_Preparation._--All of the more dissociated acids liberate secretin from intestinal mucosa on boiling. Their action is dependent on the degree of dissociation,[39] carbonic and boric acids being inactive.[40] Secretin can also be prepared with strong soaps (from 10 to 30 per cent. sodium oleate), alcohol (70 per cent.,[41] 0.6 per cent. sodium chlorid[36]). The acid and soap in the duodenum produce secretion; there is no necessary correspondence between the action of a substance in the intestine and that obtained by injection after boiling mucosa with it. The sodium chlorid, bile, maltose and glucose produce some secretion by the latter method yet none by the former.[36] On the other hand, ether, chloral and oil of mustard excite secretion when in the intestine, but no secretin can be prepared from boiled mucosa by their action. The irritation of the lining cell has produced the necessary hydrolysis.[38] In well-controlled experiments, Wertheimer and LePage[42] found that after the introduction of acid, secretion is secreted into the lumen of the intestine. Matuso[36] confirmed their results, and found this a satisfactory method for the preparation of secretin. It is said that secretin can be obtained by merely boiling the mucosa with water, but the results are inconstant.[43] [39] Frouin and Lalou: Compt. rend. Soc. de biol., =71=:189, 1911. [40] Camus: Compt. rend. Soc. de biol., 1902, =54=:442, 1902. [41] Fleig: Jour. de physiol. et de path. gén. =6=:32, 50, 1904. [42] Wertheimer and LePage: Jour. de physiol. et de path. gén. =4=:1061, 1070, 1902. [43] Stepp: Jour. Physiol. =43=:441, 1912. _Action._--Secretin is an excitant not only of the pancreatic juice but also of the liver and the intestinal mucosa. The flow of bile is markedly accelerated (Henri and Portier,[44] Enriquez and Hallion[45]), likewise that of succus entericus (Delezenne and Frouin,[46] Bottazzi and Gabrielli[47]), and intestinal peristalsis is stimulated (Enriquez and Hallion,[48] Falloise[49]). Injections of secretin produce a marked vasodilatation, but the secretory effect is independent of the blood pressure changes. The pancreas is not readily fatigued by secretin. Bayliss and Starling[50] have obtained undiminished flow after eight hours of continuous injection. Our experience confirms this result. Also, equal doses of secretin give corresponding results at various intervals. Moreover, anesthesia does not affect the flow. Secretin is unrecoverable from the glands even after two hours of continuous injection.[51] The juice obtained by secretin has been subject to many studies.[52] It is of high alkalinity (about seventh normal), contains all the pancreatic ferments, and corresponds in all respects to the juice obtained in digestion from permanent pancreatic fistulas.[53] [44] Henri and Portier: Compt. rend. Soc. de biol. =54=:620, 1902. [45] Enriquez and Hallion: Presse méd. =1=:105, 1903. [46] Delezenne and Frouin: Compt. rend. Soc. de biol. =56=:319, 1904.