212 bulletin: museum of comparative zoology. 



easily distinguished from the latter by reason of the larger size of their 

 nuclei and the greater abundance of their cytoplasm. A comparatively 

 small number of the ophthalmic ganglion cells migrate into the fundament 

 of the ciliary ganglion, passing at first through the mesenchyme, and 

 later along the neuraxons of a communicating ramus, which grows from 

 the ophthalmic branch of the trigeminus to the fundament of the ciliary 

 ganglion. In their origin from a cerebro-spinal ganglion, and in their 

 capacity for locomotion, these cells resemble those which, in the trunk 

 region, give rise to sympathetic ganglia. Of the ganglion cells migrating 

 along the ophthalmic branch, those which fail to reach the ciliary ganglion 

 are in part accumulated to form one or more transitory ganglia in the 

 distal portion of the nerve. By the end of the fifth day the transitory 

 ganglia, and nearly all the migrant ganglion cells distributed along the 

 nerve, have disappeared. 



3. In the adult fowl the ciliary ganglion is situated directly upon 

 the oculomotor nerve without the intervention of a radix brevis. Two 

 regions are distinguishable in the ganglion, a smaller dorsal region and a 

 larger ventral one. The first region presents many sympathetic charac- 

 ters, containing, as it does, small ganglion cells, slightly medullated 

 neuraxons and many pericellular fibrils. It receives neuraxons of 

 small calibre through the communicating branch from the trigeminus. 

 The communicating branch resembles histologically a ramus communi- 

 cans of the sympathetic system. From this region of the ganglion 

 practically non-rued ullated neuraxons proceed to the eyeball in company 

 with the other neuraxons constituting the oculomotor ciliary nerve. 

 This portion of the ciliary ganglion may have arisen from the migrant 

 ophthalmic cells which enter the fundament of the ganglion during de- 

 velopment. The larger ventral region of the ganglion contains large 

 cells, fine but well-medullated neuraxons, and few pericellular fibrils. 

 From this region are doubtless derived the large bipolar ganglion cells 

 with medullated processes which are to be obtained from the ciliary 

 ganglion by maceration methods. The greater part of the oculomotor 

 ciliary nerve passes out from this portion of the ganglion in the form of 

 a large bundle of fine medullated neuraxons. It is probable that the 

 cells of this region had their origin in the migrant cells from the embrv- 

 onic neural tube. 



4. The oculomotor ciliary nerve passes from the distal end of the 

 ciliary ganglion to the intrinsic muscles of the eye. It comprises fine, 

 well-medullated neuraxons together with a small number of neuraxons 

 with little if any medullation. In its course through the orbit it. gives 



