THE HISTORY OF AN INSECT'S STOMACH 



By R. E. Snodorass 

 Bureau of Entomology and Plant Quarantine, United States Department of 



Agriculture 



There is nothing that more strongly attests the kinship of all 

 things living than the common function of feeding. The Brother- 

 hood of the Animal Kingdom is established on the stomach. The 

 history of the stomach is little less than coextensive with the history 

 of animal evolution. 



The fundamental nature of the act called " feeding ", or, in other 

 words, the physiological significance of the verb " to feed ", is the 

 supplying of material to living matter that can replace the material 

 constantly being discarded as a result of the vital activity in living 

 matter known as metdboJism. The live substance of all plants and 

 animals is contained in minute structural units called " cells." Physi- 

 ological feeding, therefore, is a matter of attending to the nutri- 

 tional needs of the body cells, and, on the part of an animal, is not 

 merely the act of eating or filling a cavity popularly known as the 

 " stomach " with a mass of potential food material. In the case of 

 complex animals this procedure is only the beginning of a long series 

 of physical and chemical processes that must take place before the 

 cells are served. The function of filling the stomach, which in prac- 

 tice we so exalt as a social function while we attempt to hide its 

 crudity with conventional methods of technique, is physiologically 

 comparable with the delivery of raw foodstuffs to the kitchen. 



The so-called " living " substance of the body is proto'plasm^ but it 

 is doubtful if any matter itself is " alive " in the sense that we vaguely 

 attribute to the word. The state of being alive, in its simplest phase, 

 is the unique property of protoplasm by which it liberates energy 

 and keeps on liberating energy, and includes also the power of proto- 

 plasm to grow by adding to its own substance. The energy of life 

 is stored in complex molecules, which either are a part of protoplasm 

 or are contained in protoplasm, and these molecules must be broken 

 down in order to set free the stored energy; but immediately a new 

 reserve of energy must be made available in new molecules built up 

 in protoplasm to replace those destroyed. Hence, metabolism, which 



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