430 



Messrs. S. G. Shattock and L. S. Dudgeon. [Mar. 18, 



wire ; the latter prevents the film from touching the grating, through 

 which the vapour freely passes to fix the film. The chamber is covered 

 with a piece of overlapping plate glass, after vaseline has been painted over 

 the edge. 



Before the slide is prepared, cover-glass films can be made in the usual 

 manner, and placed with the blood upwards upon the perforated zinc. The 

 glass lid being immediately replaced, the slide film is prepared and introduced 

 with the film downwards over the cover glasses, from off which it is kept by 

 means of the cross pieces of zinc wire on which it rests. 



After not less than 15 minutes (though the films may be left in the vapour 

 for 24 hours or longer, if convenient) the slide is removed and at once placed 

 in the vertical position in a glass of Scharlach for 24 or 48 hours. The 

 cover glasses are placed separately in hollowed glass blocks of the dye, 

 accurately covered to prevent evaporation. 



After a certain amount of experience we adopted, as a check, the practice of 

 treating one of the cover glasses after removal from the formol, and before its 



lx^2^^-4 — a 



Fig. 1. — A diagram showing the glass formol chamber and zinc grating used to fix the 

 blood films. The glass lid is not represented. Below the perforated zinc the space 

 is filled with cotton wool soaked in formol solution, 40 per cent. 



transference to the Scharlach, with absolute alcohol, followed by ether and 

 again by absolute alcohol ; the object of this was to remove any fat or fat-like 

 bodies from the cells of the film. At first, in making the cover-glass films, we 

 adopted the plan of adding salt solution to the blood on the cover, in order to 

 prevent any possibility of the film drying ; the film itself was made on each 

 cover glass separately by means of a platinum loop. This precaution was 

 found to be unnecessary, and we therefore discarded it. 



The use of alcoholic solution of Scharlach as a fat stain requires much care, 

 for the dye readily precipitates. The solution we employed was made by 

 saturating 75 per cent, absolute alcohol in the cold, and subsequent filtration 

 through paper first wetted with alcohol. In the case of a slide, the latter was 



