. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. DIGESTION IN THE SMALL INTESTINE. 415 as already mentioned, by the fact that the gland itself contains but little ready-formed proteolytic ferment, but a substance termed zymogen, which, from exposure to the atmosphere, or under the action of dilute acid, is readily converted into ferment. Heidenhain has determined that the amount of zymogen in the pan- creas coincides in amount with the extent of the granular zone; there- fore, in pancreatic s
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. DIGESTION IN THE SMALL INTESTINE. 415 as already mentioned, by the fact that the gland itself contains but little ready-formed proteolytic ferment, but a substance termed zymogen, which, from exposure to the atmosphere, or under the action of dilute acid, is readily converted into ferment. Heidenhain has determined that the amount of zymogen in the pan- creas coincides in amount with the extent of the granular zone; there- fore, in pancreatic secretion, as in the case of saliva, the act of secretion possesses two phases: the first, the preliminary stage of separation from the blood; the second, the stage of manufacturing of those constituents' into the specific ferments of the secretion. As regards the action of the nervous system on the secretion of. Fig. 163.—Pancreas of the Dog in the Second Stage of Digestion. (.Heidenhain.) pancreatic juice but little is known. Both section and stimulation of the central end of the pneumogastrics temporarily arrest the flow of pancreatic juice ; vomiting also has the same effect, the result being probably due to the stimulation of this nerve. Stimulation of the gland itself by an induction current, as well as stimulation of the medulla oblongata, seems to produce an increase in the secretion, but section of the spinal cord does not raise it. When all the nerves going to the pancreas are divided, a continuous flow of pancreatic juice commences, and under these circumstances the fluid formed has but slight digestive power, and its amount is not influenced by the taking in of food. Injec- tions of ether into the stomach produce an increased flow of pancreatic juice, while the secretion is suppressed in the dog, though not in the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance o
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