THE FROG 169 



ties into the left auricle? What is its condition when it 

 leaves the ventricle? Does this circulation of impure blood 

 affect the temperature of the body? How? What is a 

 cold blooded animal? 



(7) Slightly chloroform a frog and tie the toes apart 

 on a notched board so that the web may be placed on the 

 stage of the microscope. Under the microscope notice the 

 blood vessels and the blood moving in them. Do you see 

 the arteries and capillaries? Can you distinguish between 

 arteries and veins? Do you see corpuscles in the blood? 

 Draw what you see much enlarged. Increase the amount 

 of chloroform until life is extinct and open the body as be- 

 fore. The heart will probably be still pulsating. Watch 

 the movements. Circulation of blood in capillaries may be 

 plainly seen also in the tail of the tadpole. 



(8) Remove a drop of blood and mount it on a slide. 

 Notice the pale red circular disklike bodies, the corpuscles, 

 and the fluid, plasma, engulfing them. Do you find also 

 irregular white masses? These are white blood corpuscles 

 and are really living cells, similar in some respects to amoeba, 

 which live in the blood and have an aimless uncertain mo- 

 ton. Draw red and white corpuscles. 



(9) The circulation of the kidneys has been described. 

 Remove from the body, the alimentary canal, the liver and 

 lungs, and expose the kidneys and the reproductive organs. 

 Trace the urinary tube, the ureter, from the kidneys down to 

 the cloaca. Draw the urinary system. What is the office 

 of the urinary system ? 



IV. Reproductive System. — Look close to the dorsal 

 side for reproductive bodies; in the male these are testes, 

 rounded, somewhat yellowish bodies ; and folded or lobed 



