MEDIATE SPINAL SYSTEMS. 805 



part of the efferent root system through a " mediate " cell system. Such 

 mediation may be vid one link-cell, or vid a chain of link-cells. The 

 spinal mediate cell systems may be classed as (1) intrinsic or purely 

 spinal, and (2) extrinsic or spino-encephalic and encephalo-spinal. 



Mediate cells of the spinal cord. 1. Intrinsic mediate systems. 



These probably form a large proportion of the fibres of the cord, especially of the 

 zone of white matter nearest to the grey. They contribute probably especially 

 to the minute nerve fibres filling the area between the ventral horn and the 

 base of the dorsal horn (lateral limiting layer). 1 It seems that the fibres 

 of the ventral part of the layer arise from cells of the ventral horn (Bruce). 2 

 As a rule, the longer the course of a nerve fibre in the cord, the nearer its place, 

 except at its immediate beginning or ending, to the periphery of the cord. 3 

 (In the periphery of course is included the dorsal median septum.) Of the 

 short fibres some pass tailward from their cells of origin, some pass headward. 

 Certain that ascend far lie near the lip of the ventral median fissure. 



A number of descending intrinsic spinal fibres are commingled with the 

 pyramidal fibres in the pyramidal area of the lateral column. After complete 

 degeneration of the pyramidal system, many sound fibres are left in the dog in 

 that area, 4 and in that area many fibres in the dog are myelinated before the 

 fibres of the pyramidal tract. 5 Miinzer, 6 after semisection of the cord of a 

 new-born rabbit at the nineteenth vertebra, performed total transection two 

 vertebrae lower when the animal was grown, and found about as many fibres 

 degenerate below the lesion on the semisected as on the intact side ; the fibres 

 omitting decussation must have been of intraspinal origin. I (with E. E. Laslett) 

 have by semisection subsequent to total transection similarly found evidence, in 

 the dog, of abundant spinal fibres descending in all regions of the ventro-lateral 

 columns and extending through many segments. Miinzer also in the new-born 

 rabbit excised one hemisphere, and after spinal semisection in the grown 

 animal found many degenerate fibres in the lateral column behind the lesion. 

 He did not find injury of the anterior corpus quadrigeminum, nor of the 

 cerebellum, produce spinal degeneration, and therefore many of the fibres 

 degenerating are probably intrinsic spinal. 7 



Some intrinsic spinal nerve fibres, fasc. dorsalis proprius (Barker), probably 

 both ascending and descending, lie among the root fibres of the dorsal column. 

 (Flechsig's "oval centre" respected in tabes dorsalisj Schultze's "comma 8 



1 Sherrington, Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 255 ; A. S. F. 

 Griinbaum, ibid., 1894, vol. xvi. p. 368. 



2 Rev. neurol., Paris, tome iv. p. 698 ; Scot. Med. and Surg. Journ., Edinburgh, 

 vol. i. p. 1. 



3 Miescher, Arb. a. d. physiol. Anst. zu Leipzig, 1870, S. 183 ; Sherrington, Journ. 

 PhysioL, Cambridge and London, 1893, vol. xiv. p. 298; E. Flatau, Neurol. CentralbL. 

 Leipzig, 1897, Bd. xvi. S. 11. 



4 Sherrington, Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 177 ; 1893, 

 vol. xiv. p. 255 ; Lowenthal, "Inausc. Diss." Geneve, 1885 ; Singer and Miinzer, Denkschr. 

 d. k. Akad. d. Wissensch., Wien, 1890, Bd. Ivii. S. 585. 



5 Sherrington, Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 177. 



6 Prag. med. WchnscJir., November 1895. 7 Miinzer, loc. tit.; also Bd. xx. No. 4. 

 8 Schultze's "comma tract" was first noted and figured by Charlton Bastian, Med.-Chir. 



Trans., London, 1867. Kahler and Pick, Arch. f. Psychiat., Berlin, 1880, also drew atten- 

 tion to it before Schultze, ibid., 1883. It is difficult to sunder it from the descending limbs 

 of the dorsal root fibres. On the question of endogenous dorsal column fibres, see Daxem- 

 berger, Ztschr. f. Nervenheilk. , 1897, S. 136 ; Gombault et Philippe, Arch, de med. expfr. et 

 d'anat. path., Paris, 1894, tome vi. ; S. Blum, " Inaug. Diss., Strassburg, 1895 ; Tooth, 

 "Spinal Degenerations," London, 1889 ; Barbacci, Sperimentale, Firenze, 1891, tome iii.; 

 Hoche, Neurol. CentralbL, Leipzig, 1896, Bd. xv., and A rch. f. Psychiat., Berlin, 1896, 

 Bd. xxvii.; Alex. Bruce and Muir, Brain, London, 1896, vol. xix. p. 333; Miinzer and 

 Wiener, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1897, Bd. xxxv. S. 114 ; Dejerine and 

 Thoari, Compt. rend. Soc. de biol., Paris, 1898 ; Zappert, Neurol. CentralbL, Leipzig, 1898, 

 Bd. xvii. S. 105; Alex. Bruce, Brain, London, 1897, vol. xx.; also P. Marie, Eedlich, 

 Dejerine and Spiller, and Dufour, L. Mann, and others. 



