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EXPERIMENTAL PHYSIOLOGY. 



tached to the processes of the posterior surface of the ciliary body as far back as 

 the ora serrata of the retina. The contents of the eyeball are under a pressure 

 which is greater than atmospheric by about 25 cms. Hg. They therefore press 

 outwards on the coats of the eyeball and as a result of this the choroid coat and 

 the ciliary body, its forward continuation, pressed out by the vitreous humour, 

 pull backward as well as outward on the lens ligament. This in its turn exerts 

 more pull on the anterior than it does on the posterior surface of the lens capsule. 

 The lens itself is fluid in nature and its capsule is elastic. Its natural shape is a 



Corn-* 



FIG. 43. Diagram of the attachments of the lens, and of the neighbouring structures. 



more or less rounded one but, being flexible, it yields to the pull of the ligament 

 and both its surfaces are flattened, the anterior however much the more so. 

 The act of accommodation is a contraction of the circular and radial muscle 

 fibres which are contained in the ciliary body. This makes the circle of the 

 free margin of the body smaller, brings it nearer to the lens, and causes the 

 processes of the posterior part to move forward, dragging with them the anterior 

 part of the choroid, with which they are continuous. The fibres of the ligament 



