THE EYE. 



407 



line membrane. The corneal substance consists o£ flat bundles 

 of fibres arrang-ed in laminae, with cement-substance and connec- 

 tive-tissue corpuscles interposed. The fibrils are extremely fine 

 (o'oooi mm., Engelmann), and bound together into bundles by 

 cement-substance. The bundles of the laminae are arranged at 

 various angles, though many are placed at right angles to each 

 other (Waldeyer). 



Between the laminae are flattened spaces, which seen in section 

 are spindle-shaped. By proper treatment they are seen to be irreg- 

 ular, branched spaces, 

 which communicate 

 by fine canals and 

 form part of the Reek- 

 linghausen-canals or 

 lymph-system. These 

 spaces contain branch- 

 ed, connective-tissue 

 corpuscles (Toynbee), 

 and a colourless fluid. 

 The corpuscles (Fig. 

 254 e) do not fill the 

 spaces which they 

 occnjiy. They possess 

 large nuclei, sur- 

 rounded by granular 

 protoplasm. 



The canals by which 

 these spaces communicate (' Saftcanalchen ■■ of Recklinghausen) lie, 

 in general, parallel to the surfaces of the cornea, and communi- 

 cate by joining at acute angles or by short transverse branches. 

 According to Lavdowsky, these canals have a distinct lining 

 membrane. 



The anterior hyaline ^ layer (Bowman^s or Reichert^s lamella) is 

 not so well seen in the frog as in some higher animals ; it is simply 

 a portion of the corneal substance, of somewhat denser structure 

 than the rest, into which it passes by a gradual transition. 



(4) The posterior hyaline membrane (Descemet's membrane) 

 is a highly elastic, very transparent layer, placed behind the 

 true corneal substance ; in the frog some few bundles of fibres 



* Tamanscheff and Schweigger-Seidel consider the anterior and posterior hyaline 

 membranes to be composed of fine fibrils. 



riepaiation from cornea of Rana escitlenta ; after Klein. 

 Hartnack's Syst., Obj. VII, Oc. 3. 

 a Nerve of first order. 

 6 Nerve of second order. 

 c Nerve of third order. 

 d Nerve of fourth order. 

 e Corneal corpuscles. 



