41 6 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



from red blood corpuscles, the nearest blood supply 

 being that of the sclerocorneal margin in the region 

 of the canal of Schlemm. 



Histologically the cornea is made up of five layers : 

 i, the anterior epithelium; 2, the anterior elastic 

 membrane, or Bowman's membrane; 3, the ground 

 substance, or substantia propria; 4, Descemet's 

 membrane; 5, the endothelium of Descemet's 

 membrane. 



The corneal epithelium is of the stratified squamous 

 variety, a little thicker near the corneal margin than 

 at its center and in the human eye is composed of five 

 layers of cells. It is related to the epidermis of the 

 skin, the cells being provided with short prickles 

 that are very difficult to demonstrate. This epithe- 

 lium forms an efficient and important protection to 

 the front of the eye. The anterior elastic membrane 

 measures 8 fi in thickness, about the width of a red 

 blood corpuscle, and becomes thinner towards the 

 sclerocorneal junction. It is a compact layer of con- 

 nective-tissue fibrils and is regarded by some as a 

 basement membrane to the overlying epithelium. 

 Nerve fibers penetrate this membrane to connect 

 with the corneal epithelial cells. The substantia 

 propria constitutes the bulk of the cornea. It con- 

 sists of bundles and lamellae of connective-tissue 

 fibrils, and peculiarly flattened cells called corneal 

 corpuscles. The fibrils of each lamella are cemented 

 together and run parallel to each other and to 

 the corneal surface, but so arranged that those of ad- 

 jacent lamellae cross at an angle of about twelve 

 degrees. 



The lamellae are also cemented to each other. The 



