ORGANS OF THE ENERGIZING SYSTEM 77 



renewed. Therefore the functioning muscle must continually 

 receive both carbohydrate and oxygen from the blood that flows 

 through it. 



///. THE ORGANS OF THE ENERGIZING SYSTEM 



The action-systems of the animal body expend energy. Body, 

 limbs, etc., all move against friction. Further, the organs that 

 are concerned in the processes of organic functioning themselves 

 move : the heart and arteries expand and contract, the lungs dilate 

 and contract ; the walls of the alimentary canal exhibit peristaltic 

 contractions and so on. Finally, the tissues of the body may 

 generate heat. 



Thus organic behaviour is accompanied — and enabled — by the 

 dissipation of energy and so available energy must continually 

 enter the body — to become unavailable in the course of behaviour. 



The sources of this available energy are the nutritive materials 

 taken in and the oxygen that is used in respiration. Ultimately 

 all available energy used (or expended) in the organism, whether 

 animal or vegetable, comes from the oxidation of materials derived 

 from those other materials that are taken into the body. 



26. ON THE MATERIAL SOURCES OF ENERGY 

 These are oxygen and the food substances (or the raw materials 

 of the food substances). In the meantime we consider only the 

 food substances. 



26a. The Kinds of Materials taken into the Body. 



(i) By the typical plant organism. Water, taken in by the 

 root hairs from the medium in which the plant lives ; 



Carbon Dioxide, taken in by the stomata of the green tissues ; 



Compounds of Nitrogen, such as ammonia and its salts, 

 nitric and nitrous acids and their salts ; other inorganic N- 

 compounds ; these are dissolved in the intaken water ; 



Mineral Salts, alkaline chlorides, carbonates, phosphates, 

 etc., salts of iron, magnesium, manganese, etc. ; sulphates ; silica, 

 etc. : these also are contained in the intaken water. 



{ii) By the typical animal organism. The tissues of animals 

 and plants : proteins, fats and oils, carbohydrates (perhaps also 

 the cleavage-products of these substances) ; Water ; 



