. Biology . ecret. Some few points, however, are known. Theimmediate source of energy for such movements is the com-bustion or oxidation, through the action of enzymes, of partsof the cellular protoplasm, and if no food were taken in, theorganism would soon die from loss of its vital parts. This loss,however, is constantly made good by capture and digestion offood, functions involving the primary and fundamental activi-ties of all animals and plants, these functions being the central 48 ORGANISMS OF ONE CELL factors in the development of the multifold structures in theliving world. Amoeba prot
. Biology . ecret. Some few points, however, are known. Theimmediate source of energy for such movements is the com-bustion or oxidation, through the action of enzymes, of partsof the cellular protoplasm, and if no food were taken in, theorganism would soon die from loss of its vital parts. This loss,however, is constantly made good by capture and digestion offood, functions involving the primary and fundamental activi-ties of all animals and plants, these functions being the central 48 ORGANISMS OF ONE CELL factors in the development of the multifold structures in theliving world. Amoeba proteus captures food and draws it into the body-protoplasm through the agency of the pseudopodia, or rather,the protoplasm of the organism streams into pseudopodiaaround the prey, thus engulfing it (Fig. 19). Some water isengulfed with the food particle and this forms the chief portionof the liquid of the gastric vacuole. This water usually isalkaline in reaction when taken into the body; soon, however, \:k (S). Fig. 19.—Amoeba dividing (A), ingesting food, and encysted (D). p,Retracted pseudopodium; dt, diatom taken in as food; other letters as in Fig. 18.(From Sedgwick and Wilson after Leidy and Howes.) it changes in reaction from alkaline to acid, the change beingbrought about by the secretion of an acid digestive fluid fromthe surrounding endoplasm. Through the action of thisacid (supposed to be HCl), the food particle, if hving, is firstkilled and then disintegrated.^ Later the reaction of the con-tents of the vacuole again changes from acid back to alkaline,and in this medium the further processes of digestion are accom-plished. The end result of this series of chemical actions onthe food is the formation of proteoses from the protein sub- 1 No enzyme analogous to pepsin and acting in this acid medium is known tooccur in Amoeba proteus. AMOEBA PROTEUS 49 stances which, as soluble materials, are then taken into thebody protoplasm of the organism; the food particles are said
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