670 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



[The experiments of Dr. Brown-Sequard, witnessed by the editor, are also 

 confirmatory of the results obtained by Van Deen, Stilling, Longet, and Clarke. 

 Section of the posterior column on either side diminished the sensibility of the 

 opposite side, at the same time that the operation caused great pain. Section 

 of the whole of the white matter of the cord, however, did not destroy sensi- 

 bility entirely, so long as the central gray matter was uninjured, thus showing 

 that it, as well as the white matter, was a medium for the conduction of sen- 

 sory impressions. An interesting fact has been witnessed in connection with 

 these experiments, viz. : a degeneration of the tract of white fibres on the op- 

 posite side from the wound, evidenced by the deposition of granular cells, the 

 beginning of a metamorphosis to be perfected after a lapse of time. This de- 

 generation has been shown by Dr. Turck, of Vienna, to be a consequence of 

 abrogation of function, the result either of disease or experiment j 1 and it mani- 

 fests itself both in the sensory and motor tracts, whenever the transmission 

 of motor impulses or sensory impressions has been arrested. The gray matter 

 is not subject to the formation within it of these abnormal cells, from which, 

 however, no conclusion can be absolutely drawn with regard to its power of con- 

 duction. ED.] 



705. It is difficult to reconcile with the experimental results already cited, 

 those of other Physiologists, which appear to show that the anterior and pos- 

 terior divisions of the Spinal Cord respectively minister to the motions of flexion 

 and extension. This notion, which originated with Bellingeri, 2 was afterwards 

 advocated by Valentin, 3 who inferred from his experiments that, if the posterior 

 column of the Spinal Cord of the Frog be irritated at the point at which the 

 nerves of either extremity are given off, that extremity is extended, and that if 

 the anterior column be irritated, the extremity is flexed; so that, since he ad- 

 mitted the anterior columns to be chiefly motor, and the posterior to be for the 

 most part sensory, it would appear that the motor fibres of the extensors pass 

 from the anterior into the posterior column, whilst those of the flexors are con- 

 tinued onwards in the anterior column. Confirmation of this inference was 

 obtained by Valentin from experiments on Mammalia ; and it is borne out ac- 

 cording to him, by pathological phenomena observed in Man. According to 

 this eminent physiologist, also, relaxation of the sphincters is analogous to the 

 extended state of the extremities ; and he has noticed a manifest relaxation of 

 the sphincter ani in the frog, when the superior part of the spinal cord was irri- 

 tated, so as to produce extension of the limbs. The experiments of Budge* 

 and Engelhardt, 3 however, led them to an opposite conclusion ; for it appeared 

 to them that, in Mammalia, the nerve-fibres which act upon the extensor mus- 

 cles are contained in the anterior columns, and those of the flexor muscles in 

 the posterior columns; whilst, as regards the Frog, the nerve-fibres connected 

 with the extensor muscles appeared to be situated posteriorly to those of the 

 flexors. The experiments of Harless, 6 again, have led him to regard the upper 

 part of the spinal cord in the Frog, between the 2d and 4th vertebrae inclusive, 

 as specially concerned in the flexion both of the anterior and posterior extremi- 

 ties; and the lower part, from the 5th to the 8th vertebrae inclusive, as in like 

 manner concerned in their extension. All .these results can only at present be 

 accepted as indicating that some such special arrangement of the nerve-fibres in 

 the Spinal Cord, having reference to the combination of different muscular 

 actions in groups, may have a real existence ; there is far too little accordance, 



" Uber Secondare Erkrankung einzelner Ruckenmarksstriinge und ihren Fortsetzungen 

 zum Gebirne," Vienna, 1851. 



2 "De Medulla Spinali, nervisque ex ea prodeuntibus," &c., Turin, 1823. 



3 "De Functionibus Nervorum Cerebralium et Nervi Sympathici," Bernse, 1830. 



4 " Untersuchungen iiberdas Nervensystem," 1841. 



6 "Miiller's Archiv.," heft 3, 1841. ' 6 Muller's Arcliiv.," 1846. 



