Il] BLOOD CORPUSCLES OF FROG 17 



there is usually some lymph under it, and this will dilute the blood, 

 besides adding small finely granular basophil and other cells to the 

 drop. If pure blood from the heart is required the pericardial fluid 

 should be washed away with salt solution before the heart is cut, and 

 the salt solution sopped up with blotting-paper ; the pericardial fluid 

 contains a considerable number of small finely granular basophil 

 cells. 



The dry film should be examined (h.p.) before staining ; if the 

 outlines of the red corpuscles are indistinct, another film should be 

 prepared. 



13. Staining a film with eosin. See that 3 small 

 wide-mouthed bottles are ready, the first containing a 

 saturated solution of eosin in 75 p.c. alcohol, the other 

 two containing 75 p.c. alcohol. Have ready also a pad 

 of half-a-dozen pieces of smooth filter or blotting-paper, 

 without fluff. Take up the cover-slip by one corner 

 with forceps, or fasten one corner into the end of a 

 wooden match, (this corner should not be dipped in the 

 fluids) ; hold it for a minute in the eosin solution, let 

 the excess of fluid drain off (5 seconds), hold the 

 cover- slip for 5 seconds in the first bottle of alcohol 

 and for 5 seconds in the second bottle of alcohol. 

 Then place without delay between the pads of filter- 

 paper and lightly press, shift the cover-slip at once to 

 a fresh place, and again lightly press. Wave the cover- 

 slip in the air to dry it. When dry place a small drop 

 of Canada balsam on the centre of the cover-slip, and 

 lower this slowly on a glass slide. 



Note the deep red stain of the granules of the 

 coarsely granular leucocytes (the oxyphil granules). 

 The red corpuscles should be separate, of normal shape, 

 with distinct outlines and rather deeply stained with 

 eosin. 



L, 2 



