RESPIRATION 1 07 
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 adn 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 by 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. 
