THE EYE AND THE PHYSIOLOGY OF VISION. 



545 



into it posteriorily. The exact movements which each of 

 these muscles is able to produce may be readily seen from 

 their manner of attachment. 



One of the most striking things about these muscles is 

 the harmony with which they work. In normal eyes the co- 

 ordination is almost perfect. When, however, one or more 

 of these muscles cease to be so carefully adjusted, either as 

 a cause of paralysis or of other causes, there results what is 

 familiarly called the "squint,' 7 which is a right or a left, an 

 external or internal squint, according to the muscle affected. 

 An exaggerated condition of a squint is finally termed 

 "cross-eyed." 



Fig. 169. SEMIDIAGRAMMATIC SECTION OF THE EYEBALL. 

 (The reader will find the explanation of the section in the text.) 



5. The Globe of the Eye. The globe of the eye is a 

 spherical body an inch or more in diameter, with a large 

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