386 THE .CORNEA, BY ALEXANDER ROLLETT. 



lead, and the salts of copper, and subsequent treatment with 

 sulphuretted hydrogen, sulphide of ammonium, cyanide of 

 potassium, and the like* These methods likewise all tend 

 to prove the existence of the above-described protoplasmatic 

 plexus ; the nature of the action, however, in each case is only 

 capable of being understood when we consider at the same time 

 the material or matrix in which the cells occur, a subject 

 upon which we shall have occasion to enter into more detail 

 hereafter. 



From the foregoing observations it will be seen that the 

 chloride of gold deserves the highest praise as a means of 

 bringing the corneal corpuscles into view ; nevertheless there 

 is still another method I would recommend, which consists in 

 immersing the cornea in aqueous humour, and placing it in a 

 cell,f where it can absorb the vapour of iodine. 



The cornea assumes a brown tint in the iodine cell, and the 

 epithelium can then be easily brushed away. On removing it, 

 but replacing it if requisite in the cell, the cell-plexus of the 

 cornea appears with a distinctness that is little if at all inferior 

 to the gold preparations. The migrating cells are also brought 

 very clearly into view, in consequence of their becoming stained 

 of a beautiful brown colour. The absorption of the iodine 

 vapour takes place with great rapidity, and its operation can 

 be followed with the microscope. The method is absolutely 

 certain for the fixation of transitory conditions of the cornea, 

 and cannot therefore be sufficiently commended. Every one 

 who is accustomed to "work with chloride of gold knows 

 that, however excellent the results when the preparation is a 

 successful one, something is defective in the method, since it 

 not unfrequently occurs that even when the greatest care has 

 been taken partial or complete failure happens, and that for 

 certain investigations this constitutes a very great disadvan- 

 tage to it. Not only is the simple representation of the cell- 



Beziehung zum Bindegewebe, (The lymphatics and their relations to con- 

 nective tissue,) p. 4, et seq. Berlin, 1862. 



* Leber, Zur Kenntniss der Impragnationsmethoden der Hornhaut und 

 ahnlichen Gewebe, Archivfiir Ophthalmologie, Band xiv., pp. 300 316. 



t Described by me in the Untersuchungen aus dem Institute fur 

 Physiologic und Histologie in Graz., pp. 15 and 18. Leipzig, 1870. 



