80 



210. Examining fresh. This consists in covering a drop 

 on a slide, and immediately sealing the cover-glass to prevent evapo- 

 ration, observing the following cautions: (1) The drop of blood 

 (from the finger or the lobe of the ear) should flow freely and not 

 be obtained by pressure. The drop should be a medium-sized one, 

 which will spread out in an even, thin layer under the cover. (2) 

 The drop should be received upon a cover or slide, covered, and 

 sealed at once with castor-oil. 



Examination of fresh blood may be used in clinical examination 

 for the detection of some abnormal conditions, and it is of value in 

 the rough diagnosis of many others. 



211. Stained preparation of blood, (a) Preparing the blood 

 film. This may be best done in one of two ways: (1) The edge 

 of a slide is first drawn through a drop of fresh blood and then moved 

 quickly across the surface of a clean cover-glass or slide, in this 

 way spreading the blood in a thin, even layer upon the glass. Success 

 depends upon getting the right amount of blood upon the edge of the 

 slide and the quick, even movement by which it is spread upon the 

 cover-glass or slide. Preparing the film on a slide is simpler and to be 

 preferred if a differential count of the leucocytes is to be made. A 

 second, possibly better, method is the following: 



(2) Have ready tw r o thin clear cover-glasses (or slides) and 

 obtain a drop of fresh blood. Take one of the covers in the forceps, 

 touch it to the drop of blood and place it upon the second cover- 

 glass eccentrically, with one edge projecting slightly. Slip the two 

 covers apart in the plane of their surfaces and dry them quickly by 

 waving them in the air or by passing them rapidly over the tip of 

 a flame. The lower cover-glass will have the better film. 



(b) Fixing the hemoglobin with (a) ether-alcohol or heat, or (b) 

 at the time of staining (methyl alcohol) ( 214). 



212. Fixing the film. When the blood films on the covers 

 are dry, place them in the fluid for J/2 to 1 or several hours. Let 

 them fix for a longer rather than a shorter time, as the quality of 

 the stain (with triacid mixture) will be improved. After they have 

 fixed a sufficient time remove and again dry them in the air. They 

 may now be stained, immediately or at convenience. 



213. Staining unfixed films. Eosin-Methylene Blue stains 

 (below). Fixed films may be stained w r ith hematoxylin and eosin as 

 well as with other stains. If the film is on the slide balsam and a 



