96 DR. MARTIN BARRY ON FIBRE. 



102 a, (3, y), having the same structure as those constantly referred to in the pre- 

 sent memoir. These filaments, forming the white substance of the nervous fibre, are 

 often seen to be curiously interlaced (fig. 102 y), as though each filament had a spi- 

 ral form. In other instances their direction is more longitudinal (fig. 112 a). 



29. Professor MULLER justly says, " The great size of the so-named primitive fibres 

 of the nerves, as compared \vJth the minute elementary parts of muscles, the cellular 

 and other tissues, excites a doubt as to whether the fibre contained in the nervous 

 cylinder is really its most minute element-f-." He states that "in fibres of the thick- 

 ness of the ordinary primitive fibres, which SCHWANN examined in the mesentery of 

 the Frog, he saw other much finer filaments which issued from the larger fibre;}:." 

 To the filaments seen by SCHWANN, I shall refer in a future page. MULLER adds, that 

 " TREVIRANUS observed in several nervous cylinders streaks running longitudinally, 

 and he even saw distinctly more minute elementary filaments in the so-called primi- 

 tive cylinders ." 



30. The filaments noticed by TREVIRANUS, I think may have been the flat filaments 

 in question. But these flat filaments, as we have seen, have themselves a compound 

 structure. 



31. It is very common to find the nerve-cylinder ("primitive fibre") drawn out to 

 a point from manipulation, like the fasciculus of muscle. See remarks on the alter- 

 ation of the spirals in the muscular fasciculus, and on the office performed by the in- 

 vesting membrane, in this change (par. 54). 



32. The filaments in fasciculi from the optic (fig. 107), olfactory (fig. 108), and audi- 

 tory nerves, have appeared less tense than those in the common spinal nerves ; and 

 there has been a less decided appearance of membrane at the surface in the former. 



33. In examining the substance of these soft nerves, as well as that of the brain 

 and spinal chord, I have employed for the most part such as had been preserved in 

 spirit : and, besides using extremely minute portions, I have very often found it need- 

 ful to avoid adding any covering whatever ; the weight of thin mica itself being suf- 

 ficient to rupture or to flatten it, and thus entirely prevent the structure from being 

 seen. I have already stated it to have been my general practice in these examina- 

 tions, to add corrosive sublimate dissolved in dilute spirit (par. 7). 



34. In the substance of the brain and spinal chord, I have usually met with a very 

 large number of discs (fig. 17 , |3), which from their colour, size, and general appear- 

 ance (corresponding in these respects with many of the corpuscles within the blood- 

 vessels of the pia mater), seemed to be young corpuscles of the blood. Along with 

 these were rings (y) and coils of filaments (S, t, t), into which the discs appeared to 

 pass. I have noticed similar rings in the auditory and optic nerves ; and coils, as 

 well as rings, in the retina (fig. 18), these coils being of the colour of the blood-cor- 

 puscle. Sometimes the coils (fig. 21) are very thick, and comparable to coils of rope. 



t Elements of Physiology, translated by Dr. BALY, Part III. p. 597. 

 J Ibid. pp. 597, 598. Ibid. p. 598. 



