546 APPENDIX. 



bundles of which interlace, yielding to one another one or more bundles, 

 and the chords which emerge from the plexuses deriving their component 

 filaments from different bundles: these bundles, and their component 

 threads, during their interlacing, will be seen to preserve their indi- 

 viduality. 



" When a chord going from th*e arachnoid, terminates on a cerebral 

 nerve, it divides in the same manner as an artery, some filaments ascend- 

 ing and others descending, along with the nerve tubules. In some in- 

 stances this extremity terminates in a sort of membranous expansion, 

 which encloses several nerve tubules." 



Mr. Rainey, in the next place, enters upon the consideration of the 

 nature of the above-described apparatus of ramifying chords and 

 plexuses, and arrives at the conclusion, derived from their relations and 

 intimate structure, that they are composed essentially of gelatinous or 

 sympathetic nerve filaments. 



" In the chords of the arachnoid (he writes) I could distinguish three 

 different kinds of filaments, all which exist in the branches of the sym- 

 pathetic. 



" One species, generally considered the most characteristic, is the 

 nuclear fibre described by Henle ; it is a flat, clear fibre, with oval, nearly 

 equidistant nuclei, and each having its long axis corresponding to that of 

 the fibre. I have found these fibres in the arachnoid, but they are very 

 rare. I have seen such going from the arachnoid to the coat of the in- 

 ternal carotid, the trunks being blended with the membrane, and the 

 branches connected with the artery. I also found, that as the fibres 

 branch off from these trunks, and intermix with others, they lost their 

 nuclei, became more pale and clear, and differed in no respect whatever 

 from the other fibres of the membrane. Besides, I have seen these 

 fibres in other parts of the membrane, and they exist chiefly on the ex- 

 terior of the larger chords. This species of fibre I have also found to be 

 very uncommon in the smaller branches of the nerves confessedly sym- 

 pathetic, especially in those most remote from the ganglia and larger 

 trunks. The next kind of fibre is one consisting of bundles, for the most 

 part rather smaller than nerve tubules, of very minute wavy filaments, in- 

 termixed with small particles of granular matter, having no definite form, 

 size, or position in respect to the filaments. Some of the chords of the 

 arachnoid are made up entirely of fibres of this description ; in others 

 they exist chiefly on their surface, being most abundant near their at- 

 tachment to the arachnoid, upon which they are continued. This kind 

 of fibre exists abundantly in all the branches of the nerves undoubt- 

 edly sympathetic ; and also, more or less, in those connected with the 

 ganglia. The third kind of fibre occurs in the form of roundish, though 

 sometimes flat chords, composed of extremely minute wavy filaments, 

 either collected or not into bundles, but apparently interwoven some- 

 what together, so that, generally, a filament of only an inconsiderable 

 length will admit of being detached mechanically from the rest, and, 



