862 STRUCTURE OF GREY MATTER. [BOOK in. 



the one hand, the fine medullated fibres spoken of above as being 

 recognized with difficulty, and, on the other hand, non-medullated 

 filaments ranging from fairly wide and conspicuous naked axis- 

 cylinders down to fibrils of extreme tenuity, the latter arising 

 apparently either from the division of axis-cylinders of nerve fibres 

 passing into or out of the grey matter or from the continued 

 branching of processes of nerve cells. By the modes of prepara- 

 tion now available it has been shewn that the fine medullated fibres 

 so far from being rare, are in certain parts of the grey matter so 

 abundant as even to preponderate over the non-medullated fibres 

 or fibrils. Lastly, besides the conspicuous nerve cells spoken of 

 above, which, though of various sizes, may all perhaps be spoken 

 of as large, a very large number of other cells of small size, some 

 of which at all events must be regarded as true nerve-cells, are 

 present in the grey matter. 



The neuroglia in which all these structures, nerve-cells, fine 

 medullated nerve-fibres, naked axis-cylinders and fine filaments, 

 are imbedded is identical in its general characters with that of 

 the white matter, but, as naturally follows from the nature of the 

 nervous elements which it supports, is differently arranged. In- 

 stead of forming a system of tubular channels it takes on the form 

 of a sponge work with large spaces for the larger nerve-cells and 

 fine passages for the nervous filaments. At the junction of the 

 grey matter with the white matter, the neuroglia of the one is 

 continuous with that of the other, and the connective tissue septa 

 of the latter run right into the former ; the outline of the grey 

 matter is not smooth and even, but broken by tooth-like processes 

 due to the septa. Since, as we have just said, some of the true 

 nerve-cells are very small, and since the nerve filaments like the 

 neuroglia fibres are very fine and take like them an irregular 

 course, it often becomes very difficult in a section to determine 

 exactly which is neuroglia and which are nervous elements. The 

 neuroglia cells may however be distinguished perhaps from the 

 smaller nerve-cells by their nuclei not being so conspicuous or so 

 relatively large as in a nerve-cell, and by their staining differently. 



The grey matter then may be broadly described as a bed of 

 neuroglia, containing a certain number of branching nerve-cells, 

 for the most part though not exclusively large and conspicuous, 

 but chiefly occupied by what is not so much a plexus as an 

 intricate interweaving of nerve filaments running apparently in 

 all directions. Some of these filaments are fairly conspicuous 

 naked axis-cylinders, and a few are easily recognized medullated 

 fibres of ordinary size ; but by far the greater number are either 

 exceedingly fine medullated fibres, whose medulla is only made 

 evident by special modes of preparation or delicate fibrils devoid 

 of medulla. With the nervous web formed by these filaments 

 the branching processes of the nerve-cells, on the one hand, and 

 the divisions of nerve-fibres passing into or out of the grey 



