10 BACTEEIOLOGY OF THE EYE 



When the object is not very large, a preliminary staining with lithium carmine 

 or alum carmine can be carried out in the block, and a whole eye can be so stained 

 after cutting off a calotte. The stained object is then embedded in paraffin or 

 celloidin. Paraffin sections must be fixed down to the slide (dilute alcohol usually 

 is sufficient to effect this), and can be stained after the paraffin has been dissolved 

 out and the section carried into alcohol. Celloidin sections must be pressed down 

 on the slide. Under no circumstances should sections be placed loose in these 

 solutions, as they will certainly curl up. 



The previously mentioned anilin-gentian-violet solution can be used for staining, 

 and the treatment with the iodine (Lugo!) solution is the same. After drying up 

 the iodine solution the decolorization must be done as follows : Plunge the slide 

 into anilin xylol (2 : 1), or rapidly pour that fluid over it until no more blue clouds 



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* -i - ' .,.. ... - .*. *""I" >5 : a ** *-"*' 



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FIG. 2. PNEUMOCOCCI IN HUMAN CORNEA, PROGRESSIVE BORDER OF ULCER. 

 GRAM-WEIGERT STAIN, PNEUMOCOCCI BLUE. 



can be washed out and the former colour returns to the section ; dry, wash rapidly 

 with fresh xylol till all the anilin oil is removed (otherwise the staining is only 

 temporary), and mount in balsam. 



It must be emphasized that staining in sections does not always succeed so 

 readily as in films. The process must sometimes be varied. For many sections it 

 is better to mix equal parts of anilin water with a saturated solution of gentian 

 violet in alcohol, and to place the section for several seconds in this mixture. 



The demonstration of Gram-negative microbes in sections is much 

 more difficult, and sometimes quite impossible. The following 

 methods are comparatively certain. On account of the frequency of 

 Gram-negative organisms in ophthalmology I will give several of 



