156 bulletin: museum of compaeative zoology. 



nerve, a few small neuraxons occur among the larger ones. The nerve 

 trunk closely resembles in appearance that of the oculomotor, except 

 that a peripheral zone of small neuraxons is not present. 



The branch given off to the muscles of the nictitating membrane is 

 composed almost entirely of neuraxons of large size. 



3. Ciliary Ganglion. 



The cells obtained from the ciliary ganglion by maceration and iso- 

 lation answer to the description of the ciliary cells of the hen already 

 given by Retzius ('8l). They are large bipolar cells, the processes of 

 which become heavily meduUated a short distance from the cell body 

 (Plate 2, Fig. 4). In a few instances the two neuraxons were seen to 

 arise by a common stem, so that the ganglion cell may be said to be 

 unipolar in character. 



With the object of comparing the finer structure of the ciliary gan- 

 glion with that of cerebro-spinal and sympathetic ganglia, attempts were 

 made to obtain an intra-'vitam methylen-blue stain. Three trials were 

 made, but in only one of these were the cells of the ciliary ganglion 

 affected. The cells in this instance were not, however, deeply stained, 

 and no pericellular baskets of fibrils were differentiated about them, 

 such as have been demonstrated about the sympathetic cells of birds 

 by Huber ('99) after injection of methylen-blue into the blood 

 system. 



Such evidence as I have been able to obtain as to the sympathetic or 

 cerebro-spinal nature of the ciliary ganglion has resulted from the use of 

 the vom Rath mixture. After fixation in this reagent, sections of spinal 

 ganglia can with ease and certainty be distinguished from sections of sym- 

 pathetic ganglia. Spinal cells average larger, some measuring as much 

 as 60 micra in diameter. Cells of this size are never found in sympathetic 

 ganglia. Large meduUated neuraxons are given off by spinal cells, and 

 portions of these occur in every section through the ganglia. The periph- 

 eral neuraxons of the sympathetic cells, though also meduUated, are 

 never of as large calibre as those of the spinal cells. But the most 

 convincing/ and characteristic peculiarity of the sympathetic ganglia is 

 the mass of fine fibrils which occurs in them, filling in the interstices 

 between the cells, and obscuring, to some extent, their boundaries and 

 cytoplasm. Though their relations to the cells are not well brought out 

 by the vom Eath stain, these fibrils undoubtedly form the pericellular 

 baskets which are known to be present in sympathetic ganglia. Owing 

 to the absence of such an abundance of fibrous elements the spinal gan- 



