ABSTRACT
The number of red blood cells in the islets of Langerhans has been considered as a useful index of the insulin synthesis, i. e. of the functional state of the B cells of the islets. It was found, however, that in starved rats which had only received water orally, the red blood cell content within the islets increased both absolutely as well as relatively to that in the exocrine parenchyma at the same time as the decrease in the B cell function as estimated by caryometry. There was a marked correlation, both in the control group and in the starved rats, between the red blood cell concentration in the exocrine and endocrine parts of the pancreas. The extent to which a rise in the functional activity of the A cells might have contributed to the increased content of red blood cells in the islets during starvation is discussed.