[Illustration: Fig. 3.--Tracings (reduced one-half) showing practically complete destruction of secretin by the gastric juice. Dog under light ether anesthesia; cannula in the pancreatic duct; _a_, carotid blood pressure; _b_, record of flow of pancreatic juice in drops. Time, twenty-five minutes. Tracing A: intravenous injection of 10 c.c. secretin (prepared fresh from dog’s duodenal mucosa) at _x_. Tracing B: intravenous injection (at _x_) of 10 c.c. of the same secretin as in Tracing A, after being digested in normal human gastric juice at 37 C. for two hours.] We bought a quantity of Duodenin in the open market, and carried out on this product the same series of experiments as that used in the case of Secretogen. The results were similarly negative (Table 8). TABLE 8.--SUMMARY OF TYPICAL EXPERIMENTS SHOWING THE ABSENCE OF SECRETIN IN “DUODENIN” Dogs under ether anesthesia ================================================================= | | Secretion of Pancreatic Juice in Drops, | | Following Intravenous Injection Exp.| Number +--------+-------------------------------+---------- No. |Duodenin| Control| Duodenin in | Control | Tablets| 10 C.c.+---------+------+-------+------+ 10 C.c. | Used |Secretin|Distilled| 0.4% | 70% | 0.9% | Secretin | | | Water | HCl |Alcohol| NaCl | ----+--------+--------+---------+------+-------+------+---------- 1 | 3 | 29 | 0 | 0 | 0 | 1(?)| 28 1 | 6 | ... | .. | 1(?)| .. | .. | .. 2 | 18 | 16 | .. | 6 | .. | .. | 16 3 | 5 | 14 | .. | 0 | 0 | 0 | 8 3 | 25 | ... | .. | 1(?)| .. | .. | .. 4 | 100 | 110 | .. | 0 | .. | .. | 67 5 | 150 | 19 | .. | 0 | .. | 0 | 8 ----+--------+--------+---------+------+-------+------+---------- In regard to both Secretogen and Duodenin, we assume that the manufacturers have tried to put secretin in them, but have been unable because they have failed, in all likelihood, to check their methods by physiologic standardization. These firms do not give any details as to the procedure they employed in their manufacture of secretin. Desiccated secretin of extreme potency has been prepared by various physiologists,[91] 1 mg. (1/64 grain) of which is active when given intravenously. It is difficult to conceive that any of these methods were used in the preparation of Secretogen or Duodenin. [91] Stepp (Note 13). Dale and Laidlow: Jour. Physiol. =44=:11, 1912. Launoy and Ochslin: Comp. rend. Soc. de biol., =74=:338, 1913. CONCLUSIONS 1. Secretin is quickly destroyed by gastric juice and by trypsin. 2. Secretin is not absorbed in active form from the alimentary tract.