294 



BLOOD AND BLOOD EXAMINATION 



these are carefully cleansed in ether and alcohol so that fat, fiber and all parti- 

 cles of dust are removed. [Water is sufficient for cleansing cover-glasses pro- 

 vi^ded they are properly polished with silk or tissue paper afterwards. — Ed.] 

 On a cover-glass of this kind a small drop of blood which has exuded from a 

 prick of the finger is collected; this glass is dropped, blood side downward, 

 upon a second glass, with the result that the blood soon spreads out spon- 

 taneously in a thin film between the two very flexible glasses to about three- 

 quarters of their extent, as if in a capillary space. After a complete distribu- 

 tion of the drop of blood, the glasses are removed from one another [by 

 sliding off the upper of the two covers without any lifting or tilting, but 

 strictly in the plane of their surfaces. — Ed.], and the blood is seen distributed 



upon each in a uniform 

 layer. If the drop taken was 

 small enough, the blood cells 

 are found in an even layer 

 side by side without over- 

 lapping each other. In view 

 of the fact that the red 

 blood-corpuscles are dam- 

 • aged with extraordinary ease. 

 Fig. 18. 11, especially by moisture, this 



maneuver should not be at- 

 tempted with the unaided hand ; for the moisture of the tip of the fingers is ■ 

 capable of changing the outlines of the red blood-corpuscles and of extracting 

 their hemoglobin. For this reason, in the preparation of these specimens two 

 forceps should be used in the manner 

 depicted in Pig. 18. [For any one whose 

 fingers are not habitually and obviously 

 damp the use of forceps is unnecessary. 

 —Ed.] 



When the blood films have dried, 

 which usually happens within twenty to 

 thirty seconds, it is necessary before 

 subjecting them to the stain to fix the 

 blood in a suitable manner. For practi- 

 cal purposes it is sufficient usually if the 

 specimens are placed for five minutes in 

 a solution of 1.0 formol in 100 parts of 

 absolute alcohol. After this method of 

 fixation almost all the stains which need 

 practically be considered may be em- 

 ployed. If we intend, however, to pre- 

 pare especially beautiful specimens, or 

 to make investigations for scientific pur- 

 poses, then Ehrlich's old method— fixation by heat alone— had better be 

 utilized. Most serviceable for this purpose is a small copper kettle (Fig. 

 IJ) mside of which a small quantity of toluol is brought to the boiling point. 



Fig. 19. 



