MOTOR OCTJLI COMitUfflS. 131 



all of the muscles, particularly the four recti, act to draw 

 the globe into the orbit, which allows the lid to fall slight- 

 ly, and projects the little membrane which serves as a third 

 eyelid in these animals. 



Observations with regard to the influence of the third 

 nerve upon the movements of the iris have not been so sat- 

 isfactory in their results as those relating to the muscles of 

 the eyeball. It will be remembered that this nerve sends a 

 filament to the ophthalmic ganglion of the sympathetic, and 

 that from this ganglion, the short ciliary nerves take their 

 origin and pass to the iris. The ganglia of the sympathetic 

 system receive branches both from motor and sensory nerves 

 belonging to the cerebro-spinal system, and the ophthalmic 

 ganglion is no exception to this rule. While it is undoubt- 

 edly true that division of the third nerve affects the move- 

 ments of the iris, it becomes a question whether this be a 

 direct influence, or an influence exerted primarily upon the 

 ganglion, not, perhaps, differing from the general effects 

 upon the sympathetic ganglia that follow destruction of 

 their branches of communication with the motor nerves. 

 As yet we know little of the reciprocal influences of the 

 cerebro-spinal and the sympathetic system; but some of 

 the researches of Bernard into the influence of the sym- 

 pathetic ganglia upon the salivary secretion show that the 

 submaxillary ganglion, at least, becomes paralyzed, -or loses 

 its influence over the secretion of the submaxillary gland, 

 after it has been separated for a certain time from the cere- 

 bro-spinal system. 1 These considerations, however, belong 

 more properly to the sympathetic system. 



The most important experimental observations with re- 

 gard to the influence of the third nerve on the iris are the fol- 

 lowing : Herbert Mayo made experiments on thirty pigeons, 

 living or just killed, upon the action of the optic, the third, 

 and the fifth nerves on the iris. He states that when the 



1 BERNARD, Recherches experimentales sur les nerfs vasculaires et calorifiques. 

 Journal de la physiologic,, Paris, 1862, tome v., p. 409. 



