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bulletin: museum of comparative zoology. 



to either the cerebrospinal or sympathetic systems, it is plain that the 

 two regions described above must be separately considered. In respect 

 to the first or ventral region (B), it can be said that the size of its cells, 

 the heavy medullation of botli its central and peripheral neuraxons, 

 and the comparatively small volume of the pericellular fibrils, agree 

 with the conditions found in cerebro-spinal ganglia. The central and 

 peripheral neuraxons are, however, of smaller calibre. It is probable 

 that the large bipolar ganglion cells obtained by maceration methods, 



rm. opth. trig. 



rm.comn.. 



rm. comn: 



sm. V: 



Diagram of a longitudinal section through the ciliary ganglion. A, region of small cells, 

 non-medullated neuraxons, and pericellular fibrils; a, small, non-medullated ciliary 

 neuraxons; B, region of large cells and small medullated neuraxons; P, small, medullated 

 ciliary neuraxons; n. ciL, ciliary nerve; n. oc'mot., oculomotor nerve (large and small 

 medullated neuraxons); rm. comn., communicating ramus (small non-medullated neu- 

 raxons); rm. comn.', distal neuraxons of communicating ramus; rm. comn.", recurrent 

 neuraxons of communicating ramus; rm. opth. trig., ophthalmic branch of trigeminal 

 nerve ; rm. v., ventral ramus (large and small medullated neuraxons). 



as already described, were from this region. These resemble cerebro- 

 spinal elements, except that two medullated processes instead of one 

 are given off by each cell ; and even where a tendency toward uni- 

 polarity occurs, the typical T-shaped condition of a cerebro-spinal 

 neuron is not attained. 



In the second or dorsal region (A) of the ciliary ganglion, the small- 

 ness of the cells, the absence of heavily medullated processes, and the 

 comparative abundance of pericellular fibrils, suggest a sympathetic 

 ganglion. Moreover, the resemblance is strengthened by the entrance 



