142 [June 19, 



within them and around themselves a gradually increasing layer of 

 finely- granular substance. The thick cell-walls have all the ap- 

 pearance commonly assumed by connective tissue, and are continuous 

 with that tissue in the grey substance of the cord. 



In the intervertebral ganglia there is some difference in the man- 

 ner in which the nerve-cells make their appearance. The small cells 

 or nuclei gradually enlarge, assuming a variety of shapes ; and it is 

 not till they have increased to a considerable size that nuclei and 

 granular contents are observable within them. These cells, like those 

 of the cord, are connected, not only with eacli other, but with fibrous 

 prolongations from the sheath of the ganglion, with the intervening 

 connective tissue, and with the sheaths of blood-vessels, in one un- 

 interrupted network. The fibres of the posterior roots of the nerves, 

 as they pass through the ganglion, split up and subdivide into 

 fibrillse, which become successively continuous with processes of 

 series of the nerve-cells, which for the most part are cup-shaped or 

 pyriform. 



The processes of the epithelium around the canal of the cord are 

 directly continuous with the connective tissue and with the sheaths 

 of blood-vessels and pia mater at the surface. 



In the early stages of development, then, it appears that there are 

 two kinds of nuclei in the grey substance of the cord : that one kind 

 developes the general network of tissue which pervades the entire sub- 

 stance, but proceeds no further ; that each of the other kind, while it 

 is connected with this network, as well as with the true nerve-fibres, 

 developes around itself a nucleated wall, which is still connected, and 

 ultimately blended with the surrounding reticular structure, but, 

 proceeding further, it again forms around itself and within the cell- 

 wall an increasing layer of granules. The granular contents of 

 the cells are connected with their walls, which they form around 

 themselves ; the walls of the cells are continuous with the connective 

 tissue, and this again is continuous with the sheaths of the blood- 

 vessels and pia mater of the surface, as well as with the processes of 

 the epithelium : so that the connective tissue of the cord would 

 appear to be intermediate in its nature between the nerve-tissue and 

 the pia mater on the surface ; but there is no reason to believe that 

 the connective tissue could ever be developed into nerve-tissue. 



