“…This is probably not due to the presence of histamine, since when Ug was tested on the atropinized guinea-pig ileum it gave only a very small and slow contraction in a bath concentration of 10-5, whereas the gut responded well to histamine in a bath concentration of 4 x 10-9. However, the presence of this vasodilator substance would appear to be of mine technique (Rivers & Vanzant, 1937) and a 'dose' of urogastrone was defined as that quantity which reduced by 50 % the second response as compared with the first in dogs with vagotomized pouches of the entire stomach, secreting acid at the rate of 30-40 ml. of N/10-HCl/hr, i.e.…”