ANIMAL ACTIVITIES. 
186 
produced by a pushing out of the walls of the tube 
itself (Fig. 143). 
Excretion. Carbon dioxide and water are taken by 
the blood-corpuscles to the breathing organs and to the 
skin, where they are thrown out of the body. Urea and 
SMALL 
INTESTINE 
STOMACH 
LARGE 
INTESTINE 
12 INCH 
DUODENUM 
Fig. 142.—Digestive Organs of Man. 
water are taken from the blood by the kidneys and 
passed along to the urinary bladder and thence out ol 
the body. 
Reproduction and Metamorphosis. The female 
frog deposits her eggs in the water in spring in large 
jelly-like masses. As soon as hatched the young tad- 
