HISTOLOGICAL DEMONSTRATIONS. 129 



b. The nerves and connective corpuscles of the cornea may be 

 stained with gold chloride, as described in 330, a. 



c. The cell spaces amidst the corneal fibres may be readily demon- 

 stated as follows : * The epithelium is scraped away from the anterior 

 surface of the cornea of a living frog anaesthetised by chloroform, or 

 stunned to prevent all pain, and one or two drops of a 2 per cent 

 solution of nitrate of silver are introduced within the conjunctiva. At 

 the end of fifteen minutes the cornea is excised, placed in glycerine, and 

 exposed to diffuse daylight till it is of a brown colour. The cornea 

 may be split into layers with scissors and forceps. This will be found 

 advantageous, for the transparency of the cornea is greatly diminished 

 by silvering, and the outer layers are rendered useless by the process. 

 The preparations are mounted in glycerine. Such preparations may 

 also be made from the cornea of the rabbit, anaesthetised with ether. 



233. Structure. V. S. chromic acid cornea of cat, 

 prepared as stated in 232, a. Mount in Farrants' solution, 

 and examine. 



(L.) Anterior epithelium, Fibrous tissue. Elastic lamina 

 with posterior epithelium. Unless the section be made by 

 freezing, the posterior epithelium is very apt to be torn off. 



(H.) Several layers of the anterior epithelium, the lower 

 cells resting immediately upon the fibrous tissue without the 

 intervention of a thin elastic lamina Bowman's membrane 

 as in the case of the human cornea. 



The single layer of epithelium placed posteriorly on the 

 membrane of Descemet a thick elastic lamina. 



The fibrous tissue with the nuclei of connective tissue 

 corpuscles (corneal corpuscles). 



234. Examine (H.) a cornea silvered by the method 

 described in 232, c. The fibrous tissue is darkened by the 

 silver, and the connective tissue spaces are readily seen 

 forming an anastomosing system of channels ("lymph 

 canalicular system ") in which the corneal corpuscles are 

 placed, and through which the lymph from the marginal 

 capillaries can readily permeate. 



235. Examine (600 diam.) the nerves and corneal 

 corpuscles stained with gold by the method described in 

 330, b. Plexuses of nerve fibrils lie between the layers of 

 fibres, and may be exposed by stripping off the fibrous layers 

 from say the anterior surface of the cornea. Nerve fibres 



* The student is not permitted to do this. 

 K 



