348 TEGUMENTAEY ORGANS. 



ground-substance shows the well-known blue of reduced gold. 

 The cells are, however, visible, being recognisable by their 

 granular appearance and pale yellow tint. 



RBNAUT (Comptes Rend., 1880, l er sem., p. 137) gives the 

 following process for corneal corpuscles : Cornea of frog: 

 formic acid, 20 per cent., ten minutes ; gold chloride, 1 per 

 cent., twenty-four hours; formic acid, 33*3 per cent., twenty- 

 four hours. 



659. Cornea, other Methods (ROLLETT, Strieker's Handb., p. 

 1102). Rollett strongly recommends the following plan : A 

 fresh cornea is placed (in humor aqueus) in a moist chamber, 

 and exposed to the action of iodine vapour. As soon as it has 

 become brown the epithelium may easily be peeled off. If the 

 reaction is not complete the cornea may be put back into the 

 iodine chamber. When sufficient iodine has been absorbed 

 the preparation may be examined, and it will be found that 

 the network of corneal cells is brought out with an evidence 

 hardly inferior to that of gold preparations. The method 

 never fails, which is not the case with the gold method. It 

 is admirable as a fixing method. 



For dissociation of the fibres Rollett recommends macera- 

 tion in a solution of permanganate of potash or a mixture of 

 this solution with alum. As soon as the tissue has become 

 brown it is shaken in a test-tube with water, and breaks up 

 into fibres and bundles of fibres. 



TAETUFERI (Anat. An*., v, 1890, p. 524; Zeit.f. wiss. Mik., 

 vii, 3, 1890, p. 365) has the following method for demonstrat- 

 ing corneal cells and the ramifications of their processes : A 

 cornea is placed for three or more days in a solution of 15 

 grammes of hyposulphite of soda to 100 c.c. of distilled water, 

 kept at a temperature of about 26, then removed for two 

 days into water containing very finely powdered chloride of 

 silver (if left longer the corneal cells will not be stained, but 

 innumerable elastic fibres will be demonstrated). The pre- 

 parations are said to be permanent. 



For cell-division in the membrane of Descemet, see SCHOTT- 

 LANDER'S methods, ante, 643. 



660. Crystalline (Hardening of) (LowE, Arch.f. mik. Anat., 

 1878, p. 557). A fresh bulb is placed in a vessel containing 



