96 THE LARVA OF THE BLOW-FLY. 



frothy and the air bubbles remain. Adjust the paraffin ribbon 

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

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

 100° 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 : 



Hasmatoxylin 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 nir. 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 sea Zeitsch. f wissensch. Mikr., iii., p. 150,* 1886, and Journ. 

 R. Micros. Soc. Lond., 2nd ser., vi., p. 1090, 1886. 



