Methods for Preparing and Staining Blood 



Prenarations. 



The steps for obtaining blood preparations are as fol- 

 lows : — Arrange on a piece of filter paper a number of 

 carefully cleaned cover glasses; these must be very thin, 

 extra number one. Ehrlich washes the cover glasses first 

 in strong sulphuric acid, rinses in water, and places them 

 for a few moments in "glacial acetic acid ; the}- are then 

 washed in flowing water until all the acid is removed, 

 transferred to 95% alcohol, from which they are taken and 

 wiped. Unless the cover glasses are thin and clean, no 

 good preparation can be made. The finger is pricked with 

 a steel pen, one of the prongs of which has been broken 

 off. From the flowing blood a xevy small drop is caught 

 on the cover glass, near its edge, and the glass quickly 

 placed, blood side downward, on another cover glass, care 

 being taken to cover this second cover glass only about 

 half. The blood will be seen to spread out between the 

 two covers. Quickly draw one cover glass from the other; 

 a thin layer of blood will in this wa^- be spread o^both 

 slips. Ten to twenty preparations are to be made in this 

 way, and placed, blood side up, on the filter paper before 

 you, and allowed to dry. Before staining, the preparations 

 need to be fixed. This is done by one of the following two 

 methods. You may harden the preparations in — 



Ether ...... 3 parts. 



Absolut^ilcohol .... 1 part. 



In thifsolution they remain for 1 to 24 hours, are then 

 set aside for a few moments until the ether and alcohol 

 evaporates, when they are ready for staining. 



