THE BLOOD 39 



of the red corpuscles into rows. They are easily recognized by their 

 larger size and by their silvery appearance, due to the light shining 

 through them. 



To examine White Corpuscles. Obtain from the butcher a small 

 piece of the neck sweetbread of a calf. Press it between the fingers 

 to squeeze out a whitish, semi-liquid substance. Dilute with physiolog- 

 ical salt solution on a glass slide and examine with a compound micro- 

 scope. Numerous white corpuscles of different kinds and sizes will be 

 found. Make sketches. 



To prepare Models of Red Corpuscles. Several models of red 

 corpuscles should be prepared for the use of the class. Clay and putty 

 may be pressed into the form of red corpuscles and allowed to harden, 

 and small models may be cut out of blackboard crayon. Excellent 

 models can be molded from plaster of Paris as follows : Coat the 

 inside of the lid of a baking powder can with oil or vaseline and fill it 

 even full of a thick mixture of plaster of Paris and water. After the 

 plaster has set, remove it from the lid and with a pocket-knife round off 

 the edges and hollow out the sides until the general form of the cor- 

 puscle is obtained. The models may be colored red if it is desired to 

 match the color as well as the form of the corpuscle. 



