XV 



THE METABOLIC MACHINERY OF ANIMALS 



Preview. Section A . Intake devices and how they function • Foods and 

 their uses ; energy producers ; non-energy producers ; vitamins ■ The acti- 

 vators — enzymes • Digestion in lower animals • Digestion in higher ani- 

 mals ; methods of increasing digestive surfaces ; parts of the digestive 

 system : The oral cavitj^, the pharynx and esophagus, the stomach, the 

 small intestine, the large intestine ; the digestive glands and their enzymes : 

 The salivary glands, the gastric glands, the intestinal glands, the pancreas, 

 the liver, the secretions of the small intestine ; absorption and the fate of 

 absorbed foods • Section B. The how and why of circulation • Why a 

 transportation system • Unspecialized transportation systems ■ Open cir- 

 culatory systems • Closed circulatory systems : Among invertebrates ; among 

 vertebrates • The blood • The lymph • The conduits — arteries, veins, and 

 capillaries • The heart • The aortic arches • The course of blood in the 

 body ; functions of the blood • Section C. Respiratory devices • Respira- 

 tion ; the protein, hemoglobin ; external respiration : Respiratory papillae, 

 respiratory pouches or trees, lung-books, the body surface, gills, tracheae, 

 lungs, internal respiration ; respiratory system in man • Section D. Ex- 

 cretory mechanisms • Excretion ; types of excretory devices : Contractile 

 vacuoles, intracellular excretion, other excretory devices ; excretory devices 

 of vertebrates — kidneys ; the mammalian excretory system : The liver, 

 other devices for waste elimination, the kidneys • Suggested readings. 



PREVIEW 



The body has often been compared to a machine. This analogy 

 probably holds best when speaking of the preparation of food for 

 combustion, the actual release of energy, and the resulting work 

 done, as well as the disposal of the end products. It is this group of 

 processes with which we will here be concerned. All animals are in 

 constant competition with one another for food. If herbivorous they 

 may be competing amongst themselves directly for plant food ; if 

 carnivorous, the competition is more indirect. Food, whether it is 

 animal or plant by nature, is being continuously sought to maintain 

 that complex series of processes called by some authors the "flame 

 of life." An earlier unit describes how plants take raw materials, 

 such as water, carbon dioxide, and nitrogenous compounds, and build 

 them up into foods which may then be used or stored. The plant 



271 



