REGENERATION OF THE SPINAL CORD. 879 



that the spinal cord is reproduced in the lizard in the regeneration of 

 the tail. His description has been many times confirmed, and its fact 

 thoroughly established, 1 The regeneration takes place even when the spinal 

 cord has been transected above the tail, in the thoracic region. 2 But although 

 the new formation of both ependyma cells and nerve cells in the caudal cord is 

 clear and abundant, there is much less restitution of both these elements in 

 the cicatrix in the thoracic region. 3 Regeneration of the cord in the tail- 

 region of Lacerta viridis is less complete 4 than in that of Triton, and some 

 are doubtful whether the nerve cells reappear in the former, 5 though several 

 observers regard this as unquestionable. 6 In the tadpole the regeneration 

 only includes the ependyma cells. 7 In the adult frog, in spite of the observa- 

 tions of Masius and Van Lair, Sgobbo finds no karyomitosis or other signs of 

 nervous regeneration at the transection of the cord. Similarly, the results of 

 Brown-Sequard in the pigeon are contradicted by the careful observations by 

 Piccolo and Santa Silena, 8 and by Sgobbo. 9 After semisections and total 

 transections, these latter observers find in the pigeon no neoformation of nervous 

 elements, but degeneration of nerve fibres extending for various distances, 

 although the ependyma cells of the central canal remain almost unaltered, 

 quite close up to the seat of trauma. It seems an established fact, that in the 

 higher vertebrata, no karyomitosis goes on in the spinal nerve cells after that 

 early stage of development at which the dorsal white columns are sufficiently 

 formed to cause a distinct dorsal median fissure to the cord. 10 But as to spinal 

 regeneration, numerous observations upon dogs have led to somewhat discordant 

 conclusions. Regeneration of cells has been described ; n also the extension of 

 nerve fibres across the scar without any regeneration of nerve cells ; 12 whilst 

 by others neither regeneration of nerve cells nor extension of nerve fibres into 

 the scar could be found. 13 Karyomitosis has been found in the ependyma 

 cells of the central canal at the exit of lesion, but none in the nerve cells 

 proper. The neuroglia cells of adult animals normally show some karyomi- 

 tosis. 14 The origin of the new nerve fibres that in some cases traverse the 

 scar has not been ascertained. 



1 Muller, "Ueber Regeneration, u.s.w.," Wiirzburg, 1864 ; Collucoi, "Intorno all ripro- 

 duzione degli arti e della coda nei tritoni," Mem. Accad. d. sc. d. 1st. di Bologna, (4) tomo iv. p. 

 301 ; Barfurth, Anat. Anz., Jena, 1888, S. 312 ; Caporoso, "Sulla rigenerazione d. midollo 

 spinal e, " 1888; Magini. "Sulla rigenerazione d. midollo spinale caudale nel triton," 

 Bull. d. r. Accad. med. di Roma, 1890, tomo xvi. p. 88 ; Sgobbo, " Sulla rigenerazione del 

 midollo, etc.," Psichiatria, Napoli, 1890, p. 295. Of. S. Flexner, Journ. Morph., Boston, 

 vol. xiv. p. 337. 



2 Sgobbo, op. cit. s Ibid. 4 Magini, op. cit. 5 Magini and Sgobbo. 



6 Colori, Mem. d. r. Accad. d. sc. d. 1st. di Bologna, 1858, tome ix. p. 345 ; Muller, 

 op. cit. 



7 Barfurth, Sgobbo. 



8 "Sulla midolla spinale," Gior. de sc. nat. ed econ., Palermo, 1876, tome xi. 



9 Loc. cit. 



10 Ludwig Merk, DenJcschr. d. k. Akad. d. VFissensch^Wien, 1887 ; Tirelli, Ann. difreniat., 

 Turin, 1897, tomo v. p. 9 ; Monti and Fieschi, Arch. ital. de biol., Turin, tomo xxiv. p. 401. 



11 Dentan, "Inaug. Diss.," Bern, 1875 ; Masius, Arch, de Uol., Gand, 1880, tome i. 

 p. 696; Baer, Dawson and Marshall (Howell's laborat.), Journ. Exper. Med., Baltimore, 

 1898, vol. iii. p. 1. 



12 Eichhorst and Naunyn, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1874, Bd. ii. 

 S. 225 ; Eichhorst, Ztschr. f. Uin. Med., Berlin, 1879, Bd. i. S. 284. 



13 Westphal and Schiefferdecker, Virchow's Archiv, 1876, Bd. Ixvii. S. 542 ; Reckling- 

 hausen, loc. cit.; Sgobbo, loc. cit.; Kerestzzeghy and Hanss, Beitr. z. path. Anat. u. z. Allg. 

 Path., Jena, 1892, Bd. ii. S. 33; Fiirstner and Knoblauch, Arch. f. Psychiat., Berlin, 1893, 

 Bd. xxiii. S. 132 ; Friedmann, ibid., 1888, Bd. xix. S. 244. 



14 Nissl, Versl. d. sudwest deutsch. psychiat. Vereins, Karlsruhe, 1893. See Neurol. 

 Centralbl., Leipzig, 1894, Bd. xiii. S. 98. 



