384 SPECIAL HISTOLOGY. 



invariably lie with their sides parallel to the surface of the 

 lens, regularly interdigitating with each other by their acute 

 borders, so that, as is shown in fig. 306 2 , in the interior of the 

 lens, each tube is surrounded by six others, and their trans- 

 verse section presents the aspect of a wall built up of hexagonal 

 bricks. As the edges and corresponding surfaces of the tubes 

 are usually somewhat uneven, or even toothed (in animals, par- 

 ticularly Fishes, beautifully so) their lateral union is rendered 

 more intimate than it is between their broader surfaces, and on 

 this account also the structure is more readily torn into lamellae 

 in the direction of the surfaces, than into vertical plates in that 

 of its thickness. For the same reason also, a lamellar structure 

 may be assigned to the lens, as is commonly done, seeing that 

 it is constituted of concentric laminae like an onion, only it 

 must not be forgotten that these laminse are not regularly 

 defined layers, and never consist of a single stratum of tubes, 

 and moreover, what may prove of great physiological importance, 

 that the elements of the lens are, properly, still more regularly 

 disposed in the direction of its thickness, so that, throughout 

 the lens, they cover each other, and the latter might be re- 

 garded as consisting of very numerous vertical segments, the 

 thickness of which would correspond with the width of a single 

 fibre. [Bowman, 1. c, p. 69.] 



The course of the tubes of the lens in the separate lamellae is 

 in general such that both the superficial and the deeper, in the 

 centre of the lens, radiate towards the margins, and then 

 curve round upon the other surface, anterior or posterior, but 

 in such a way that no fibre extends through the entire semi- 

 circumference of the lens, or reaches, for instance, from the 

 middle of the anterior surface to that of the posterior. More 

 precisely described, the tubes on the anterior and posterior 

 surfaces of the lens do not proceed exactly to the middle, but 

 terminate in a stelliform figure which exists in that situation. 

 In the foetus and in the new-born child, each of these stelli- 

 form figures of the lens, which are readily seen by the naked 

 eye, presents three rays, which usually meet, regularly, at 

 angles of 120°; in the anterior star, two of the rays are directed, 

 the one upwards and the other downwards ; the reverse beiug 

 the case with the posterior " star," which, therefore, as com- 

 pared with the anterior, appears as it were turned round in an 



