114 PRACTICAL HISTOLOGY. [ll. 



24. Dry Cover-Glass Preparation of Blood. Place a drop of frog's blood 

 on a cover-glass, and to it apply another cover-glass. Press the two glasses 

 together, and then slip them asunder. There will be a thin film of blood on 

 both glasses. Allow the films to dry. 



In a watch-glass place a dilute watery solution of methyl-green, and on this 

 float the cover-glasses, with the blood -surface next the staining reagent, as in 

 the method of staining bacteria. 



After ten minutes remove the cover-glass ; move it in water ; touch the 

 edge of it on blotting-paper to remove the surplus green fluid, and allow the 

 green stain on the glass to dry. After it is dry, add a drop of xylol balsam 

 and place the cover-glass on a slide. This forms a permanent preparation of 

 blood-corpuscles, whose nuclei are stained green. 



The same process may be practised with other aniline dyes, or eosin may be 

 combined with methyl-green, as the former stains the haemoglobin, and the 

 latter the nucleus. A very good stain is eosin-haematoxylin (p. 70). 



25. Double-Staining of Blood-Corpuscles (Methyl-green and Eosin}. Diffuse 

 a thin layer of frog's blood on a cover-glass, allow it to dry, and pour on 

 the dry residue a I per cent, watery solution of methyl-green. Leave it on 

 for ten minutes, and then wash off the surplus stain. Pour on a weak watery 

 solution of eosin, and after five minutes wash it off also by rinsing the slide 

 gently in water ; dry, and add xylol balsam ; cover. 



Observe that some of the corpuscles have the nucleus green and the sur- 

 rounding part coppery-red. Eosin is almost a specific reagent for detecting 

 haemoglobin. 



Numerous combinations of this kind may be made, such as magenta and 

 iodine-green, fuchsin and methylene-blue. 



26. A better plan is to place a drop of blood on a cover-glass, and to this 

 apply another cover-glass, press the glasses together, and then separate them 

 so that a thin film of blood adheres to each. Allow them to dry. After they 

 are dry, place them for two hours in a mixture of equal parts of absolute 

 alcohol and ether, which coagulates the proteids of the corpuscles. Float 

 the cover-glasses blood-surface downwards upon a saturated solution of methy- 

 lene-blue. After an hour or more, wash the cover-glasses in water, then in 

 absolute alcohol, and clear them up with clove-oil in which a little eosin is 

 dissolved. Remove the clove-oil by immersing the cover-glasses in xylol, and 

 mount in xylol balsam. A beautiful preparation is obtained. The nuclei are 

 blue, and the protoplasm of the colourless corpuscles of pale-rose colour. 



27. The advanced student should also study the effect of sulpho-cyanide 

 of potassium (5 per cent.), urea, ammonium chromate, pyrogallic acid, heat, 

 carbolic acid (i to 1000 of normal saline), and other agents on the coloured 

 corpuscles. Dilute alcohol reveals a nucleolus within the nucleus. This 

 preparation may be subsequently stained with magenta. 



28. Urea. A strong watery solution causes the corpuscles to assume 

 irregular forms and to send out processes, which may separate from the 

 corpuscle. Changes not unlike these are produced by neutral ammonium 

 chromate, very bizarre forms being thus produced. 



29. Bile, e*g., of mammal or frog, dissolves human red blood-corpuscles. 



30. Zinc Sulphate (.25-. 5 per cent.) causes the hremoglobin to separate 

 from the stroma. One may see it inside the corpuscle, or on the surface as 

 small buds. 



31. Pseudo-Membrane of the Corpuscles. Irrigate a preparation with 

 dilute alcohol. This decolorises the corpuscles. Then stain with magenta 

 or Spiller's purple. The nucleus and so-called membrane of the corpuscles are 

 thereby stained. 



32. Preservation of Blood-Corpuscles by Hayem's Fluid (p. 122). This is 

 an excellent method. The corpuscles retain their form, and can be subsequently 



