752 SPECIAL HISTOLOGY. 



lie with their sides parallel to the surface of the lens, regularly inter- 

 digitating with each other bj their acute borders, so that, as is shown 

 in Fig. 306 ^, in the interior of the lens, each tube is surrounded by six 

 others, and their transverse section presents the aspect of a v«'all built 

 up of hexagonal bricks. As the edges and corresponding surfaces of 

 the tubes are usually somewhat uneven, or even toothed (in animals, 

 particularly Fishes, beautifully so) their lateral union is rendered more 

 intimate than it is between their border 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 laminge 

 like an onion, only it must not be forgotten that these laminae 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 regarded as consisting of very 

 numerous vertical segments, the thickness of which w^ould correspond 

 with the width of a single fibre. [Bowman, 1. c, p. 69.] 



The coarse of the tubes of the lens in tlie separate lamellce 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 stelliform 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 down- 

 wards ; the reverse being the case with the posterior "star," which, 

 therefore, as compared with the anterior, appears as it were turned 

 round in an arc of 60°. Now, the tubes arising from the middle of the 

 anterior "star" extend, on the posterior aspect, only as far as the 

 extremities of the three rays; and, on the other hand, those comraen- 

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

 Similar conditions obtain in all the tubes situated between these two 

 points, so that none of them reach entirely round ; and all the tubes in 

 a layer are of equal length. Now precisely the same thing also exists 

 in the "nucleus" of the lens in the adult, whilst in the superficial 

 lamellce, and on the surface itself, we observe a more complex "star," 



