606 



PHYSIOLOGY 



the curvatures of its surfaces again. It will be found that, as soon 

 as the lens is free from its attachments in the eyeball, the curvature of 

 its anterior surface is increased. The change therefore in the lens, 

 which is responsible for the alterations in its refractive power deter- 

 mining accommodation, may be effected by any means which will 

 relax the suspensory ligament, such, for instance, as approximation 

 of the ciliary processes to the margin of the lens. This movement of 



FIG. 270. Diagram of mechanism of accommodation. (TIGEBSTEDT 

 after SCHON.) 



The dotted line shows the form of the lens during accommodation for 

 near objects. 



the ciliary processes is effected by the ciliary muscle. The attach- 

 ments of this muscle are shown in Fig. 269. It forms a circle of 

 unstriated muscle fibres, triangular in cross-section, and extending 

 round the whole circumference of the eyeball. The fibres of the muscle 

 are divided into three groups : 



(a) The meridional fibres, which run from the corneo-sclerotic 

 junction backwards and outwards to be attached to the anterior part 

 of the choroid coat behind the ciliary processes. 



(b) The radial fibres, which pass from the margins of the canal of 

 Schlemm, and from the fibres of the ligamentum pectinatum to be 

 attached behind to the whole extent of the ciliary processes. 



