Lesson II. 

 BLOOD. 



(a) Fresh Human Blood. 



01)tuiu ;i (Irup of blood by pricking a carefully cleaned finger 

 witli a steel pen, one of the prongs of which has been broken oft'; 

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

 power. 



Observe that most of tlie 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 

 cor[)UScles found in the peripheral part of the preparation 

 will appear crenated. 



(b) Fresh Human Blood w^ith 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 stud}' 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 " the flat," and a few seen on the 

 edge (profile). 



(c) Human Blood Stained in Heematoxylin and 



Eosin. 



A small di'op of blood was spread between two clean square 

 cover glasses (No. 1, ^4 in.); tlie cover glasses were then quickly 

 drawn apart, and tlie 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 minntes in Boehmer's htem- 

 atoxylin, and for .5 minutes in a 1% solution of eosin, washed in 

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

 drop of balsam. 



