DISTRIBUTION OF NON-MEDULLATED NERVE-FIBRES. 125 



is not too much coloured, we are able to follow from this 

 nervous sheath finer fibrillae which no longer exhibit nuclei, 

 and these fibrillae can be traced in the wall of the vessel itself, 

 where one or other of them divides into two bi'anches. 



In some cases I was able to convince myself of the fact 

 that these very fine fibrillae join by their branches, as I have 

 already described in the secondpart. The numberof fine nerve- 

 fibres surrounding the vessels in some places, where a small 

 artery divides into two branches, which very soon after that are 

 not easily to be distinguished from capillary vessels, is most 

 striking. This is especially the case when we have to do 

 with arteries so small that only here and there can we dis- 

 tinguish a very limited number of" smooth muscular fibres, 

 while, on the other hand, in the larger arteries which 

 possess a distinct middle coat of smooth muscular fibres, 

 the number of the accompanying nerve-fibres can be by 

 no means compared with those mentioned above. As 

 regards the finer nerve-fibres of the capillary vessels I need 

 not trouble the reader Avith a long descrijition, as I have 

 dealt with this question already in the second part. On the 

 capillaries of the muscular tissue of the frog's tongue I 

 have seen these relations with such distinctness and so plainly 

 that I do not hesitate one moment to adhere to every point 

 I have maintained. I refer to the fig. 3 of this third part : — 

 (a) represents a capillary vessel, (b) the coarse nucleated 

 nerve-fibres which, as may be seen, have a parallel course 

 with the vessel, and bend round the latter in opposite direc- 

 tion. From these spring off" (c) finer nerve-fibres which are 

 scarcely provided with nuclei, and which form a plexus round 

 the vessel like a sheath. From this plexus spring off (d) 

 still finer fibrillse which belong partly to the wall of the 

 vessel itself.^ 



1 If we compare our Fig. 3 with the figures given by Dr. Beale in his last 

 paper on this subject ('Monthly MicroscopicalJournal,' Jan., 1S72, Plate IV, 

 fig. 3 and 4), the substance of which had already been published by the same 

 investigator, who really was the first to mention non-niedul!ated nerves on 

 the capillary vessels several years since ('Philosoph. Transact.,' 1SG3, pi. Ix, 

 fig. 44; ' Philosoph. Transact.,' 1865, pi. xxii, fig. 15 ; 'How to Work with 

 the Microscope,' 4th edit., 1S6S, pi. xxix, fig. 192), everybody, even if 

 not thoroughly acquainted with this subject, will, I think, agree with me 

 that the difference between the results which Beale has obtained and my own 

 is not a small one. This difference consists chiefly in the fact tiiat Beale's 

 "ultimate nerve-fibres" correspond to my coarser non-meduUated nerve 

 fibres, as regards which I perfectly agree with Beale that they accompany 

 the vessel in a nearly parallel course and bend round it once or twice. 

 These nerve-fibres have been seen also by Kessel and Tomsa, as I have 

 already mentioned in the second part. What Beale has not seen at any time 

 in his preparations, and therefore doubts, is the great number of finer nerve- 



VOL. XII. NEW SER. I 



