388 A MANUAL OF PHYSIOLOGY 



The action of alcohol on the secretion of gastric juice has been 

 studied in a dog with a double gastric and oesophageal fistula. 

 Before or during a sham meal of meat, alcohol diluted with water 

 was given as an enema. After the enema the quantity of hydro- 

 chloric acid secreted increased in about the same proportion as the 

 quantity of juice, but the pepsin was diminished, reaching a mini- 

 mum after three-quarters to one and a quarter hours. The increase 

 in the total quantity of the juice and in the acid over-compensated 

 the moderate diminution in the digestive power, so that the net 

 result was beneficial (Pekelharing) . But it must be remembered 

 that strong alcoholic beverages, when mixed with the gastric juice, 

 and therefore when taken by the mouth, retard the prpteolytic 

 action, so that any favourable effect on the secretion of the juice may 

 easily be lost in the subsequent digestion, unless the alcohol is dilute 

 (Chittenden and Mendel) . The action of alcohol introduced into the 

 rectum on the gastric secretion is both reflex and direct. 



Cholagogues. The action of a host of drugs on the secretion of bile 

 has been investigated by various observers, but till something like 

 unanimity has been reached it would not be profitable to go into 

 details here. The only real cholagogues at present positively known 

 appear to be the salts of the bile-acids, which, given by themselves 

 or in the bile, cause not only an increase in the volume of the biliary 

 secretion, but also an increase in its solids. Certain compounds of 

 salicylic acid, as salol (phenyl salicylate) and sodium salicylate, also 

 appear to slightly increase the flow, while usually diminishing the 

 concentration of the bile. The injection of haemoglobin into the 

 blood-stream, or its liberation there by substances, such as toluylene- 

 diamin and arseniuretted hydrogen, which cause destruction of the 

 corpuscles, leads to an increased secretion of bile-pigment as well as 

 a more rapid flow of bile. 



Summary. Here let us sum up the most important points 

 relating to the secretion of the digestive juices. They are all 

 formed by the activity of gland-cells originally derived from the 

 epithelial lining of the alimentary canal. The organic constituents 

 or their precursors (including the mother -substances of the ferments) 

 are prepared in the intervals of rest absolute in some glands, 

 relative in others and stored up in the form of granules, which 

 during activity are moved towards the lumen of the gland tubules, 

 and there discharged. 



The nerves of the salivary glands are, as regards their origin, 

 (a) cerebral, (b) sympathetic ; the former group is vaso-dilator , the 

 latter (usually) vaso-constrictor ; both are secretory. Secretion of 

 saliva depends strictly on the nervous system. That nerves influence 

 the gastric and pancreatic secretions is also made out. The psychical 

 secretion is of greater importance for the saliva and gastric juice 

 than for the pancreatic juice. The direct action of secretin (pro- 

 duced in the intestinal mucous membrane by the influence of the 

 chyme) is the most characteristic factor in pancreatic secretion. 

 As regards the intestinal glands and the liver, it has not been 

 proved that their secretive activity is under the control of the nervous 

 system, except in so far as the latter may indirectly govern it through 



