_The destructive action of the digestive enzymes leads us to believe that it is in inactive form that secretin is absorbed._ Like epinephrin, it cannot pass through the digestive tract. Bayliss and Starling state that it is destroyed by one hour’s tryptic digestion. Lalou[62] worked with the action on secretin of pepsin, dog’s gastric juice, pancreatic juice, succus entericus and erepsin, and found in each case a destructive effect, even almost after mixing; and after five minutes over 75 per cent. of the activity had disappeared. Matuso[36] introduced 30 c.c. of active secretin into the intestine, removed it five minutes later, and found that no activity remained. Other methods of administration have been tried. Subcutaneous injections are practically negative (Matuso,[36] Hallion[83]) and intrapleural injections are likewise negligible (Bayliss and Starling[55]). [83] Hallion: Presse méd. =20=:433, 1912. Starling[63] finds that continued intravenous injections of secretin in a healthy dog produces after a time severe symptoms of collapse, which, he believes, are due to change in the intestinal mucous membrane caused by the entry and non-neutralization of the strongly alkaline pancreatic juice. Intestinal digestion seems little affected in achylia gastrica (Stockton,[84] Ehrman and Lederer,[85] Bayliss and Starling[32]). This may be due to other secretin stimulants as fats, or to the action of the nervous mechanisms (Meltzer[86]). [84] Stockton: In Osier and McCrae’s Modern Medicine =3=:19, 1914. [85] Ehrman and Lederer: Deutsch. med. Wchnschr. =35=:879, 1909. [86] Meltzer, S. J.: The Factors of Safety in Animal Structure and Animal Economy, J. A. M. A., Feb. 23, 1907, p. 655. THE DESTRUCTION OF SECRETIN BY HUMAN GASTRIC JUICE We have carried out in detail experiments on the digestive effect of human gastric juice on secretin. Our results in every respect confirm the findings of Lalou,[62] who worked with commercial pepsin and dog’s gastric juice, but are even more striking because of the much superior quality of pure human gastric juice.