THE CHARACTERISTICS OF LIVING THINGS 11 



water that has evaporated. Keep the dry piece of plant for a later 

 experiment. 



(D) Get a small piece of raw meat, or a frog killed by chloroform. 

 Wipe dry with blotting- or filter-paper, and weigh. Dry and weigh 

 again, as in the case of the plant in the first experiment. What 

 proportion of the animal substance is water? Compare with the 

 plant. 



These experiments give us a general idea of the large 

 amount of water in animal and plant bodies. It would 

 require very careful experiments with very delicate apparatus 

 for weighing and special apparatus for drying in order to 

 determine the exact amount of water in plants and animals. 

 Careful investigations by chemists have shown that the body 

 of a higher animal (e.g., a dog) is nearly 70 per cent water. 

 This is believed to be true also of the human body. This 

 water is derived from that which we drink and also from foods. 

 Thus potatoes contain about 78 per cent water, milk 85 per 

 cent, tomatoes over 90 per cent, apples over 80 per cent, and 

 lean meat over 50 per cent. 



It is evident that water must play an important part in 

 the life of animals and plants, and in this connection it is 

 interesting to note the abundance of water and its wide 

 distribution over the earth. All good modern textbooks of 

 geography emphasize the close relation between the distribu- 

 tion of water and that of animal, plant, and human life. 



13. Gaseous substances, which are themselves lifeless, may 

 be obtained from the bodies of animals and plants. 



(D) Place the plant material left after drying in the above ex- 

 periment in the bowl of a clay tobacco-pipe, close the mouth of the 

 bowl with soft clay or plaster of Paris, support the pipe by a 

 wire or by a retort-stand, heat the bowl in the flame of a gas- or 

 alcohol-burner until it reddens and smoke (gases) begins to issue 

 from the pipestem, then light the smoke with a match. In an- 

 other pipe heat some splinters of wood or sawdust, and burn the 

 gas in the same way. A piece of dried meat heated in the same 

 way gives off gases, which may be burned. 



