218 THE AMERICAN MONTHLY [Dec 



Fixing Blood for Microscopic Study. 



Complex technique in the preparation of microscopi- 

 cal preparations has done more to limit the use of the 

 microscope in the diagnosis of disease than any other 

 one thing. Take the ordinary directions for the prepa- 

 ration of a blood slide. First the most careful soaking 

 and scrubbing of cover glasses, then the application of 

 one of the glasses to the drop of blood, followed by a 

 second cover glass laid over the drop and the two pulled 

 slowly apart, with the result that in fully half of the 

 cases neither of the two cover glasses is spread in any 

 way suited to the purpose ; either no blood adheres or 

 the corpuscles are found overlying one another, or matted 

 to such an extent as to make them worthless. Finally^ 

 if a good spread is secured, fortunate is the ordinary 

 worker if he does not find, after following the advised 

 heat method for fixing, that he has not fixed the cor- 

 puscles, but simply distorted them. 



The following method of blood preparation requires 

 only ordinary skill and presents the advantage of almost 

 invariably giving first class specimens. A solution is 

 prepared which will mechanically separate the corpuscles 

 of blood mixed with it, and yet of such density and 

 composition as to permit them to retain their proper 

 shape and condition. There are several such solutions. 

 The formula suggested by Hayem is as follows : 



Chloride of sodium 1 part. 



Sulphate of soda 5 parts. 



Bichloride of mercury. 5 parts. 



Distilled water. 200 parts. 



Drop a few drops — about five — of this solution in a 

 small test tube or vial. Then after scrubbing the skin 

 with alcohol or ether, puncture with a triangular sur- 

 geon's needle. With a small wire loop or a pointed glass 

 rod quickly transfer a very small drop of blood from the 



