THE METABOLISM OF THE CARBOHYDRATES 713 



are isolated from the animal; for if they should, a much more searching 

 investigation of the essential cause of their inability would be possible 

 than is the case when they are functioning along with the other organs 

 and tissues. The earlier experiments of Lepine and his pupils, which seemed 

 to show that diabetic blood did not possess the glycolytic power of 

 normal blood ; and those of Cohnheim, from which it was concluded that 

 mixtures of the expressed juices of muscle and pancreas, although ordinarily 

 destroying glucose, failed to do so when they were taken from a diabetic 

 animal, are now known to be erroneous. 



The failure to show a depression of glycolytic power by these methods 

 prompted Knowlton and Starling 24 to investigate the question whether 

 any difference is evident in the rate with which glucose disappears from 

 a mixture of blood and saline solution used to perfuse a heart outside 

 the body, according to whether the heart was from a normal or a dia- 

 betic dog. In the first series of observations which these workers made, 

 it was thought that the normal heart used glucose at the rate of about 

 4 mg. per gram of heart substance per hour; whereas that of a dia- 

 betic (depancreatized) animal used less than 1 mg. If such striking 

 differences in the rate of sugar consumption could make themselves 

 manifest for so relatively small a mass of muscular tissue as that of the 

 heart, it is permissible to assume that a much more striking difference 

 could be demonstrated when the perfusion fluid is made to traverse all 

 or practically all of the skeletal muscles, as well as the heart. For this 

 purpose an eviscerated animal may be employed that is, one in which 

 the abdominal viscera are removed after ligation of the celiac axis and 

 mesenteric arteries, and the liver is eliminated by mass ligation of its 

 lobes. Using such preparations, R. G. Pearce and Macleod 29 found that 

 the rate at which glucose disappears from the blood, although very 

 irregular, is in no way different in completely diabetic as compared 

 with normal dogs. They were thus unable to cojifirm any of Knowlton 

 and Starling's earlier conclusions. As has already been stated Patterson 

 and Starling subsequently pointed out that a serious error was involved 

 in the earlier perfusion experiments, partly on account of a remarkable 

 but irregular disappearance of glucose from the lungs, and partly be- 

 cause the diabetic heart may contain a considerable excess of glycogen, 

 from which its demands for sugar may be met without calling on that 

 of the perfusion fluid. 



More recent work by Starling and Evans, in which the respiratory ex- 

 change of the heart in heart lung preparations from diabetic (pancreatic) 

 dogs was determined, has revealed a low R.Q. (0.71) although the oxygen 

 consumption was normal. These workers consider that their results indi- 

 cate "a depression or abolition of the power of the diabetic tissue to utilize 



