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THE METABOLISM OF FATS AND CARBOHYDRATES 141 



whelms the liver, which is unable to arrest all of it. -That 

 which goes by raises the sugar content of the blood above 

 the level at which it begins to pass into the urine. 



If for any reason much of the glycogen in the liver or 

 the muscles is quickly resolved into sugar the blood must 

 be affected quite as though the added sugar had come from 

 the intestine. Glycosuria will ensue. Certain changes in 

 the circulation are known to cause such a flooding of the 

 system with sugar and the appearance of a part of it in the 

 urine. A most interesting instance of such glycosuria is 

 that following an experience of strong emotion. It 

 seems that one of the results of 'the disturbance in the 

 central nervous system is the conversion of a large amount 

 of glycogen into dextrose. With acute insight a physiolo- 

 gist has pointed out that this release of sugar is a helpful 

 reaction under the circumstances. The occasion of emo- 

 tion is usually an occasion for strenuous action, perhaps for 

 flight or for giving battle, and the muscles may be re- 

 inforced by the increased supply of their preferred fuel 

 brought to them. 



The regulating action of the liver and the muscles upon 

 the carbohydrate distribution may be paralleled, in part at 

 least, by an analogy. Let us compare the active tissues to 

 a mill turned by the waters of a stream. The water- 

 supply to the mill is to be compared with the sugar-supply 

 to the cells which derive their energy from it. A meal is to 

 the body as a storm is to the mill-stream it adds to the 

 volume of the power-producing element. The dam by the 

 mill is like the kidney in its relation to the accumulated 

 store; if the water rises above the crest of the dam it flows 

 over and passes on down the stream without having con- 

 tributed its energy to the turning of the machinery; if 

 the sugar rises above a certain level it begins to escape, 

 with its potency for work lost to the organism. More- 

 over, the capacity of the liver and the muscles to hold back 

 carbohydrate suggests the function of a broad mill-pond. 

 The larger the pond above the dam the more successfully 

 the irregularities due to alternating rain and drought will 



