DIGESTION 347 



by a substance like gamboge, there is no increase in the 

 rate of secretion of the bile, notwithstanding the greatly 

 increased flow of blood through the intestinal vessels which 

 the irritation causes. This tells in favour of the direct 

 influence of substances derived from the food rather than 

 of any important reflex action. 



(5) The Influence of Nerves on the Secretion of Intestinal 

 Juice. As to the influence of nerves on the secretion of the 

 succus entericus, our knowledge is almost limited to a single 

 experiment, and that an inconclusive one. Moreau placed 

 four ligatures on a portion of the small intestine, so as to 

 form three compartments separated from each other and 

 from the rest of the gut. The mesenteric nerves going 

 to the middle loop were divided, and the intestine returned 

 to the abdomen. After some time a watery secretion was 

 found in the middle compartment, little or none in the 

 others. This is a true ' paralytic ' secretion, and not a 

 mere transudation depending simply on the vascular dilata- 

 tion caused by section of the vaso-constrictor nerves, for it 

 has the same composition and digestive action as normal 

 succus entericus obtained from a fistula. 



Effect of Drugs on the Digestive Secretions. A small dose of 

 atropia, as has been said, abolishes the secretory action of the chorda 

 tympani. This it does by paralyzing the nerve endings. The gland- 

 cells are not paralyzed, for the sympathetic can still cause secretion. 

 The nerve-fibres are not paralyzed, because the direct application of 

 atropia does not affect them ; nor is the seat of the paralysis the 

 ganglion-cells on the course of the fibres, for stimulation between 

 those cells and the gland-cells is ineffective. Pilocarpine is the 

 physiological antagonist of atropia, and restores the secretion which 

 atropia has abolished. In small doses it causes a rapid flow of 

 saliva, its action being certainly a peripheral action, and probably an 

 action on the nerve-endings, for it persists after all the nerves going 

 to the salivary glands have been divided, and after the ganglion-cells 

 have been paralyzed by nicotine. Atropia and pilccarpine act 

 similarly on some of the other digestive glands, the former paralyzing 

 the pancreatic secretion, the latter increasing the secretion of gastric, 

 and probably of intestinal, juice; but atropia does not stop the 

 secretion caused by division of the intestinal nerves. Physostigmine 

 and muscarine act on the whole like pilocarpine. 



The action of a host of drugs on the secretion of bile has been 

 investigated by various observers, but till something like unanimity 

 h<it) been reached, it would not be profitable to go into details here. 



