REFLEX ACTION OF THE SPINAL CORD. 811 



perikarya and synapses. Among the agents are both depressants, as 

 ether and chloroform, and stimulants, as strychnin. 



Before it was established by Engelken l and others that the intraspinal 

 fibres are, like the peripheral nerves, excitable by various artificial stimuli as 

 well as by natural, the spinal paths of conduction were spoken of as aesthesodic 

 and kiiiesodic. These names (Schiff 2 ) implied that the paths would transmit 

 but would not initiate nerve impulses. 3 



The constant refuge sought at one period for an explanation of the 

 difficulty connected with travel of impulses along the cord in spite of intervening 

 incisions, was a hypothetical long path up the continuum afforded by the grey 

 matter. The grey matter is now no longer thought to offer such a continuum, 

 and it is not at all probable that any conducting path continues long within it. 4 



Many of the fine fibrils contributing to the interlacement in the grey 

 matter are " collaterals " from stem fibres. These appear to myelinate late 

 and to degenerate early. The fine fibrils in the grey matter of the vesicular 

 column of Clarke are usually much reduced in number, and may almost all 

 disappear as a result of degeneration of the afferent spinal roots. 5 After 

 removal of the Rolandic area of the cortex in the monkey, 6 I noted degenera- 

 tion in some of the small fibrils of the grey matter of the ventral and lateral 

 cornua of the cord. Mingazzini 7 has studied the disposition of the decrease 

 of the grey-matter fibrils in the human cord in lateral sclerosis. He concludes 

 that the interlacement of all but the mesial part of the ventral horn is made 

 almost entirely of pyramidal collaterals. To the postero-lateral group of the 

 ventral horn pass, in addition to collaterals from the lateral tract, numbers 

 of afferent root collaterals. Schafer 8 proves that the collaterals from the 

 pyramidal tract pass toward Clarke's column and the base of the posterior 

 horn; he denies that they go directly to the anterior horn. v. Lenhossek 9 

 brings forward some evidence that even the " direct reflex collaterals " from 

 the afferent roots do not reach actually to the efferent root cells, but act on 

 them only through mediation of intervening cells or cell branches. 



EEFLEX CAPACITY OF FRAGMENTS OF THE SPINAL CORD. 



Why tt 10 was first to show that integrity of even a fraction of the 

 length of the spinal cord suffices to enable reflex reactions to occur in 

 response to skin stimuli, and therefore that reflex function does not 

 depend on the integrity of the cord as a whole. Legallois 11 extended 

 similar observations to the mammalian cord. Striking examples of 

 reflexes from a quite short isolated length of spinal cord are the sexual 

 clasp by the fore-limbs of the male frog after section in front and 



1 Arch. f. d. gcs. PhysioL, Bonn, 1870, Bd. iii. S. 403 ; Biedermann, Sitzungsb. d. k. 

 Akad. d. Wissensch., Wieu, 1883, Bd. Ixxxvii. S. 3. 



2 "Lehrbuch d. Muskel- u. Nerven-physiol.," Lahr, 1858. 



3 It must not be forgotten that we have still no proof of the excitability of the grey 

 matter of the cord in response to stimulation by artificial (electrical and mechanical) means. 



4 See to the contrary, Ciaglinski, note 4, on previous page. 



5 Cf. Leyden, " Klin. d. Ruckenmark," Bd. ii. ; Lissauer, Fortschr. d. Med., Berlin, 1884 ; 

 Arch. /. Psyc/iiat., Berlin, 1885, Bd. xvi. S. 431 ; Krauss, Neurol. CentralbL, Leipzig, 

 1885 ; Hadden and Sherrington, Brain, London, 1888, vol. xi. p. 325 ; Dejerine, Arch, de 

 physiol. norm, et path., Paris, 1888, p. 331 ; Oppenheim, Arch. f. Psychiat., Berlin, 1889, 

 Bd. xx. ; Tooth, "Spinal Degen.," 1889 ; Mott, Journ. PhysioL, Cambridge and London, 

 vol. xi. p. 12 ; Sherrington, ibid., vol. xiv. p. 255. 



6 Journ. PhysioL, Cambridge and London, 1890, vol. xi. 



7 JRiv. sper. difreniat., Reggio-Emilia, 1892, tomo xviii. See also Fiirstner, quoted by 

 v. Lenhossek, "Der feinere-Bau des Nervensystems," Aufi. 2, Leipzig, 1895. 



8 " Proc. PhysioL Soc.," March 1899, in Journ. PhysioL, vol. xxiv. 9 Op. ciL, 405. 



10 "On the vital and other involuntary motions of animals," Edinburgh, 1750. 



11 "(Euvres d. Car. Legallois, avec notes d. M. Pariset," Paris, 1830, tome i. p. 135. 



