450 



THE EYE. 



from true connective-tissue fibers (Morochowetz), but are doubly 

 refracting, although the cornea as a whole yields chondrin and not 

 glutin on boiling. There are about sixty lamellae in the human 

 cornea. The fibrils composing each lamella are cemented together 

 and run parallel to one another as well as to the surface of the 

 cornea, but they are so arranged that the fibrils of each lamella 

 cross those of the immediately preceding one at an angle of about 

 twelve degrees. The lamellae themselves are likewise closely 

 cemented to one another. The most superficial lamella, lying im- 

 mediately beneath the anterior elastic membrane, is composed of 

 finer fibers, the course of which is oblique to the surface of the 

 cornea. Between the anterior and posterior elastic membranes are 

 bundles of fibers, which perforate the various lamellae of the cornea 

 and are consequently known as the perforating or arcuate fibers. 

 Between the lamellae are peculiar, flattened cells, possessing 



Lymph-canaliculi. 



! 



Corneal space. 



Fig. 354. Corneal spaces of a dog ; X 6 4- 



irregular or lamella-like processes, the fixed corneal corpuscles ; 

 these lie in special cavities in the ground substance of the substantia 

 propria, which are known as corneal spaces. In these spaces there 

 are also found a varying number of leucocytes. By means of vari- 

 ous methods (silver nitrate and gold chlorid treatment), these corneal 

 spaces may be shown to be part of a complicated lymphatic system, 

 comparable to the lymph-canalicular system of fibrous connective 

 tissue. This system of canals is also in communication with the 

 lymph-channels at the corneal margin. 



The posterior elastic or Descemet's membrane is not so inti- 

 mately connected with the substantia propria as Bowman's mem- 

 brane. It is thinnest at the center of the cornea, and becomes 

 thicker toward the margin. It may be separated into finer lamellae, 

 is very elastic, resists acids and alkalies, but is digested by trypsin. 



