148 MICROMETRY AND BLOOD PREPARATIONS. 



the flame until the urea melts. This shows that a temperature be- 

 tween 130 and 135 C. has been reached. 



One of the handiest methods is to drop a few drops of 95% alcohol 

 on the slide or cover glass. Allow this to flow over the entire surface; 

 then get rid of the excess of alcohol by touching the edge to a piece o. 

 filter paper for a second or two. Then light the remaining alcohol 

 film from the flame and allow the burning alcohol to burn itself out. 

 A chemical fixation which gives good fixation for haematoxylin and 

 tri-acid stains (not equal to heat) is a modification of Zenker's fluid 

 (Whitney). To Muller's fluid, which is potassium bichromate 2 gms., 

 sodium sulphate i gm. and water 100 c.c., add 5 gms. of bichloride of 

 mercury and 5 c.c. of nitric acid (C. P.). Fixation is obtained in 5 

 seconds. 



Staining Blood-films. As separate staining with eosin and 

 methylene blue rarely gives good preparations and as the modifications 

 of the Romanowsky stain recommended are easy to make and employ, 

 and give much greater information, the separate method of staining is 

 not recommended. The most satisfactory single stain is thionin. 



Rees' Thionin Solution. Take of thionin 1.5 gms., alcohol 10 c.c., 

 aqueous solution of carbolic acid (5%) 100 c.c. Keep this as a stock 

 solution. It should be at least two weeks old before using. For use, 

 filter off 5 c.c. and make up to 20 c.c. with water. 



1. Fix films (a) by heat, (b) by alcohol and ether, or (c) preferably 

 by i% formalin in 95% alcohol for i minute. 



2. Stain for from 10 to 20 minutes. Wash and mount. Malarial 

 parasites are stained purplish; nuclei of leukocytes, blue; red cells, 

 faint greenish-blue. 



Ehrlich's Tri-acid or Triple Stain. There are required : 



1. Sat. aq. sol. orange G. (Dissolve 3 grams in 50 c.c. water.) 



2. Sat. aq. sol. acid fuchsin. (Dissolve 10 grams in 50 c.c. water.) 



3. Sat. aq. sol. methyl green. (Dissolve 10 grams in 50 c.c. 

 water.) 



These three solutions may be kept as stock solutions. They keep 

 well in the dark. To make the stain: Add 9 c.c. of No. 2 (acid 

 fuchsin) to 18 c.c. of No. i (orange G.). After they are mixed 

 thoroughly, add 20 c.c. of No. 3 (methyl green). Then, after the first 



