Intestinal blood flow in the dog measured by indicator fractionation without tissue samples

1. A modification of Sapirstein's indicator fractionation technique for measurement of intestinal blood flow has been studied and evaluated in the dog. 2. The concentration of 42K within the intestinal wall was measured simultaneously by a tissue assay procedure and by use of a miniature Geiger-Müller tube within the intestinal lumen. Both methods gave similar results under a wide variety of conditions. 3. Isotope measurement by the Geiger-Müller tube technique obviates the need for tissue samples to be taken and would permit repeat measurements of intestinal blood flow in the same animal.