96 THE LARVA OF THE BLOW- FLY. 



frothy and the air bubbles remain. Adjust the paraffin ribbon 

 on the shp and bring it everywhere into contact by means of a 

 clean wet camel's hair pencil. Place the slips in an oven at 

 lOo"" Fahr., and heat to the melting point of the paraffin. Allow 

 the slips to remain at this temperature at least two hours. 

 Prepare the following baths : 



1. Spirit of turpentine. 



2. Methylated spirit. 



3. Equal parts of methylated spirit and distilled water. 



4. Distilled water, 100 c.c, 10 /^ sol. hydrochloric acid, 



I c.c. 



5. Ehrlich's logwood.* 



1. The slips with the specimens attached are taken from the 

 oven and immersed in bath i whilst still hot. They should 

 remain from one to twenty-fours hours. Prolonged immersion 

 does no harm, but a trace of paraffin remaining prevents 

 staining. If the bath is not fresh it is as well to place them for 

 a few minutes in a second turpentine bath. 



2. The slips are removed from the turpentine and placed 

 face downwards in 2. The turpentine sinks to the bottom of 

 the spirit ; a second bath of spirit may be used with advantage. 

 They should remain at least ten minutes. Transfer to bath 3 

 for a few minutes, and to bath 4 for from five minutes to a 

 quarter of an hour. They should be moved about in bath 4 

 until the acidulated water lies smoothly on the slip. Pour a 



* I prepare Ehrlich's Logwood (Ha^matoxylin) stain as follows : 



Htematoxylin Crystals (the best), 2 grms. 



Absolute Alcohol, 100 c.c. 

 Dissolve and add — 



Distilled Water and Glycerine, 100 c.c. of each. 



Alum, as much as the mixture will dissolve. 



Finally add 5 c.c. of glacial acetic acid. 

 This stain should be kept at least a year in a corked bottle. If kept in a 

 stoppered bottle, the vessel should hold at least 600 c.c, and the stopper 

 should be removed occasionally to change the air. I believe the time 

 necessary to render the stain as good as possible may be much abbreviated by 

 shaking the vessel frequently, and I know its improvement is due to the 

 oxidisation of the alcohol. When recently prepared it is useless. For the 

 original formula see Zeitsch. f. wissensch. Mikr., iii., p. 150,' 1886, and Journ, 

 R. Micros. Soc. Lond., 2nd ser., vi., p. 1090, 18S6. 



