430 SPECIAL HISTOLOGY. 



substance, reached by them in the first instance, and after- 

 wards decussate; and the same thing is also at least probable 

 in the oculo-motorius ; so that I thiuk it may be, that 

 all the nerves now in question undergo decussation, and do 

 not terminate in the so termed nuclei of Stilling. Further 

 investigation will have to show whether this [decussation] 

 takes place in the floor of the fourth ventricle, as would appear 

 to be the case; whether all the fibres of these nerves take part 

 in it; and where the fibres proceed to after decussation. 

 With respect to the latter, it may be supposed from analogy 

 with the spinal nerves, that the true origin of the cerebral 

 nerves is probably not in the medulla oblongata, but in the 

 corpora striata aud optic thai ami. Of that portion of the portio 

 major n. trigemini, which is continued into the restiform body, 

 this may especially be remarked, that it certainly does not 

 originate in that part, but winds round it to somewhere above, 

 as is the case also with the n. accessorius. 



However, in stating, in accordance with what has been said, 

 that I do not consider it directly probable, that the sensitive 

 and motor cerebral nerves originate in the medulla oblongata 

 and pons, it is by no means intended to imply that these parts 

 may not, as central organs, exert some influence upon them 

 and the more deeply placed nerves. If the medulla oblongata 

 preside over the respiratory movements, if it and the pons be 

 the agents of multiplied reflex motions, this may be the case, 

 without its following that all the nerves called into action 

 should terminate in them, and simply for the reason that the 

 grey substance, so abundantly contained in them influences 

 the nerves which traverse it, exactly as must be supposed to 

 be the case in the spinal-cord.] 



§115. 



The cerebellum, with respect to the distribution of the 

 elementary tissues, exhibits tolerably simple conditions, grey 

 substance occurring only on the surface of the convolutions, 

 in the nucleus dentatus j and in the roof of the fourth ventricle; 

 all the remainder consists of white substance. The latter is 

 wholly constituted of parallel, probably unbranched, dark-bor- 

 dered nerve-fibres, possessing all the characters of central fibres 

 (softness, proneness to become varicose, easy isolation of the 



