EXERCISE 85 

 HOW DOES THE BLOOD CIRCULATE THROUGH THE CAPILLARIES? 



Materials. A compound microscope ; a frog ; a board such as a chalk-box cover, with a glass 

 slide fastened over a V-shaped notch in one end of the board ; chloroform or ether. 



Directions. Anaesthetize a frog by placing it in a small jar and adding a few cubic centimeters 

 of chloroform or ether. When the frog is completely under the influence of the chloroform or 

 ether, so that it will not withdraw its foot when extended, place one of its feet under the micro- 

 scope so that a part of the web is in focus, and hold it in position. Observe the flow of the blood, 

 the color of the blood, and any other points which you can see. What seems to be the rate of flow 

 of the blood in capillaries as compared with arteries and veins ? As the frog comes from under 

 the influence of the anaesthetic, is there any change in the rate of flow of the blood ? 



Additional problem. Mount a small fish or a tadpole so that the microscope shows the thin flesh of 

 the tail, and observe the circulation through the capillaries. This experiment may be used instead of 

 the v _above, no anaesthetic being necessary. 



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