CLARKE, ON NERVE-FIBRE. 73 



contents of the nerve-fibre were squeezed out, they assumed 

 the same diversity of form. Fig. 21 a is a large globule 

 of white substance variously wrinkled ; in two other globules 

 (b b) the surfaces have been thrown into a kind of network 

 of wrinkles or folds, like the surface of the fibre, fig. 18. In 

 the globule (c) the ridges have a spiral arrangement ; and at 

 d, a fold or ridge arising from the inner contour, has 

 exactly the appearance of a tubule or fine fibre ; but near the 

 centre of the globule, it subsides into the smooth convex 

 surface which surrounds it.* 



After I had observed all these appearances as the effects of 

 manipulation, I carefully dissected another fresh nerve, and 

 having selected some uninjured primitive -fibres, like the one 

 represented in fig. 6, I introduced under the thin covering- 

 glass a little acetic acid, and watched the result. The imme- 

 diate effects were a multitude of very small depressions or 

 pits, which showed like the fine marks of a mezzotinto 

 engraving (see fig. 22). These were succeeded by deeper and 

 larger depressions prolonged in different directions, so that 

 the intervening elevations might have easily been mistaken 

 for tubules. Sometimes these ridges were more or less 

 longitudinal, but short, and resembled the elevations in the 

 fissured bark of a tree (see fig. 22). Sometimes they ran 

 transversely and obliquely, and joined in a complete network ; 

 or turned about in loops, or in spirals like the spirals seen at 

 the cut ends of fibres hardened in chromic acid (see figs. 22 

 and 23). It was evident that all these appearances were due 

 to the same state of the white substance as that which has 

 been shoAvn to be produced by mere mechanical disturbance. 



* Stilling maintains that in i\\e fresh nerve-fibre, the inner, like the outer 

 contour, does not form a continuous or uninterrupted line, but splits in 

 various ways, and sends processes to the axis-cylinder ; and that under a low 

 power (his figures are magnified 1100 diameters) it seems to have a con- 

 tinuous boundary line only because the " elementary tubules or fibres" pro- 

 ceeding from it cannot be seen on account of their extreme transparency in 

 the fresh state. " Wenn man aber bei starkeren Vergiosserungen sorgfaltig 

 untersucht, so wird man finden, dass die innere Contour, eben so wie die 

 aussere, nicht stets eiue linienformige Begrauzung bildet, sondern vielfach 

 unterbroehen ist, sich theilt, Foitsatze gegeu den Axencylinder hin aus- 

 sendet, und nach kiirzerem Verlaufe in Continuitat abgebrochenanscheiuend 

 aufhort, und dass sie nur deshalb den Auscheiu eiuer Begranzungslinie giebt, 

 weil die nach innen wie nach aussen auslaufenden Fasern oder Rohrchen, 

 wegen ihrer Durchsichtigkeit im frischen Zustande, nicht erkannt werdeu 

 kounen." ('Neue Untersuch.,' 4te Lief., pp. 730-31.) These divisions of 

 the inner contour, as well as the. processes or fibres which he believes it 

 sends to the axis-cylinder, are nothing more than the indentations, cor- 

 rugations, and folds shown in figs. 17 and IS to result from mere mecha- 

 nical injury. 



