THE ABSORPTION AND USE OF FOODS 497 



the disease should throw much light on the mechanism of the 

 consumption of fuel by them. The presence of sugar in the urine 

 is only one of the symptoms of diabetes mellitus. A symptom of 

 equal importance is the muscular weakness, and particularly the 

 lack of endurance, which results from the failure of the tissues to 

 make use of their fuel supply to advantage. 



A very interesting feature of this condition is that it can be in- 

 duced experimentally in a quite unexpected way, namely, by in- 

 juring or removing the pancreas. Complete destruction of this 

 organ is followed by an apparent total loss of the power of the 

 tissues to use sugar; there is excessive muscular weakness, and 

 death occurs in a few days after the operation. The effects of 

 partial destruction are less severe; in fact no symptoms appear 

 unless fully three-fourths of the gland are destroyed. The func- 

 tion of the gland in connection with the prevention of diabetes is 

 wholly independent of its function as a digestive gland. The 

 duct of the pancreas may be tied without the production of dia- 

 betes, or the gland may be transplanted from its usual location 

 to some other, quite abnormal one, where, if it lives and estab- 

 lishes connections with the circulation, it suffices to prevent 

 diabetes perfectly. 



The interpretation of this function of the pancreas is that it is 

 a hormone action. The gland produces the hormone, and this, 

 when carried by the blood to the tissues, in some way enables 

 them to use sugar; perhaps by activating some tissue enzym or 

 enzyms upon which the oxidation of sugar depends. It is not 

 thought that the ordinary secreting cells of the pancreas produce 

 the hormone, but that certain peculiar groups of cells embedded 

 in the gland, the Islands of Langerhans, have this function. Al- 

 though not all physiologists agree in assigning the production of 

 the hormone to the Islands of Langerhans, the general trend of 

 opinion seems to be that that is their function. 



Diabetes mellitus in man not only shows symptoms agreeing 

 precisely with those seen in animals with injuries to the pancreas, 

 but many cases show on autopsy very well marked lesions of the 

 Islands of Langerhans. We may thus conclude with fair cer- 

 tainty that the disease is one affecting these Islands, and that its 

 symptoms are the result of more or less complete failure of the 

 hormone formed by them. 



