216 DR J. 0. WAKELIN BAERATT. 



in fig, 1, between levels forty-eight and fifty-seven on the 

 millimetre scale, and by the similar diagram in fig. 2 at the 

 levels forty-nine to fifty-seven. 



Turning now to a study of the nerve in transverse section, it 

 is found (figs. 1 and 2) that the rootlets of origin (which from 

 their number and complexity cannot be individually represented 

 in sections ten, fifteen, and twenty) become more and more 

 closely bound together when the nerve receives its fibrous 

 sheath, until in section thirty-five the nerve presents a fairly 

 uniform appearance, with very few septa. Shortly afterwards 

 the two main divisions of the nerve appear, the superior almost 

 immediately, and the inferior a little later, breaking up into 

 terminal bundles, which enter the various muscles which they 

 supply. 



The superior division of the 3rd nerve is seen to form the 

 outer portion of the main trunk, while the inferior division forms 

 the inner part (fig. 1). The amorphous material lying among 

 the nerve fibres (fig. 1, vest. dr. ; fig. 2, v.s.) is situated in the 

 inferior division, whence also the short root of the ciliary 

 ganglion arises. 



The nerve fibres of the 3rd cranial nerve consist, at its 

 origin in the cavernous sinus (levels eighteen to thirty-five, fig. 2), 

 and in the various branches of the upper and lower divisions, of 

 large medullated fibres, having a diameter of 11/x to 15/x, and of 

 small medullated fibres, 3^ to 5^ in diameter (fig. 3, a, h, c). The 

 proportion between the two varies somewhat in different places 

 in the same section, but generally speaking there are nearly 

 three times as many large medullated as small. In the situation 

 of the amorphous granular material already referred to, namely, 

 near the superficial origin of the nerve, small medullated fibres 

 are rather numerous. The short root of the ciliary ganglion 

 consists chiefly oF small medullated fibres oij. in diameter, only a 

 small number of larger medullated fibres, ^/j. in diameter, being 

 met with. The small medullated fibres in the short root of the 

 ciliary ganglion are fairly uniform in size. The fibres of the 

 ciliary nerves are of the same size, or slightly larger than those 

 in the short root ; they are mostly small medullated fibres, 3^ to 

 6/x in diameter, but larger fibres, 7/* to 11/x, in diameter, are also 

 present. The nerve-fibres in the long roi)t of the ciliary 



