41 6 MESSRS. F. GOTCH AND V. HORSLEY 



fibres, and thus of indicating which groups of fibres in the cord form the chief 

 channels of conveyance ; and the value of this method will be manifest when the 

 character of those previously used and the conflicting nature of their results, have 

 been placed before the reader. 



SECTION 3. OUR PRESENT KNOWLEDGE AS TO THE CONDUCTION IN THE CORD OF 



AFFERENT IMPULSES. 



We have already referred in Chapter II. to the investigations made by previous 

 experimenters in order to determine the paths of conduction in the spinal cord. It 

 will, however, be advantageous to select the most typical of these experiments and 

 discuss their results, in order that the scope of these methods, together with those 

 excellencies and deficiences which each possesses, may be clearly in the mind of the 

 reader, before the uses of that which we advocate and its results are entered upon. 



The various methods may be grouped as anatomical and physiological. 



I. Anatomical. 



The posterior root fibres have been traced into the spinal cord, and a considerable 

 number* (according to KOLLIKER the majority) of these have been seen to divide and 

 send branches up and down the cord. The further course of these fibres has up to 

 the present been traced only by the method of degeneration. 



(a.) It has been ascertained that when, in consequence of section of a lumbar 

 posterior root, the fibres upon its central side degenerate, the degeneration is con- 

 tinued in certain regions of the posterior column of the same side, such degeneration 

 up to the present only being seen in parts above the entering root. In other words, 

 the degenerated fibres present in the posterior root are represented in the cord above 

 the root by certain fibres in the posterior column of the same side. These fibres are 

 believed to be the direct continuation of some of the fibres in the root ; they are situated 

 in the postero-external column at first, but gradually shift towards the middle line as 

 they ascend, and ultimately occupy a definite portion of the postero-median column. 

 In addition to these fibres which appear to have a continuous course up the posterior 

 columns of the cord, there are others which show degeneration only in the immediate 

 neighbourhood of the entry of the root ; these are situated in the posterior root zone 

 and in the marginal zone, as well as .in the postero-external column. They are 

 characterised by only occurring in that portion of the cord which lies above the 

 root, and by being all on the same side of the cord as the lesion. Hence these 

 fibres, whilst in direct continuity with fibres in the root, either end (KOLLIKER) 



* GOLOI: ' Anat. Anzeiger,' vol. 5, pp. 1.3, 14. RAMON-Y.CAJAL : 'Trabajos del Laboratorio Anatomico 

 de la Faculdad de Medicina,' Barcelona, Abril, 1890. KOLLIKER : " Ueber den feineren Ban des Riicken- 

 marks," ' Sitzungsberichte d. Wiirzburger Phys.-Mcd. Gesellschaft,' 8. Marz, 1890. 



