SYMPATHETIC GANGLIA 251 



THE CHICK 



Ciliary ganglion 



Detailed observations on the development of the ciliary gan- 

 glion in the chick are recorded by Carpenter ('06) in the paper 

 referred to in an earlier section of this paper. Earlier observations 

 on the development of this ganglion in birds are reviewed also by 

 this author and will not be further considered in the present paper. 



According to Carpenter's observations, the ciliary ganghon arises 

 in embryos of the chick during the fourth day of incubation as a 

 slight accumulation of cells in the path of the oculomotor nerve. 

 The fibers of the oculomotor nerve are, from their earhest ap- 

 pearance, accompanied by cells obviously of nervous origin. Car- 

 penter has designated these elements as 'accompanying' cells 

 and interprets them as cells of medullary origin which have 

 wandered out from the mantle layer in the wall of the mesenceph- 

 alon into the root of the oculomotor nerve and advanced periph- 

 erally along its fibers. Some of these cells become aggregated 

 in the path of the oculomotor nerve and give rise to the anlage 

 of the ciliary ganglion. Many of the ' ' accompanying ' ' cells under- 

 go division by mitosis along the path of the nerve as well as in 

 the anlage of the ciliary ganglion. During the fifth day of incu- 

 bation, many of the cells in this ganglionic anlage become differ- 

 entiated into neuroblasts. Some of them give rise to supporting 

 elements. 



During the earlier stages of development , according to Carpen- 

 ter, the ciliary ganglion is not connected with the ophthalmic 

 division of the trigeminal nerve and receives cells only via the oculo- 

 motor nerve. As development advances, cells which have ad- 

 vanced peripherally from the Gasserian ganglion along the oph- 

 thalmic nerve advance into the ciliary ganglion along the path 

 of the fibrous ramus which grows from the ophthalmic nerve 

 into the latter. The number of cells w^hich enter the ciliary 

 ganglion from this source, however, is relatively small. The 

 ciliary ganglion, therefore, arises primarily from cells which ad- 

 vance peripherally from the wall of the mesencephalon along the 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 24, NO. 3 



