OE1GINAL AETICLES 5 



terior root in man which showed degenerated fibres extending 

 below into the lowest sacral region. 



It will be seen from the above that two chief sets of fibres 

 show under certain circumstances descending degeneration in the 

 posterior columns of the spinal cord ; one set lying in close 

 apposition to the inner margin of the posterior horns and in the 

 comma tract area ; the other set lying more mesially in the 

 posterior median columns. 



Whether these fibres are to be considered as being entirely of 

 endogenous origin, as is supposed by Daxenberger, Dufour, Mar- 

 gulies, Pierre Marie, Mayer, Philippe, Schaffer, Tooth, Worotynski, 

 Gombault, etc., or whether with Bruns, Flatau, Eedlich, Reimers, 

 Schiiltze, Singer, Zappert, etc., they are to be considered as ex- 

 clusively arising from the descending branches of the posterior 

 roots, therefore of exogenous origin ; or whether, as the writer 

 considers with Dejerine, Mliller, Eussell, Sottas, Wallenberg, etc., 

 they are both endogenous and exogenous, need not be gone into 

 here. 



The discrepancies in the descriptions by the various authors 

 as to the exact level at which the oval field of Flechsig or other 

 tracts appear or attain their maximum development are, as 

 Bruce has pointed out, no doubt due partly to the differences in 

 the nature and situation of the lesion, and partly to the different 

 methods of investigation employed. To this should, 1 think, be 

 added the fact that all these tracts contain short, intermediate 

 and long fibres ; that, in a word, they are really a series of tracts 

 superimposed ; and that therefore it is impossible in one section 

 either to divide all the fibres of a given tract or to produce 

 degeneration in the whole length of any fibre. 



STIMULATION OF THE POSTEEIOR COLUMNS AND POSTERIOR ROOTS. 



In a research carried out on monkeys and dogs about ten or 

 twelve years ago, the results of which were published in the 

 Philosophical Transactions of the Eoyal Society for 1895, the 

 writer (26) showed that whereas stimulation, say of the third 

 lumbar anterior root, produced rapid extension of the whole 

 hind limb of the same side in the above animals, stimulation of 

 the corresponding posterior root, or still more of the corre- 

 sponding part of the posterior columns, gave a strong, though 



