568 



STRUCTURE OF THE LENS. 



[sect. 227. 



terior) surface, but in such a manner that no fibre traverses the 

 entire semi-circumference of the lamella; never reaches, for in- 

 stance, from the middle of the anterior to the middle of the pos- 

 terior surface. More accurately described, the tubes on the anterior 

 and posterior surfaces of the lens do not go exactly to the middle, 

 but terminate at two stellate figures, situated on the two aspects of 

 the lamella. In the foetus and in the newly-born infant, each of 

 these stars, which are visible to the naked eye, has three rays, 

 meeting each other regularly at angles of 120 ; in the anterior 

 star, two rays are situated below, one above ; the reverse in the 

 posterior star, which, accordingly, compared with the anterior, 

 appears as if turned round through an angle of 6o°. It will be 

 seen, therefore, that the fibres of the lens, which proceed from the 

 middle of the anterior star, run on the posterior side only as far as 

 to the extremities of the three rays ; and, vice versa, those starting 

 from the posterior pole do not reach the middle of the anterior 

 star; the same condition is presented in all the tubes situated 

 between these two points, none of them going quite round, and all 

 those which lie in one layer being of equal length. In the adult, 

 the nucleus of the lens presents exactly the same condition; but, 

 on the other hand, in the superficial lamellae, and on the surface 

 itself, a more compound star is found, having from nine to sixteen 



Fig. 23G. 



Lens of the adult, after Arnold, to show the stars. 1. Anterior surface ; 2. posterior surface. 



rays of various lengths, and rarely quite regular; still, however, 

 certain main rays may even here be distinguished from the others. 

 The course of the fibres necessarily becomes more complicated by 

 this means; and the more so, as on such scars the fibres attached 

 to the side of the rays converge in an arcuate manner, giving rise 

 to a penniform or whorled appearance (vortices lentis). But, 



