PROPERTIES AND COMPOSITION OF GASTRIC JUICE 193 



dance from the stomach. It was noted, also, that the sight, odor, or 

 even idea of food, particularly in animals having a " passionate longing," 

 excited a flow of juice. The secretion thus obtained, Pawlow called 

 psychic juice. He found also that all the digestive excretions were 

 much increased in quantity when the appetite was good and food was 

 relished. According to these observations, "the properties of the 

 juice correspond with the requirements of the food. The starch- 

 holding diet receives a juice rich in amylolytic ferment, the fat-contain- 

 ing, a juice with much fat-splitting ferment. This is manifest from the 

 strength of the juice, but still more so from the absolute quantities of 

 the ferment." 



It has long been known that impressions made on the gustatory 

 nerves have a marked influence in exciting the action of the mucous 

 membrane of the stomach ; and that in most animals, particularly when 

 they are very hungry, the sight and odor of food often will set up a 

 secretion of both saliva and gastric juice. Febrile conditions, the de- 

 pression resulting from an excess in eating and drinking, and even 

 purely mental conditions, such as anger or fear, vitiate, diminish and 

 sometimes entirely suppress secretion by the stomach. At some times, 

 under these conditions, the mucous membrane becomes red and dry, 

 and at others it is pale and moist. 



After the food has been in part liquefied and absorbed and in part 

 reduced to a pultaceous consistence, the secretion of gastric juice 

 ceases ; the movements of the stomach having gradually forced that 

 portion of the food which is but partially acted on in this organ or 

 is digested only in the small intestines out at the pylorus. The stomach 

 is thus entirely emptied, the mucous membrane becomes pale, and its 

 reaction loses its acid, character, becoming neutral or faintly alkaline. 



Quantity of Gastric Juice. Data for determining the quantity of 

 gastric juice secreted in the twenty-four hours are so uncertain that it 

 seems impossible to fix on any estimate that can be accepted even as 

 an approximation. Still, the quantity must be considerable, in view of 

 the large amount of alimentary matter acted on in gastric digestion. 

 It probably is not less than six pounds (2.72 kilograms) or more than 

 fourteen pounds (6. 3 5 kilograms). After this secretion has performed 

 its office in digestion, it is reabsorbed, and but a small quantity exists in 

 the stomach at any one time. 



Properties and Composition of Gastric Juice. The juice taken from 

 the stomach during the first moments of. its secretion and separated 

 from mucus and foreign matters by filtration is a clear liquid, of a faint 

 yellowish or amber tint and possessing little or no viscidity. Its reac- 

 tion is always strongly acid. The specific gravity of the gastric juice 



