VII. 



THE BLOOD. 

 A. The Structure of Blood. 



Materials. A drop of human blood. To obtain a drop of blood, 

 tie a string or wind a handkerchief tightly around the finger and 

 wait a few minutes until the blood has collected in. the finger. 

 Then with a clean needle make a prick near the nail. Let a drop 

 of blood fall on a glass slide. Spread out the blood very thin by 

 placing a second glass slide over the first and rubbing it about. 

 Then remove the second glass slide, place a cover-glass over the 

 blood and the slide is ready for examination. A prepared slide of 

 the blood of a frog. 



Apparatus. Glass slides. Cover-glasses. Compound microscope. 



I. THE HUMAN BLOOD. 



Examine a drop of human blood under the microscope. 

 Notice : 



a. The red corpuscles. What is theirshape and arrangement? 



b. The white corpuscles. What is their relative size and 

 shape ? What is their relative number ? 



c. The delicate threads of fibrin. 



d. Sketch. . 



II. THE FROG'S BLOOD. 



Study with the microscope a slide of the blood of the frog 

 prepared by double staining to show the nuclei of the red 

 corpuscles. 



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