and Laboratory Methods. -^07 



A Review of the Methods of Staining Blood. 



The vast amount of work on the blood in recent years, consequent to its 

 growing importance in diagnosis and to the activity in the investigation of the 

 malarial parasites, has produced such an extensive literature and has developed 

 such a complexity of methods for preparing and staining this aggregation of 

 cells for microscopical study that a collection of this literature and a review of 

 these methods seem worth the while. For the earlier literature on this subject 

 I am indebted to Miiller, Die Methoden der Blutuntersuchungen, Zusammen- 

 fassendes Referat (Centralbl. f. allge. Pathol, u. path. Anat., 1892, Oct. 31, 

 Nov. 18), and to Mannaberg, Die Malaria Parasiten, Wien, 1893. The intro- 

 duction of dry blood films in the study of the blood by Ehrlich in 1878-79 sup- 

 plied a simple and quick method of preparing the blood cells for staining which 

 has superseded all others. And nearly all of the subsequent literature on stain- 

 ing the blood has been concerned with these dry films. For these reasons this 

 review will be occupied chiefly with the methods of preparing, fixing and stain- 

 ing dry blood films. 



I. MAKING THE PREPARATIONS. 



Blood from the human subject is best obtained by puncturing the thoroughly 

 cleansed lobe of the ear or the tip of the finger with a three-cornered surgeon's 

 needle, from most other mammals by puncturing one of the small veins of the 

 ear, and from the lower vertebrates and some of the small mammals by chloro- 

 forming the animal and taking the blood from the internal organs. In every 

 case one should endeavor to obtain small, freshly exuded drops rather than an 

 extensive flow of blood. 



The dry blood film consists essentially of a small drop of fresh, uncoagulated 

 blood spread upon a cover-glass, one layer of corpuscles deep, which dries 

 almost instantly, fixing the corpuscles flat upon the glass before they have time 

 to shrivel or become distorted. The main points in the somewhat difficult tech- 

 nique are cover-glasses absolutely clean and free from greasiness, the use of 

 only a small drop of freshly exuded blood and rapidity of manipulation. Two 

 general methods for securing this thin distribution of the blood upon the cover- 

 glass are in use, some preferring one and some the other method. 



1-. The Method of Ehrlich. — This is the method more generally recommended. 

 It consists in touching the surface of a cover-glass to a small drop of fresh blood 

 and dropping it blood downward upon a second cover-glass. The blood spreads 

 by capillarity in a thin layer between the two cover-glasses, which are immedi- 

 ately slid from off one another without lifting apart. If the cover-glasses were 

 clean and free from grease and the proper amount of blood was taken a thin film 

 of blood is left on both cover-glasses, which are placed blood upward to dry. 

 The sliding apart of the cover-glasses is facilitated by dropping the first upon 

 the second so that their corners do not coincide. The drying of the blood films 

 can be hastened by waving the cover-glass to and fro in the air. 



A Modification of the Method of Ehrlich. — Several pairs of cover-glasses placed 



