81 



cover-glass are unnecessary if it is to be examined with the oil immer- 

 sion objective. 



214. Eosin-Methylene Blue. The most of the formulas are 

 made on the principle of neutral stains, eosinates of methylene blue 

 dissolved in methyl alcohol, the staining solution being diluted with 

 water during the staining ( 85, b). As polychrome methylene blue 

 is generally used, the range of selectivity is increased by the presence 

 of methylene azure. 



(a) Nochts-Hastings Stain. ( 130). Stain blood smears 1 

 minute with the undiluted stain, then dilute with distilled water 

 until a metallic film begins to appear and the diluted stain appears 

 reddish at the edge. Stain 5 minutes more, rinse quickly with dis- 

 tilled water, absorb excess with absorbent paper, dry in the air; 

 when dry mount in balsam. 



(b) Wright's stain ( 129) is of similar composition and the 

 staining process is carried out in the same manner. Stain blood 

 smears 1 minute with the undiluted stain ; dilute drop by drop with an 

 equal volume of water and stain for 3 minutes; rinse, dry, etc., as 

 above. 



(c) Jenner's stain ( 128) is a simpler stain, and easier to use. 

 The simple (i. e., not polychrome) methylene blue is used, and 

 the differentiation of the stain is secured in the washing out. Stain 

 blood films 3 minutes or more, rinse a short time with distilled water 

 (until the best portions of the film are pink) . Absorb excess of water 

 with absorbent paper and dry in the air. When dry, mount in 

 balsam. 



215. It is sometimes advantageous, as for class work and with 

 non-mammalian blood, to handle blood in bulk. The following 

 method has been used with good results. Fix for 1 to 6 hours by 

 having the blood drop into a vial of 1% osmic acid. The blood-cells 

 are allowed to settle and the supernatant fluid removed with a pipette. 

 By this method the blood is passed through, successively, 2 or 3 

 changes of distilled water, 50%, 67% alcohols, paracarmine, 67%, 

 82%, 95% and absolute alcohols, xylene, to thin xylene balsam ( 161) 

 in which the blood is stored. By gently agitating, the corpuscles are 

 evenly distributed and a drop of the balsam mounted contains 

 numerous blood cells. This is an excellent method for preparing 

 isolated epithelial and muscle cells for class use. Such material may 

 be kept for years and is always ready to use. 



