150 BULLETIN : MUSEUM OF COMPARATIVE ZOULOGY. 



motor chain, and consequently sympathetic in their relations. The 

 muscles innervated are of the unstriped variety. 



Stefani (:01) was led to the conclusion that the short ciliary nerves 

 have their centres, i. e., their ganglion cells, in the ciliary ganglion, by 

 observing the effect on the cells of that ganglion when atropin is applied 

 to the eye. 



Histologically, the ciliary ganglion of birds differs from that of mam- 

 mals. In the hen certain of its cells, as was first shown by Retzius ('81), 

 are bipolar in character, each sending out two processes, which arise 

 close together, and run either in the same or in opposite directions. 

 Near their origins from the cell the processes are pale, but soon acquire 

 medullary sheaths. Holtzmann ('96) examined the elements of the 

 ciliary ganglion in the hen, duck, goose, and pigeon, finding in each of 

 the four species both large and small ganglion cells. These were usually 

 bipolar, but an occasional unipolar cell was observed, the single process 

 of which soon divided into two. Holtzmann is of the opinion that while 

 in many animals (amphibians, mammals) the ciliary ganglion contains 

 both sympathetic and spinal cells, in birds a one-sided development, 

 that of spinal elements, takes place. These do not, as a rule, become 

 fully differentiated into true unipolar spinal ganglion cells, but remain 

 in an embryonic bipolar condition. 



From the foregoing, it is apparent that those cells of the ciliary gan- 

 glion of birds which have been described by investigators do not resemble 

 histologically the sympathetic cells found in the same group. The great 

 majority of the latter are well known to be multipolar, and, in general, 

 to resemble the sympathetic cells of mammals (Ramon y Cajal, '91, '94; 

 Timofeew, '98; Huber, '99). 



Physiological Evidence. From a physiological point of view the ciliary 

 ganglion of mammals is undoubtedly sympathetic. The experimental 

 researches of Langley and Dickinson ('89) have demonstrated the fact 

 that a moderate dose of nicotin, which has little, if any, effect on spinal 

 ganglia, prevents the passage of efferent nervous impulses through sym- 

 pathetic ganglia. These authors considered this result due to a paralysis 

 of the sympathetic cells, but Huber ('97) has shown that it is more 

 probable that the nicotin paralyzes the pericellular baskets of the pre- 

 ganglionic neuraxons about the cells, rather than the cells themselves. 

 The physiological effect of nicotin has afforded, therefore, a valuable cri- 

 terion for determining the character of the cells of the ciliary ganglion. 

 After an injection of nicotin, Langley and Anderson ('92) found that 

 the ciliary ganglion of the rabbit no longer transmitted nervous impulses. 



