266 



The Microscope. 





be in excess, lest the water cause some change ; it should be 

 sufficient however, to allow the corpuscles to flow readily under 

 the cover. The amount of moisture to be imparted by the 

 breath is soon learned after a trial or two. If desired, a layer 

 of oil may be placed around the cover glass and thus prevent 

 the drying of the specimen. 



Examined with a magnifying power of about 450 diameters 

 one never fails in a specimen prepared as above to see most 

 beautiful and perfect representations of the rouleaux, where a 

 greater or less number of red corpuscles adhere together by 

 their flat sides. 



Another satisfactory method of obtaining a thin layer of 

 blood is to draw the edge of a smooth glass slide over the fresh 

 blood and then drawing this edge of the slide across the flat sur- 

 face of another slide. The thin cover is at once applied and the 

 specimen examined. 



FIG. 1.— A. Human red blood-corpuscles in rouleaux, a, white corpuscles, x 400. 

 B. Human red blood-corpuscles, a, seen on edge, b, white corpuscle, x 1000. 



THE RED CORPUSCLE. 



1. The Rouleaux. — Prepared according to the first method, 

 as already stated the first thing noticed is the arrangement of 

 the red corpuscles into rows. It is rather difficult to explain 

 why the corpuscles so arrange themselves. One author says 

 that if a number of circular corks be taken and cut compara- 

 tively thin, and made concave to represent the red corpuscle in 

 shape ; and if a pin be placed in the edge of these corks and a 

 weight, ;is a bullet, attached to the free end of the pin ; and if 

 a number of these corks thus prepared be put into a tub partly 

 filled with water and the water agitated, of course the corks 



