CELLS CONNECTED TOGETHER. CORNEA. 



165 



lastic tissue, whilst the middle one, which forms its principal thick- 

 ness, is composed of white fibres interlaced together in such a manner 



Fig. 41. 



Nutrient Vessels of the Cornea; A, Superficial vessels belonging to the Conjunctival membrane, and 

 continued over the margin of the Cornea; B, Vessels of the Sclerotic, returning at the margin of the Cornea. 



as to form numerous lamellae, their interspaces or areolae having the 

 form of tubes regularly arranged and constricted at intervals, so as 

 not to be unlike rows of cartilage-cells, for which in fact they have been 

 mistaken. Two sets of vessels, a superficial and a deep-seated, surround 

 the margin of the cornea. The former (Fig. 41, A,) belong rather to 

 the Conjunctival membrane, which forms the outer layer of the cornea ; 

 and they are prolonged to the distance of l-8th or half a line from its 

 margin, then returning as veins. The latter (B) do not pass into the 

 true Cornea, but terminate in dilatations from which veins arise, just 

 where it becomes continuous with the sclerotic. In diseased conditions 

 of the Cornea, however, both sets of vessels extend themselves through 

 it. Notwithstanding the absence of vessels in the healthy condition of 

 the corneal tissue, incised wounds of its substance commonly heal very 

 readily, as is well seen after the operation for Cataract ; but there is a 

 danger in carrying the incision around a large proportion of its margin, 

 lest the tissue should be too much cut off from the supply of nutriment 

 afforded by the ampullae of the vessels that surround it. 



275. The Crystalline Lens of the Eye approaches Cartilage, in its 

 structure and mode of nutrition, more nearly than any other tissue. 

 It may be separated into numerous laminae; which are composed of 

 fibres that lock into one another, by their delicately-toothed margins. 

 Each of these fibres appears to be made up of a series of cells, linearly 

 arranged, which coalesce at an early period. The lens is not per- 

 meated by blood-vessels ; at least after it has been completely formed ; 

 these being confined to the capsule. During the early part of foetal 

 life, and in inflammatory conditions of the Capsular membrane, both 

 its anterior and its posterior portions are distinctly vascular ; but at a 

 later period, only the posterior half of the Capsule has vessels distri- 

 buted upon its surface. It has been shown by optical experiments 



