SECT. 227.] 



CRYSTALLINE LENS. 



567 



Lenticular tubes or fibres. 1. Of the ox, with 



slightly den tated margins ; 2. transverse section of 

 the lenticular tubes of man. Magnified 350 times. 



cannot be demonstrated as true tubes. Their union is effected by 

 simple apposition, their Hat Fig. 235. 



surfaces invariably lying 

 parallel to the surface of 

 the lens, and their attenu- 

 ated borders locking regu- 

 larly into each other; in 

 the interior of the lens, 

 therefore, as seen at fig. 235, 

 2, every tube is surrounded 

 by six others, and their 

 transverse sections present 

 the appearance of a wall 

 built of six-sided bricks- 

 At their borders, and the 

 surfaces of the borders, the 

 tubes are generally some- 

 what uneven, or are even 

 toothed (in animals, espe- 

 cially fish, very much so) , so 

 that the union of them, side 

 to side, is more intimate than that of their broader surfaces ; and 

 it is on this account, also, that the lens breaks up into lamellae 

 more readily in the direction of the surface than in that of the 

 thickness. In consideration of this peculiarity, we may ascribe a 

 lamellated structure to the lens, which is the usual manner of 

 describing it, and we may regard it as consisting, like an onion, of 

 a series of laminae, one enclosed within the other \ we must not, 

 however, lose sight of the fact, that these laminae are not regularly- 

 bounded layers, and that they never consist of a single layer of 

 tubes ; we must also remember, as being perhaps of great physio- 

 logical importance, that the regularity of disposition in the elements 

 of the lens is, properly speaking, still more observable in the di- 

 rection of the thickness of the lens, than in the direction of its 

 breadth. These elements, indeed, cover each other accurately 

 throughout the whole lens; and the latter may equally Avell be 

 regarded as consisting of very numerous perpendicular segments, 

 each having the breadth of a single fibre. 



The course of the tubes of the lens in the individual lamella is, 

 in general, the following : they radiate, both in the superficial and 

 in the deeper portions, from the axis of the lens towards the 

 borders, and then curve round to the opposite (anterior or pos- 



