THE NERVOUS SYSTEM. i'2 ( .) 



add: 1. that in further investigations of this kind, chromic 



acid, or chromate of potass, is to be preferred to alcohol, 

 particularly also when caustic soda is cautiously employed 

 for the tracing of the course of the nerve-fibres in the grey 

 substance thus rendered transparent; and, 2. that in con- 

 junction with lower magnifying powers, the most powerful 

 should be employed, and the relations of the elementary con- 

 stituents should also be otherwise accurately investigated. 



The question as to the origin of the nerves in the me- 

 dulla oblongata, presents itself as one of the most difficult 

 nature. Most anatomists have hitherto been content to trace 

 the roots of the nerves as far as one or the other column; but 

 this is not sufficient. All the nerves enter at least once, or 

 even several times, into grey substance, in which and no where 

 else are their origins to be sought for. Now, it must be con- 

 fessed, that through Stilling's great pains, the fruits of which 

 I can, as it may be said, fully confirm, — all the ten pairs of 

 nerves at present under consideration have been traced in 

 their roots as far as perfectly definite points of the grey sub- 

 stance; but now comes for the first time the further question: 

 do they commence in these situations, or do they proceed 

 beyond them ? As true origins in the brain have never yet 

 been seen with certainty by any one, there remains nothing 

 but physiological analogies and reasons. As regards the former, 

 we see in all the spinal nerves, that they first penetrate trans- 

 versely as far as the grey substance, and then, only passing 

 through this, join the white columns, and we may thence suppose 

 that the cerebral nerves, which, in general, so closely resemble 

 them, are in the same condition, and the more so, because 

 these also at first penetrate transversely into the interior of 

 the medulla, and the grey substance, with which they come in 

 contact, corresponds with that of the cord. To this may be 

 added also, that if we make the ten last cerebral nerves ter- 

 minate in the grey substance, into which they may so readily 

 be traced, the decussated influence of the parts above, upon 

 them, which appears to be established by pathological pheno- 

 mena, cannot be explained in the case of any one of them 

 except the trochlearis, which decussates before it reaches its 

 grey substance. Now, in the accessorius and hypoglossus it is 

 actually possible to see that the fibres come out from the grey 



