174 SENSORIAL ^UNCTION &r 



draw the eye forwards, serving as antagonists to the 

 straight muscles. The upper oblique muscle s 9 is very 

 remarkable for its anatomical structure. Its tendon 

 passes through a little aperture in a piece of cartilage, 

 which is fastened to the upper margin of the orbit. 

 The tendon then turns back, forming a complete pulley, 

 and is inserted into the upper side of the eye-ball as 

 seen in the figure. It is obvious that the effect produc- 

 ed by the contraction of this muscle, is exactly contrary 

 to that of the action of its fibres. 



This muscle affords another instance of that simplicity, 

 effect and design, which we so often meet with in the 

 study of nature, and especially in the mechanism of the 

 human frame. Taking the contiguous parts as they are, 

 in no other situation could this muscle have been placed, 

 without interfering with the action of some other part, nor 

 could any other construction, occupying the^ same limit- 

 ed space, have been devised to answer the same pur- 

 pose, being made to pull in a direction contrary to its 

 own action. 



MAGNITUDES AND DISTANCES OF OBJECTS. 



An inquiiy into the philosophy of vision for the purpose 

 of ascertaining in what manner we are able to appreciate 

 the distance of an object by its apparent magnitude, to- 

 gether with the subject of perspective, and the phenomena 

 of vision generally, would lead us far beyond the limits 

 of this work. We will however cite two or three 

 curious cases, in order to show how far we are able to 

 gain a knowledge of the forms, magnitudes, and distan- 

 ces of things without the aid of the eyes. So far as 

 any of us can remember, we have always been able to 

 form a judgment of the forms, distances, and magnitudes 

 of objects, by the eye, and especially with respect to 

 those which are not at very remote distances. But 

 how far these distances are appreciated by walking from 



Describe the upper oblique muscle of the eye, and show its use ? 

 What is said of the mechanism of these muscles 7 



