Digestive system bacterial action

The introduction of amino acids directly into the blood stream, unlike the injection of whole protein as a plasma transfusion, presents no unusual physiological problem inasmuch as normal protein nutrition involves the entrance of these same builtfing stones of protein into the blood stream. There is, however, a difference between an injection into the systemic veins, whereby all the amino acids as such quickly reach all the tissue at one time, and the gradual, and perhaps inconstant absorption of variable amounts of various amino acids, after being subjected to bacterial action, into the portal vein and thence to the liver alone during the digestion of food protein. In order to evaluate the metabolism of intravenously injected amino acids, this difference must be scrutinized. 

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