172 bulletin: museum of comparative zoology. 



ing at its base, and no cells were intermingled with its fibres. About 

 its periphery was a thin envelope, formed by a single layer of mesoder- 

 mal cells. Later, the nerve was observed to have descended to the 

 ventral face of the brain. 



His ('80, '88, '88^ ) maintains that the ciliary ganglion develops in 

 man from the anterior portion of the first ganglionic or trigeminal com- 

 plex of the head, which is a direct descendant of the neural crest. He 

 does not accept the distinction made by Beard ('87) between a raeso- 

 cephalio and a ciliary ganglion, but asserts that the ganglion which 

 Eemak, himself, and so many others Jiave seen at the anterior extremity 

 of the neural crest, is identical with the long-known ciliary ganglion. 

 In opposition to Schwalbe, he assigns this ganglion to the fifth rather 

 than to the third nerve, since it develops over the fore-brain, while 

 the third nerve grows out from the ventral face of the pid-hrain. 

 Furthermore, the oculomotor arises as a purely motor nerve, and, as 

 isuch, is not entitled to a ganglion. 



Both the third and sixth nerves arise in human embryos as fibrous 

 'outgrowtlis of neuroblasts situated in the ventral zone of the medullary 

 wall, not far from the median plane. 



It is stated in Quain's Anatomy ('95, Thane, p. 388) that Martin 

 i('90) found a dorsal root of the oculomotor nerve in an embryo cat. 

 The original article has not been accessible. 



His, Jun. ('91) compared, in an embryo cat, the cells of a cerebro- 

 spinal, a sympathetic and the ciliary ganglion. In the first, he found 

 large, bipolar cells, and in the sympathetic and ciliary ganglia, small, 

 unipolar cells. 



Chiarugi ('94, '97) observed the oculomotor nerve, in the youngest 

 guinea-pig embryos in which it was present, springing from the ventral 

 side of the mid-brain, near the median plane. On the trunk of the 

 nerve, close to the root, he discovered a rudimentary ganglion. Since 

 no ganglion cells were to be seen along the further course of the nerve, 

 between the ganglion and the place of connection with the ophthalmic 

 branch of the trigeminus, he considers it improbable that the ganglion 

 owes its origin to nervous elements which have passed from the trigem- 

 inus to the oculomotor. In the wall of the brain there were to be seen, 

 however, several neuroblasts, lying along the root fibres of the third 

 nerve, and, apparently, advancing to the free surface. This leads him 

 to the supposition that the cells of tlie ganglion are derived through 

 migration from the brain wall. He believes that this ganglion has no 

 connection with the ciliary ganglion, which develops later in close re- 



