CHAPTl<ni XXX. 



liLOOD AND GLANDS. 



Bluod. 



717. Fixing and Preserving Methods — The school of Ehrlich 

 used to fix by heat. A film oi: blood was spread on a cover- 

 glass and allowed to dry in the air, and then fixed by 

 passing the cover a few times, three to ten or twenty, 

 through a flame, or by laying it face downwards on a hot 

 plate kept for several minutes or as much as two hours at a 

 temperature at which water not only boils but assumes the 

 spheroidal state (110° to 150° C). For details see Gulland, 

 Scottish lied. Journ., April, 1899, p. 312; Rubinstein, Zeit. 

 mss. Mih., xiv, 1898, p. 456 ; Zielina, ibid., p. 463. But I 

 believe they have now well-nigh abandoned this barbarous 

 practice. 



In ivet methods either the blood is mixed at once, on 

 being drawn, with some fixing and preserving medium, and 

 studied as a fluid mount, or films are prepared and put into 

 a fixing liquid before they hace had time to dry ; or after 

 drying in the air ivithout heat for a few seconds (at most 10 

 to 30). 



To make a film, place a very small drop of blood on a 

 perfectly clean slide. Bring down on to the slide the edge 

 of another slide held over it at a slope ; move this along till 

 it touches the edge of the drop and the blood runs along 

 the angle between the two slides. Then move the second 

 slide aioay from the drop, and the blood will follow it and bo 

 drawn out into a film without being crushed. Similarly with 

 two cover-glasses, to make a cover-glass film, which can be 

 floated face down on to fixing or staining liquids in a 

 watch-glass. 



