102 Animal Microloyy 



eosin method (reagents 49, 40, Appendix B) or with the Ehrlich-Biondi 

 stain (38, Appendix B). The blood fixed in Hermann's fluid may be 

 stained by the saffranin-gentian violet method (66, Appendix B). 



3. Amoeboid Movements in Leucocytes may readily be observed in blood 

 (preferably amphibian) which has been mounted on a slide in very 

 slightly warmed normal saline. Place a hair under the cover-glass and 

 seal the edges of the latter with vaselin or melted paraffin. For continu- 

 ous study of the white corpuscles of warm-blooded animals a warm stage 

 of some kind is necessary, to keep the temperature of the blood near the 

 temperature of the body. 



4. Feeding Leucocytes. Rub up sufficient India ink in a few drops of 

 normal saline to make a grayish fluid. With fine scissors make an inci- 

 sion into one of the dorsal lymph sacs of a frog (parallel to and close 

 beside the urostyle). Introduce a capillary pipette into the wound and 

 obtain a small drop of lymph. Mix it on a slide with a drop or two of 

 the prepared ink. After placing a hair across the field put on a cover- 

 glass and seal the edges with vaselin or melted paraffin. Under a high 

 power of the microscope the cells may be seen engulfing the colored 

 particles. 



5. Wright's Stain for Blood. To prepare the stain make a 0.5 per cent, 

 solution of sodium bicarbonate in distilled water and add to it 1 per cent, 

 of methylen blue (Griibler). Subject the mixture to steam in an ordi- 

 nary steam sterilizer (e. g., Arnold; not a pressure sterilizer or a water- 

 bath) for one hour. When the mixture is cool, without filtering, pour it 

 into a large dish. Prepare a 1 per cent, aqueous solution of Griibler's 

 yellowish eosin (soluble in water) and, with constant stirring, add it to 

 the methylen-blue solution until the blue color is replaced by purple, and 

 a yellowish scum with metallic luster forms on the surface of the mixture, 

 while a finely granular black precipitate appears in suspension. The 

 proportions required will be about 500 parts of the eosin to 100 parts of 

 the methylen blue solution. Collect the precipitate on a filter, dry it 

 thoroughly, make a 5 per cent, solution in pure methylic alcohol. To 

 prevent the alcohol from evaporating keep the bottle containing the solu- 

 tion tightly stoppered. Should precipitation occur, filter the stain and 

 add a small quantity of methyl alcohol. 



Mallory and Wright in their Pathological Technique, p. 374, give 

 the following summary of the method for staining blood films; 



"1. Make films of the blood, spread thinly, and allow them to dry in 

 the air. 



"2. Cover the preparation with the staining fluid for one minute. 



" 3. Add to the staining fluid on the preparation sufficient water, drop 

 by drop, until a delicate, iridescent, metallic scum forms on the surface. 

 Allow this mixture to remain on the preparation for two or three minutes. 



