910 NUTRITION AND HEAT REGULATION. 



excreted, somewhat as the phenol, indol, etc., are conjugated! 

 with sulphuric acid and excreted. The relationship of glycuronie 

 acid to sugar is indicated by the following formulas : 



CH^OH COOH 



(CHOH), (CHOH)^ 



COH COH 



Dextrose. Glycuronie acid. 



Whether this product is used solely for protection against toxie 

 substances, or constitutes one member of a normal series of metabo- 

 lisms of the sugar molecule has not been determined. 



Regulation of the Sugar-supply of the Body. — The regulation 

 of the sugar-supply of the body is a matter of the greatest im- 

 portance. On the one hand we have the process of the conversion 

 of sugar to glycogen, glycogenesis, as it has been called, and the 

 subsequent gradual reconversion of this glycogen to sugar (glyco- 

 genolysis), according to the needs of the body. On the other hand, 

 we have the processes of consumption of sugar in the tissues for 

 energy purposes, a process designated often as glycolysis, the 

 nature of which is discussed in the preceding paragraph. It i& 

 evident that these various processes must be adapted one to an- 

 other, for we know that if for any reason the percentage of sugar 

 in the blood rises but slightly above the normal, a condition desig- 

 nated as hyperglycemia, there occurs an escape of sugar in the 

 urine (glycosuria). Regulations undoubtedly exist for the control 

 and adaptation of these several processes, and at one point or 

 another these regulations may break down with a resulting dis- 

 turbance in sugar consumption that manifests itself usually by 

 the development of a condition of glycosuria. In the first place- 

 it may be recalled that glycosuria, so-called alimentary glycosuria,, 

 may result from eating an excess of carbohydrate. In this case 

 apparently sugar absorbed from the alimentary tract is sup- 

 plied to the liver more rapidly than the latter organ can synthe- 

 size it to glycogen. The breakdown in regulation is in the proc- 

 ess of glycogenesis. Stimulation of sensory nerves or lesions of 

 the central nervous system may also produce glycosuria. One of 

 the most interesting experiments in this connection is the piqiire 

 or "sugar puncture," first noted by Claude Bernard (1855). A 

 slight puncture of the medulla, made between the levels of ori- 

 gin of the vagus and auditory nerves, results in the appearance of 

 sugar in the urine. The phenomenon has been much investigated, 

 and opinions have differed as to the mechanism of the reaction. 

 According to the older view, the increased sugar production is due- 

 to the fact that the puncture stimulates nerve-fibers that act upon 

 the liver cells and cause an augmentation of the process of glyco- 

 genolysis. The nerve-fibers in question pass down the cord and,. 



