100 The Microscope. 



toto or not), such as a gland or ovary. Celloidine, however, is es- 

 pecially applicable to those specimens which are loose in texture and 

 the relation of whose parts may become changed by manipulation. 

 Since the introduction of this embedding mass the study of the eye 

 has been greatly facilitated. I have succeeded in making some good 

 sections of the whole eyeball as well as of the anterior equatorial 

 half. 



The eyes, as fresh as possible, should be hardened for several 

 weeks in a weak Muller's solution* taking care to change the fluid 

 frequently; or by putting the vessel in the warm chamber, the eyes 

 may be sufficiently hardened in a week or ten days, if the fluid be 

 changed daily. Then they should remain in running water for 24 

 hours and then hardened in alcohol by gradually increasing its 

 strength. The diffusion apparatus of Schultze is of great use here 

 in preventing the shrinking of the eye — a thing which only great 

 care will prevent. The celloidine should be used according to the 

 method described by Czermak j. A small incision is made tangenti- 

 ally in the sclera and also in the corneal edges and the eye is put 

 into equal parts of absolute alcohol and sulphui'ic ether, after 24 

 hours in ether alone, and the next day in a thin watery solution of 

 celloidine in ether. Great care is necessary here to prevent air bub- 

 bles from getting into the eye. To avoid this the eye should be deli- 

 cately seized with a small pair of forceps and shaken in the thin so- 

 lution with the two incisions upwards, so that the gravity of the 

 liquid will force out the air. 



After 24 hours the eye is put in thick celloidine and the vessel 

 is left partially uncovered, until the celloidine is hard enough to be 

 cut, and then the block containing the eye is cut out, softened a few 

 minutes in absolute alcohol, dipped once more in the celloidine solu- 

 tion and put on a cork, taking care that the preparation is in the 

 proper position. If many eyes are prepared in this manner at the 

 same time, it is well to burn numbers with an old needle on the 

 corks, noting the corresponding numbers in the working book, to 

 avoid confusion. The preparations on the cork should remain ex- 

 posed to the air until the celloidine is stiff and then allowed to float 

 in 84 per cent, alcohol until ready to be cut. Thin sections of whole 

 eyes may be made, or any desired part may be cut out with a sharp 

 razor and prepared without fear of disturbing the relations. 



The advantages of this method in studying the ciliaiy appara- 

 tus, are too apparent. The aniline colors must natui'ally be avoided, 



*Bichromate of potash, 1 to 2 parts; sulphate of sodum, 1 part; water 100 parts. 

 tArchiv fr. Ophthalinologie B-ind xxx. 



