THE discovery by Bayliss and Starling(1) that the activity of the pancreas is normally excited by chemical means is now generally accepted, and even Pawlow's school, asis shown by a recent paper by Bylina2), regards the secretion of the pancreas as in the main dependent on a humoral mechanism. Bylina maintains that, in addition to the chemical mechanism, nervous influences are concerned in the excitation of the pancreas and indeed determine the chemical character of the juice secreted. The two first named authors showed that the pancreasexciting substance, secretin, is formed in the mucous membrane of the upper part of the small intestine under the influence of hydrochloric acid. Fleig(s) later pointed out that secretin might also be extracted from the mucous membrane of the small intestine by meanis of soap solutions. These two reagents are not however the only ones which may be employed for the extraction of secretin, and Fleig concluded that the secretins, obtained by various methods, really represented definite chemical individuals, for which he proposed special names, such as crinin, sapocrinin, ethylocrinin. I shall later have to discuss how far the criteria are justifiable which determined Fleig in coming to this conclusion.The discovery of Bayliss and Starling has enabled us to form a clear conception of the manner in which the secretion of pancreatic juice is normally evoked. The question arises whether Fleig's discovery, that soap solutions are a good ineans of extracting secretin from the mucous membrane, has any significance in the ordinary processes of digestion. Fleig showed that although an emulsion of olive oil and sodium carbonate was powerless to extract secretin from the intestinal mucous membrane, it acquired this power if treated with pancreatic juice and placed in the incubator for a short time, so as to saponify the
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