EESPIIi-\TION 107 



will retain most of any heat that may be given off (Fig. 

 69). If the temperature is recorded at the beginning of 

 the experiment, and again at the end, a rise of temper- 

 ature will be noted. In one experiment, set up with 

 germinating pea seeds (air dry weight 80 grams) in a 

 Dewar flask as above described, a rise of 19.3° was ob- 

 served within 96 hours. 



109. Respiration Versus Breathing,- — In the case of man 

 and other animals, the exchange of gases and evolution 

 of heat, demonstrated by the experiments described above, 

 are an index of respiration. The process of taking in 

 oxygen and giving off of carbon dioxide by animals is 

 called breathing. It is better to restrict the term breath- 

 ing to the mechanical exchange of gases between the lungs 

 of animals and the external air, and to confine the term 

 respiration to the oxidation processes of the living pro- 

 toplasm. It will thus be recognized that respiration is a 

 function of every living cell, and that the cells of our 

 fingers, for example, respire just as truly as do those of our 

 lungs and other organs. The lungs, by their mechanical 

 expansion and contraction, merely serve to bring the 

 oxygen of the external air into intimate contact with the 

 blood, which carries it to all respiring tissues of the body. 

 There is no process in plants comparable to this breath- 

 ing. In the case of some animals without lungs, certain 

 specialized organs (in fishes, the gills) are continually 

 bathed with external oxygen, which passes into the 

 blood hy diffusion. This more closely resembles the 

 process by which oxygen from the air passes into the 

 plant body. In other animals {e.g., earthworms) there 

 are no special organs for breathing, and the oxygen diffuses 

 through the moist body-walls. 



