446 SPECIAL HISTOLOGY. 



the nerve-corpuscles of the central organs, and their processes, 

 in general, is still a disputed point, I am prepared to admit that 

 the fact may be otherwise. These researches have opened the 

 way, and I have no doubt, as I have already said in my 

 Microscopical Anatomy, that in time we shall succeed in 

 demonstrating the origin of dark-bordered tubes in many other 

 situations in the central organs, in man, and other animals. 

 On the other hand, however, supported by repeated investigation 

 of the human brain, I must assert, that it is in the highest 

 degree probable that in many places it will be altogether 

 impossible to demonstrate the origin of fibres from nerve-cells, 

 because very many nerve-tubes, particularly those of the cortical 

 substance of the cerebellum and cerebrum, ultimately become so 

 pale and slender, as not to allow of their being distinguished 

 from the processes of nerve-cells. Whether the loops which 

 distinctly exist in the convolutions of the cerebrum, and which 

 I have also seen in the corpora striata, are terminations, or 

 whether free prolongations of nerve-tubes exist, we know not, 

 and the less so because it cannot even be asserted that cer- 

 tain fibres really do terminate. It may fairly be assumed 

 that the fibres of the corpus callosum and the commissural 

 fibres in general, commence in the one hemisphere in connection 

 with cells and terminate in the other, and that the fibres which 

 proceed from the surface of the convolutions to the optic 

 thalami and corpora striata terminate in the latter, but to 

 assert, that it is so, is impossible, notwithstanding the visible 

 loops, for it may be that these latter are not terminations at 

 all, and that the fibres in question are all in the one place and 

 the other in connection with nerve- cells. That nerve-fibres 

 should originate independently of any connection with cells 

 would be contrary to all analogy, but in such an obscure sub- 

 ject we must always be prepared for much that is new, and be 

 careful not wholly to reject any possibility, simply from a priori 

 considerations. Several authors have noticed divisions of the 

 nerve-tubes in the central organs, such as, among the older ones, 

 Ehrenberg, Volkmann, E. H. Weber, and more lately also, 

 Hessling (' Fror. N. Notiz./ Ap. 1849, Jenaische, Ann. I, 

 p. 283), E. Harless (ibid., p. 284), and Schaffner (< Zeits. f. rat. 

 Med./ IX) in the brain of various vertebrate animals, especially 

 at the junction of the white and grey substance. I am not 



