and Laboratory Methods. 1515 



shallow basin, and washed with ordinary tap water until no trace of the yellow 

 color of chromic acid remains. The water is next poured off, and the slips are 

 covered with rectified spirit. After this they are washed in absolute alcohol, 

 and handled with clean forceps. 



If two cover-glasses are used for the mount, they are accurately superposed 

 and firmly pressed together. An edging of vaseline, if for temporary pur- 

 poses, or cement if for permanent purposes, is laid over all the edges, 

 except one, and a very small portion of that edge which is opposite the 

 uncemented one. A drop of blood is touched with the free edge of the paired 

 cover-glasses, whereupon the blood enters between the glasses in an exceedingly 

 thin film, the corpuscles being spread out with beautiful uniformity, and having 

 suffered a minimum amount of change from exposure to air and none at all from 

 handling or pressure. When the blood film has entered, the free edges may be 

 completely closed, and the examination made. 



If slide and cover-glass are used the latter is placed on the slide in such a 

 position that one of its edges exactly coincides with that of the slide. It is then 

 firfnly pressed, and sealed with vaseline or cement, as when two cover-glasses 

 are used, and the subsequent course pursued as with covers. By this method 

 a number of mounts may be made and stored in a suitable air-tight bottle, and 

 thus be always ready for use. Fresh blood keeps well under these circum- 

 stances. No special skill is required for the making of first-class blood film. 



This method has been carefully tested, and it was found necessary to put 

 the smallest possible amount of cement between the covers before edging them 

 outside, otherwise the cement had a tendency to run in. — Knowledge^ 24: 183. 



c. w. J. 



Methods of Staining the Gonococcus. 

 Schiitz method : 



1. Stain for five to ten minutes in sat. sol. methylen blue in 5 per cent. 



carbolic acid water. 



2. Differentiate for three seconds in : 



Acetic acid, ... 1 part. 



Water, dist., .... 4 parts. 



3. Wash in distilled water. 



4. Counterstain in dilute solution of safranin. 



Neisser's method : 



1. Stain in cone. ale. sol. of eosin, slightly warmed, for two or three 



minutes. 



2. Remove excess of stain with filter paper, and counterstain with cone. 



ale. sol. methylen blue for fifteen to thirty seconds. 



Chenzinski's methylen blue and eosin : 



Methylen blue, sat. aq. sol., ... 2 parts. 



Eosin, 0.5 per cent, in 70 per cent, alcohol, . 1 part. 

 Distilled water or glycerin, ... 2 parts. 



With this solution cocci stain blue, pus cells pink. 



