284 THE AMERICAN MONTHLY [Sept 



These considerations led me to try and work out a 

 method which would allow of the staining and keeping 

 of nucleated blood in bulk ready for distribution to the 

 class and so fixed that there should be but little distor- 

 tion of the corpuscles. 



The red blood cell is a delicate structure and some care 

 in its manipulation is required. 



If the. steps of the method are strictly followed one 

 may be confident of a successful issue. 



Chloroform the animal selected ; a large frog is proba- 

 bly the most convenient ; open the thorax, puncture the 

 aorta and allow the blood to flow directly into a small 

 glass jar, with ground glass stopper, containing a one 

 per cent aqueous solution of osmic acid. The solution 

 should be largely in excess of the amount of blood, at 

 least fifty times as great. The vessel is now closed and 

 set aside for several hours in which time the blood cells 

 will have become thoroughly fixed and hardened and have 

 settled in a thin layer at the bottom. 



Decant the supernatant fluid and add distilled water, 

 gently agitating the vessel until the blood is thoroughly 

 mixed with the water. Again decant after sedimentation 

 has taken place or filter rapidly through very thin filter 

 paper and wash off the filtrate in a small quantity of dis- 

 tilled water. 



Next add Bohmer's haematoxylin diluted one-half with 

 distilled water. Use no more of this mixture than enough 

 to promote quick and thorough admixture with the water 

 containing the blood. After a few moments staining fil- 

 ter as before, wash the filtrate from the paper by agitat- 

 ing in a large dish of distilled water and set the vessel 

 aside for an hour or more in order that the nuclei of the 

 cells may be well differentiated. 



Dehydration is now accomplished by running the blood 

 through various strengths of alcohol beginning with 70 

 per cent and ending with absolute, filtration or decan- 



