MOISTURE 65 



dependent on the stored energy of the plant and animal kingdom. 

 From their method of oxidation it is necessary to recognize two 

 groups of bacteria: (1) Those which completely oxidize their 

 food, the carbon and hydrogen occurring in the final products as 

 carbon dioxid and water; (2) those which only partly decompose 

 their food, thus leaving much of the energy still within the food. 

 Now the actual food requirements of the two classes of organism for 

 the accomplishment of the same end, in so far as energy is con- 

 cerned, is materially different. For instance, the complete oxida- 

 tion of glucose to carbon dioxid and water as brought about by some 

 yeasts according to the equation CeH^Oe + 6O 2 = 6CO2 + 6H 2 O + 

 674 cal. ; whereas, when only partly oxidized to alcohol it would be 

 C 6 H 12 6 = 2C 2 H 5 OH + 2C0 2 + 22 cal. 



The energy obtained in the first case is over thirty times that 

 obtained in the second, and the quantity of food decomposed would 

 be relatively greater in the latter than in the former. It has been 

 estimated that the lactic acid bacteria decompose their own weight 

 of sugar in one hour. 



Although all organisms require the elements listed at the begin- 

 ning of this chapter, yet the nature of the organic compound required 

 varies greatly with different species. 



Moisture. Moisture may be considered the most important 

 factor of life. "It is little short of astounding that living matter 

 with all its wonderful properties of growth, movement, memory, 

 intelligence, devotion, suffering and happiness should be composed 

 to the extent of from 70 to 90 per cent, of nothing more complex or 

 mysterious than water. Such a fact as this is most perplexing, espe- 

 cially when all experiments show that this water is playing a pro- 

 foundly important part in the generation of the vital phenomena. 

 Any interference with the amount normally present makes a change 

 at once in the activities of the cell. In fact we might say that 

 'all living matter lives in water,' as Claude Bernard put it. For 

 not only is this obviously true in the lower and simpler forms of 

 animals and plants, which are little more than naked masses of 

 protoplasm living in water, but it is no less true of the higher 

 forms, since in all of them an internal medium, or environment, of 

 a liquid nature, the lymph, the blood or sap, is found which is the 

 immediate environment of the cells. Water is the largest and one 

 of the most important constituents of living matter, and if organisms 

 are carefully examined the most various devices are found to assure 

 the regulation of the water content of the cells of the body. The 

 younger, the more vigorous, the more alive, the more actively 

 growing, the more impressible cells are, the more watery are they." 



Water enters very largely into the composition of the bacterial 

 cell, since they consist of from 70 to 95 per cent, water; moreover, 

 it enters into nearly every change which they bring about. When 

 5 



