168 THE PREPARATION OF BLOOD FOR 



precipitate does not after a while appear. This precipitate ahnost 

 always, if there have not been previous repeated and long-con- 

 tinued washings, at last spoils the preparations prepared according 

 to the original method." 



Zbc preparation of ffiloob for flDicroacopical 



lEyanunatlon** 



IN a recent number of the Medical Record^ Dr. Henry G. 

 Piffard alludes to a branch of blood examination, which, he 

 says, is exciting at the present time an increased and well- 

 merited interest. This is the preparation and examination of 

 blood spread in a thin layer and dried on cover glasses. 



Blood films are studied from several standpoints and with 

 several distinct objects in view. These are chiefly : To determine 

 the presence or absence of malarial plasmodia ; to ascertain the 

 presence or absence of the eosinophile, neutrophile, or basophile 

 granules of Ehrlich ; to observe changes and abnormal appear- 

 ances in the leucocytes and red corpuscles ; and to determine the 

 presence and kind, or absence, of micro-organisms. In all these 

 cases the manipulation is substantially the same, with the excep- 

 tion of the stains to be employed. It is this technique, he says, 

 which he desires to describe in the fullest detail, and with special 

 reference to the slide, the glass cover, the needle, the forceps, the 

 spreading of the film, the fixing and dehydration of the corpuscles, 

 the staining, the mounting, and the optical apparatus, and espe- 

 cially the condenser and objective. 



He states that the most satisfactory slides he has been able to 

 obtain are those furnished by Zeiss, at three and a half marks a 

 hundred. These are cut true to size (seventy-six millimetres by 

 twenty-six miUimetres), are of good glass, and are easily cleaned 

 for use with a drop or two of alcohol and a piece of Canton 

 flannel. Zeiss also supplies slides of plate glass at double the 

 price mentioned, but these it is almost impossible to clean with 

 either alcohol or acid. The slides chosen should be of medium 



* From the New York Medical Journal. 



