ON EMBRYOLOGY AS AN AID TO ANATOMY 47 



regard the oblique muscles as involuntary, especially 

 the superior oblique, whose separate nerve supply 

 was supposed to be thus accounted for. However, 

 as Bell himself points out, this theory involves an 

 assumption which more recent research has failed 

 to verify. He showed that division of the superior 

 oblique muscle causes the upward rolling of the 

 eyeball to be increased, and that therefore if this 

 movement is due to an impulse transmitted along 

 the fourth nerve this impulse must be of such a 

 nature as to cause not contraction but relaxation of 

 the muscle i.e. t that stimulation of the fourth nerve 

 causes relaxation of the superior oblique muscle and 

 not contraction. 



I have referred to the views of Sir Charles 

 Bell for two very sufficient reasons : firstly, because 

 this is, so far as I am aware, the only rational 

 attempt that has been made to grapple with the 

 problem before us ; secondly, because any account 

 of such a question without reference to the opinion 

 of the great anatomist who did so much to render 

 it possible for us to understand problems connected 

 with the distribution of the nerves would be a gross 

 injustice. 



So far we have failed utterly to master our prob- 

 lem ; anatomy and physiology have alike failed to 

 give us the clue we require, and for my part I see 

 no reason why, if we had nothing else to help us, 

 this should not always be so, and the problem be 

 ranked as insoluble. It is under circumstances 

 such as these that the anatomist turns to embry- 

 ology that sheet-anchor of philosophical anatomy 



