E-ROWX-SEQUAIiD OW THE CENTRAL NEBYOTJS SYSTEM. 2G9 



and that for the most part admitted in Germany, and, with many 

 minor modifications, adopted by Van Deen, Valentin, Stilling, and 

 others. 



The theory of Sir Charles Bell, as modified and completed by 

 Longet, has been, until quite recently, so generally accepted in this 

 country, and is so universally known that it is hardly necessary to 

 state it. In brief, upon this theory, the spinal marrow is regarded at 

 once as a nervous centre enjoying an activity of its own, and as a 

 conductor intended to place the muscles, the surface and various 

 organs in connexion with the encephalon ; this double function is con- 

 sidered as due to the two kinds of substance which enter into its com- 

 position. As a centre, it is a producer of reflex phenomena, which 

 property is due to the grey matter, a substance supposed to be 

 devoid of the power of conveying either sensitive impressions, or man- 

 dates of the will, to muscles ; the conducting faculty resides entirely 

 in the white substance of the columns of the cord ; the posterior 

 columns are regarded as being destined exclusively for the transmis- 

 sion of sensitive impressions to the encephalon, while, on the con- 

 trary, the anterior and lateral columns are the sole channels through 

 which the influence of the will is conveyed to muscles. In other 

 words, the posterior columns and their corresponding nerve roots are 

 regarded as centripetal conductors ; the anterior and lateral columns, 

 with the anterior nerve roots, as centrifugal conductors, while the grey 

 matter is the dynamical, or force generating, element of this nervous 

 centre. The human mind loves systems, and it found in this theory 

 something so simple and so seductive as to be almost irresistible. 

 Yet now it must be set aside, and recorded in the history of physi- 

 ology with many other brilliant, but deceptive, doctrines. 



Van Deen has propounded, and Valentin, Stilling, and others have, 

 with various modifications, adopted, a theory in one respect funda- 

 mentally differing from the foregoing ; they assign to the grey matter 

 the function of conducting impressions. According to Stilling, 

 whose beautiful researches in anatomy, physiology and pathology 

 have done so much for science, the posterior half of the grey sub- 

 stance of the spinal marrow is the channel for the transmission of 

 sensitive impressions to the encephalon. Moreover, according to his 

 theory, there is no determinate and invariable course for sensitive 

 impressions, which may pass equally well by either lateral portions of 

 grey matter already indicated. Indeed, • Stilling holds that a very 

 small portion of the grey matter is still sufficient to permit the trans- 

 mission of sensitive impressions coming from parts situated behind 

 the lesion. Although this theory cannot at the present time be 

 accepted as exact, yet it will be found that it contains important 

 elements of truth, in assigning to the grey matter conducting power. 



It is a remarkable instance of how much may be done by bold 

 assertion, even when altogether unsupported by facts, that it has 

 been so generally believed that the grey matter is devoid of the 



