162 DIGESTION. 



for example, we have found in one instance, like Dr. Beaumont, that the 

 gastric j uice was always entirely absent in the intervals of digestion ; 

 the mucous membrane then presenting invariably either a neutral or 

 slightly alkaline reaction. In this animal, which was a perfectly healthy 

 one, the secretion could not be excited by any artificial means, such as 

 glass rods, metallic catheters, and the like ; but only by the natural 

 stimulus of ingested food. Tough and indigestible pieces of tendon, 

 introduced through the fistula, were expelled again in a few minutes, one 

 after the other, without exciting the flow of a single drop of acid fluid ; 

 while pieces of fresh meat, introduced in the same way, produced at 

 once an abundant supply. Jn other instances, on the contrary, the 

 introduction of metallic catheters or glass rods into the empty stomach 

 has produced a scanty flow of gastric juice ; and in experimenting upon 

 dogs that have been kept without food during various periods of time 

 and then killed by section of the medulla oblongata, we have usually, 

 though not always, found the gastric mucous membrane to present a 

 distinctly acid reaction, even after an abstinence of six, seven, or eight 

 days. There is at no time, however, under these circumstances, any 

 considerable amount of fluid present in the stomach ; but only sufficient 

 to moisten the gastric mucous membrane, and give it an acid reaction. 



The gastric juice which is obtained by irritating the stomach with a 

 metallic catheter is clear, perfectly colorless, and acid in reaction. A 

 sufficient quantity of it cannot be obtained by this method for any 

 extended experiments; and for that purpose, the animal should be fed, 

 after a fast of twenty-four hours, with fresh lean meat, a little hardened 

 by short boiling, in order to coagulate the fluids of the muscular tissue, 

 and prevent their mixing with the gastric secretion. No effect is usually 

 apparent within the first five minutes after the introduction of the food. 

 At the end of that time the gastric juice begins to flow ; at first slowly, 

 and in drops. It is at first perfectly colorless, but soon acquires a 

 slight amber tinge. It then begins to flow more freely, usually in drops, 

 but often running for a few seconds in a continuous stream. In this 

 way, from 60 to 75 cubic centimetres may be collected in the course of 

 fifteen minutes. Afterward it becomes somewhat turbid with the debris 

 of the food, which has begun to be disintegrated ; but from this it may 

 be readity separated by filtration. After three hours, it continues to 

 run freely, but has become very much thickened, and even grumous in 

 consistency, from the abundant admixture of alimentary debris. In six 

 hours after the commencement of digestion it runs less freely, and in 

 eight hours has become very scanty, though it continues to preserve the 

 same physical appearances as before. It ceases to flow altogether in 

 from nine to twelve hours, according to the quantity of food taken. 

 For purposes of examination, the fluid drawn during the first fifteen 

 minutes after feeding should be collected, and at once separated by 

 filtration from accidental impurities. Obtained in this way it repre- 

 sents, as closely as possible, the normal constitution of the gastric juice 

 as secreted by the stomach during the digestive process. 



