844 PHYSIOLOGY 



immediately by an excessive secretion of urine and the appearance of sugar 

 in this fluid. The glycosuria may last from twenty-four to thirty hours. 

 If at the end of this time the animal be killed, the liver is found to be free 

 from glycogen. A sample of blood taken during the height of glycosuria may 

 contain from 3 to 4 parts of sugar per 1000. In order that the experiment 

 may succeed it is important that the animal be previously well fed. If the 

 puncture or ' piqure ' be carried out on an animal that has been starved or 

 whose liver has been freed by any means from glycogen, no glycosuria 

 is produced. It is evident that the effect of the puncture has been to cause 

 a rapid conversion of the glycogen previously stored up in the liver into 

 glucose. The glucose so formed escapes into .the blood, raising the sugar 

 content of this fluid above the normal, and the excess is immediately excreted 

 by the kidneys together with an increased amount of water. A similar 

 temporary hyperglycaemia and glycosuria may be brought about by fright, 

 struggling or the administration of anaesthetics; but the effect is absent, 

 if both splanchnic nerves have been previously divided above the supra- 

 renals. It has been shown (Elliott, Cannon) that all these conditions are 

 associated with an increased discharge of adrenaline from the medulla of 

 the suprarenals into the circulation. Since the injection of adrenaline itself 

 causes a condition of diabetes similar in all its limitations and aspects to 

 ' puncture diabetes/ it is now generally believed that the two conditions are 

 identical, and that the diabetic puncture acts through the splanchnic nerves 

 on the suprarenals, setting free adrenaline, which passing to the liver causes 

 a rapid ' mobilisation ' of the stored-up glycogen, and a consequent hyper- 

 glycsemia and glycosuria, lasting as long as the glycogen store holds out. 



(3) PHLORIDZIN DIABETES. Phloridzin is a glucoside extracted from 

 the root cortex of the apple-tree. It may be decomposed into a sugar 

 and phloretin. When phloridzin or phloretin is administered by the mouth 

 or subcutaneously, it gives rise to glycosuria, unaccompanied, at first at any 

 rate, by any other symptom. The urine may contain from 5 to 15 per cent, 

 of glucose. The glycosuria induced in this way differs from the forms 

 already described in the fact that it is not due to hyperglycsemia. Analysis 

 of the blood shows that the sugar is slightly diminished rather than increased. 

 The excretion of glucose seems to be due to a specific effect of the drug 

 upon the kidneys. If cannulse be placed in the two ureters so as to collect 

 the urine from each kidney separately, and a small dose of phloridzin be 

 then injected by a hypodermic syringe into the left renal artery, the urine 

 flowing from the left ureter will in two minutes be found to contain sugar, 

 while the urine from the right kidney will not contain any sugar for another 

 five or ten minutes. The effect therefore is rapidly to drain off sugar from 

 the blood. In order to maintain the sugar content of the blood at its normal 

 height, the liver must manufacture fresh sugar to take the place of 

 that lost by the kidneys. In the first instance the liver will utilise its 

 stored-up glycogen for this purpose. If a dose of phloridzin be given to 

 each of two animals and one animal killed as soon as the excretion of sugar 

 is coming to an end, the liver will be found free from glycogen. If now a 



