The blood of closed duodenal loop dogs is not toxic to normal dogs. The blood of dogs that have been fatally poisoned with duodenal loop fluid is likewise non-toxic to normal dogs.
The mucosa of closed or drained duodenal loops contains a toxic substance quite similar to the toxic material found in the lumen of the closed loops.
This toxic substance is absorbed from the mucosa itself and not from the lumen of the drained loops. The same is probably true of the closed loops which have an intact mucosa. It seems highly probable that the poison is formed by the mucosa and is in great part absorbed directly from it by the blood.
Normal intestinal mucosa contains no toxic substance nor can it neutralize in vitro the toxic substance produced in the closed loops.
There is no evidence that the toxic material when given intravenously is excreted by the intestine or held by the intestinal mucosa in any demonstrable form.
The toxic substance is not absorbed from the normal intestinal tract.
Destruction of the mucosa in a closed loop by means of sodium fluoride prevents the formation of the toxic substance. This fact furnishes the final proof that the mucosa is the essential factor in the elaboration of the poisonous material.