

LESSON II. 

 BLOOD. 



(a) Fresh Human Blood. 



Obtain a drop of blood by pricking a carefully cleaned finger 

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

 quickly mount the drop on a slide, and examine with the high 

 power. 



Observe that most of the red cells are arranged in 

 rouleaux, and between these now and then a white cor- 

 puscle is seen. If your drop was small, some of the red 

 corpuscles found in the peripheral part of the preparation 

 will appear crenated. 



(b) Fresh Human Blood with Normal Salt. 



Obtain a very small drop of blood as above directed, mix it on 

 the slide with a drop of normal salt solution, and cover. 



The smaller number of corpuscles will allow of a more 

 careful study of their size and shape. Observe that the 

 red appear as biconcave circular discs, and are a little 

 smaller than the majority of the white. Some of the red 

 will soon be crenated. Make a drawing of a number of 

 the red cells as seen on u the flat," and a few seen on the 

 edge (profile). 



(c) Human Blood Stained in Haematoxylin and 



Eosin. 



A small drop of blood was spread between two clean square 

 cover glasses (No. 1, % in.); the cover glasses were then quickly 

 drawn apart, and the thin film of blood allowed to dry. The cover 

 glass with the blood was then placed for 1 to 24 hours in a solution 

 composed of 3 parts of ether and 1 of absolute alcohol which fixes the 

 blood, it was next stained for 15 to 20 minutes in Boehmer's hsem- 

 atoxylin, and for 5 minutes in a \% solution of eosin, washed in 

 flowing water and dried between filter paper. Mount on a small 

 drop of balsam. 



