted. On the contrary, anatomy indicates 

 that the antero-lateral columns are compound 

 in function. Their connection with the 

 corpora striata and optic thai ami, and with 

 the rnesocephale through the anterior pyramids 

 and fasciculi innominati, their reception of 

 both the anterior and posterior roots, and their 

 size in each region of the cord bearing a direct 

 proportion to that of these roots, denote that 

 these columns with the associated vesicular 

 matter are the seat of the principal nervous 

 actions, both mental and physical, with which 

 the cord is concerned. 



This view of the office of the antero-lateral 

 columns is confirmed by comparative anatomy, 

 which shows that the bulk of the organ or the 

 variety in the size of its various parts depends 

 mainly on these columns. 



Pathological observations are also in favour 

 of this doctrine. They distinctly denote that 

 lesion of the antero-lateral columns impairs the 

 sensitive as well as the motor power to an extent 

 proportionate to the amount of lesion. It is worthy 

 of note, however, that while a slight lesion of 

 the cord appears sufficient to impair or destroy 

 the motor power, it requires a considerable ex- 

 tent of injury or disease to impair in any very 

 marked degree the sensitive power. Some 

 lesions of these columns destroy the physical 

 nervous actions of the diseased or injured part 

 of the cord augmenting those of the portion 

 below the seat of lesion, doubtless by increasing 

 its polarity ; this is seen especially in cases of 

 injury to the cord by fractures or dislocations 

 of the spine. 



Direct experiments afford no aid in deter- 

 mining the functions of the columns of the 

 cord. Attempts to expose this organ either in 

 living or recently dead animals are surrounded 

 with difficulties, which embarrass the experi- 

 menter and weaken the force of his inferences, 

 if, indeed, they afford any premises from which 

 a conclusion may be drawn. The depth at 

 which the cord is situate in most vertebrate 

 animals, its extreme excitability, the intimate 

 connection of its columns with one another, so 

 that one can scarcely be irritated without the 

 others being affected, the proximity of the 

 roots of its nerves to each other, and the diffi- 

 culty, nay the impossibility, of stimulating any 

 portion of the cord itself without affecting 

 either the anterior or the posterior roots, are 

 great impediments to accurate experiments, and 

 sufficiently explain the discrepancies which are 

 apparent in the recorded results of experi- 

 ments undertaken by various observers. More- 

 over, the resultant phenomena, after experi- 

 ments of this kind, are extremely difficult of 

 interpretation, especially with reference to sen- 

 sation. " The gradations of sensibility," re- 

 marks Dr. Nasse, " are almost imperceptible ; 



the shades are so delicately and so intimately 

 blended, that every attempt to determine the 

 line of transition proves inadequate. There is 

 a great deal of truth in an expression of Calmeil, 

 that it is much easier to appreciate a hemi-pa- 

 ralysis of motion than a hemi-paralysis of sen- 

 sation, if the anterior fasciculi of the cord 

 possess sensibility but only in a slight degree, 

 the mere opening of the spinal canal and laying 

 bare the cord must cause such a degree of pain 

 as would weaken or destroy the manifestations 

 of sensibility in the anterior fasciculi. This 

 has not been sufficiently attended to by expe- 

 rimenters. Again, the practice of first irritating 

 the posterior fasciculi, and afterwards the ante- 

 rior, must have had considerable effect in pro- 

 ducing the same alteration. It is plain, that in 

 this way the relation which the anterior fasci- 

 culi bear to sensation must be greatly obscured ; 

 yet, with the exception of some few experiments, 

 this has been the order of proceeding generally 

 adopted."* 



All the experimenters agree in attributing to 

 the antero-lateral columns more or less power 

 of motion, but we gain no satisfactory infor- 

 mation from this source respecting their sensi- 

 tive power, and probably for the reasons so 

 well expressed by Nasse in the passage above 

 quoted. But, indeed, we do not need the 

 appeal to experiment in reference to this ques- 

 tion, although, if a distinct and unequivocal 

 response could be elicited by means of it, the 

 additional evidence would be of great value. 



There is great difficulty in determining pre- 

 cisely the functions of the posterior columns of 

 the cord. 



Both anatomy and comparative anatomy are 

 opposed to the view which assigns them sensi- 

 tive power. In the first place, as already 

 stated, there is no evidence to show that the 

 posterior roots of the spinal nerves are con- 

 nected with them ; even Sir C. Bell, who once 

 held that these columns were sensitive because 

 the sensitive roots were connected with them, 

 gave up that view, having satisfied himself 

 that no such connection existed.f Secondly, if 

 they were sensitive, it is not unreasonable to 

 expect that they would exhibit an obvious en- 

 largement at the situations which correspond to 

 the origins of the largest sensitive nerves ; so 

 little, however, is this the case, that the pos- 

 terior columns exhibit little or no variation of 

 size throughout their entire course. Thirdly, 

 the researches of the morbid anatomist afford 

 evidence unfavourable to the assignment of the 

 sensitive function to these columns. Cases are 

 on record which show that disease of the pos- 

 terior columns does not necessarily destroy 

 sensibility; that perfect and even acute sensi- 

 bility is compatible with total destruction of 

 the posterior columns in some particular region, 

 the posterior roots remaining intact : and others 



* Nasse, Untersuchungen zur Physiologic und 

 Pathologic, Bonn, 1835-36. The passage is quoted 

 from on abstract of the work published in the Brit, 

 and For. Med. Review, vol. iv. 



f See his paper on the relations between the 

 nerves of motion and of sensation and the brain. 

 The Nervous System, p. 234. 8vo ed., 1844. 



