538 METABOLISM, NUTRITION AND DIETETICS 



tracts of pancreas and extracts of muscles, distinct glycolysis, due 

 to a ferment action, could be produced. He suggested that the 

 glycolytic ferment is activated by another substance, as trypsinogen 

 is activated by enterokinase (p. 366). This announcement aroused 

 great interest, since it is known that the pancreas is intimately 

 concerned in the metabolism of sugar. That sugar disappears 

 under the conditions of Cohnheim's experiments has been confirmed 

 by a number of observers. But his interpretation of his results has 

 not been generally accepted. According to Levene and Meyer, 

 the dextrose, far from. being burnt, seems to be condensed to a poly- 

 saccharide, and can be recovered by hydrolysing this compound 

 when the mixture is acted on by dilute acid. The action of the 

 pancreas-muscle mixture is, therefore, not a true glycolysis. In- 

 deed, of all the tissues investigated by Levene, leucocytes alone can 

 be credited with a real glycolytic action. Excision of the pancreas 

 in dogs causes permanent glycosuria (pancreatic diabetes) (v. Mering 

 and Minkowski), which is prevented if a portion of the pancreas be 

 left (p. 622). Diabetes in man is known to be frequently associated 

 with pancreatic lesions. Although much still remains obscure, the 

 study of this pathological form of glycosuria and of the experimental 

 glycosurias has thrown light upon the normal metabolism of carbo- 

 hydrates and upon those regulative mechanisms whose breakdown 

 is responsible for the excretion of sugar. It will be best to discuss 

 the experimental glycosurias first, and to begin with the form which 

 probably is better understood than any other, the so-called punc- 

 ture glycosuria. 



Puncture Glycosuria- Sugar-Regulating MechanismW An arti- 

 ficial and temporary glycosuria, in which the sugar in the urine un- 

 doubtedly arises from the hepatic glycogen, can be caused by punc- 

 turing the medulla oblongata in a rabbitV for example, at a level 

 between the origins of the auditory nerves and the vagi. It is stated 

 that a puncture of the thalamencephalon, or 'tween-brain (p. 822), 

 produces the same effect. If the animal has been previously fed with 

 -a diet rich in carbo-hydrates that is, if it has been put under con- 

 ditions in which the liver contains much glycogen the quantity of 

 sugar excreted by the kidneys will be large. The immediate cause 

 of the glycosuria is an increase in the sugar content of the blood 

 (hyperglycaemia), an increase which is most pronounced in the blood 

 of the hepatic vein. If, on the other hand, the animal has been 

 starved before the operation, so that the liver is free, or almost free, 

 from glycogen, the puncture will cause little or no sugar to appear 

 in the urine, and the proportion of sugar in the blood will remain 

 normal. That nervous influences are in some way involved in the 

 mobilization of the glycogen reserve of the liver is shown by the 

 absence of glycosuria if the splanchnic nerves, or the spinal cord 

 above the third or fourth dorsal vertebra, be cut before the puncture 



