carpenter: development of the oculomotor nerve. 157 



glia present a quite different appearance. Tlie cells of these are unob- 

 scured, and their boundaries are sharply defined. 



When the ciliary ganglion of the hen is prepared according to the vom 

 Eath process, and sectioned longitudinally, it is seen, under the micro- 

 scope, to be divisible into two regions (compare A and B, text Figure). 

 Approximately two-thirds of tlie ganglion {B) is composed niaiuly of 

 large, well-defined cells, around which very few pericellular fibrils occur. 

 Some of these cells reach the dimensions of the largest of the spinal- 

 ganglion cells. In this portion of the ganglion are found small, but 

 heavily niedullated, neuraxons. Of these, a part are evidently continu- 

 ous with the neuraxons entering the ganglion from the oculomotor nerve. 

 Others are plainly seen to leave the ciliary ganglion by the ciliary nerve, 

 the greater part of which arises from this portion of the ganglion, and is 

 made up of small, well-medullated neuraxons. 



In the dorsal region of the ciliary ganglion, on the side toward the 

 ophthalmic branch of the fifth nerve, qccurs an accumulation (^) of 

 small cells, which makes up approximately one-third of the entire volume 

 of the ganglion. Here are found fine neuraxons, showing little evidence 

 of medullation, and a quantity of delicate fibrils resembling those of the 

 pericellular baskets of sympathetic ganglia, although not present in such 

 profusion as in the sympathetic ganglia. A communicating ramus 

 between the ophthalmic branch of the trigeminus and the oculomotor 

 ciliary nerve has been mentioned. Longitudinal sections of the ciliary 

 nerves show that the slender, very slightly niedullated neuraxons which 

 compose the communicating ramus divide into two sets upon reaching 

 the ciliary nerve. One of these bundles turns toward the eyeball, and 

 accompanies the ciliary nerve to its peripheral distribution. The other 

 bundle is recurrent, being deflected toward the ciliary ganglion. Its 

 neuraxons run parallel with those of the ciliary nerve, and enter that 

 portion of the ganglion which is characterized by small cells and peri- 

 cellular fibrils. From this region there is given off to the eyeball a 

 bundle (a) of fine neuraxons with but slight traces of medullation. 

 These accompany the medullated neuraxons from the remaining two- 

 thirds of the ganglion {fi) as component elements of the ciliary nerve. 

 In certain cases they may be found occurring in the form of a distinct, 

 non-meduUated bundle, running close beside the larger group of medul- 

 lated neuraxons, but separated from the latter by perineurium. 



The relations of the two parts of the ciliary ganglion are shown in a 

 diagrammatic way in the accompanying figure. 



In any attempt to assign the ciliary ganglio:i, on histological grounds. 



