THE NERVOUS SYSTEM. 117 



inclined to doubt these statements, especially the latter, but I can- 

 not avoid the remark, that in the human brain, I have, hitherto, 

 in vain sought for divisions of this kind, and have had many 

 hundreds of fibres from the grey substance before me, under 

 the most favorable circumstances, which presented no indica- 

 tions of the sort, whilst I have invariably found such divisions 

 iii the spinal cord (vid. supra). The many rayed nerve-cells 

 with branched processes are not as yet fully known in all their 

 relations. I have described their processes, (as will be 

 universally allowed, correctly,) as a sort of pale, non-medullated 

 nerve-tubes, and have isolated them occasionally to the extent 

 of i and i'", without being able to notice anything more with 

 regard to their termination, than the fact of their ultimately 

 assuming an extreme degree of fineness. R. Wagner states, 

 that those processes, which do not pass into dark-bordered nerve- 

 tubes, 'serve to connect the separate nerve-cells together, but 

 in so doing he manifestly says more than actual observation 

 warrants, as he has, hitherto, seen such a connection, only in the 

 electric lobes of the Ray. In the present state of neural 

 Anatomy there is nothing which should be more carefully avoided 

 than the general application of isolated observations, and I am 

 therefore of opinion that this question must as yet be regarded 

 as an open one. It may indeed be very consonant with 

 physiological considerations, to explain the reflex and alternating 

 actions of separate sections of nerves by such connections between 

 the cells, but it is precisely for that reason, that we should be 

 the more careful, and the more so because less obvious theories 

 explain the conditions just as well. I conclude, therefore, from 

 the observations hitherto made, only this much, that nerve- 

 cells may anastomose, leaving it to future inquiries to decide, 

 whether they do so universally and with all their processes, or 

 whether in certain situations the latter do not stretch out 

 without any attachment, exerting a mutual influence and 

 affecting the nerve-fibres simply by juxta-position, as appears 

 to be the case in the large nerve-cells of the cord and the roots 

 of the spinal nerves.] 



§ 118. 



Membranes and Vessels of the central Nervous System. — A. 

 Membranes. 1. Spinal cord. The dura mater s. meninx 



