236 . DIGESTION. 



to represent the whole twenty-four hours, or by ascertaining the amount of fluid required 

 to digest a certain weight of food and estimating from this the quantity necessary to dis- 

 pose of all the food taken during the day. Both of these methods are manifestly incor- 

 rect. In the first, the intermittency of the secretion is not taken into account ; and, in 

 the second, it is incorrectly assumed that digestion out of the hody is accomplished pre- 

 cisely as it takes place in the stomach. 



Dr. Beaumont was sometimes able to collect, in from ten to fifteen minutes, two 

 ounces of pure gastric juice, simply by the stimulation produced by the gum-elastic 

 catheter used in the operation ; but he expressly states that, in this case, only a part of the 

 mucous membrane is excited to secretion, while the flow is very much increased by the 

 introduction of food by the mouth, which produces a general excitation of the secreting 

 membrane. Estimates like those of Bidder and Schmidt, which put the quantity of gas- 

 tric juice secreted in twenty-four hours by a healthy man of ordinary size at six thou- 

 sand four hundred grammes, or about fourteen pounds, are probably not exaggerated, 

 although they are of necessity merely approximative. 



The enormous quantity of fluid daily secreted by the mucous membrane of the stom- 

 ach would excite surprise were it not considered that, after this fluid has performed its 

 office in digestion, it is immediately reabsorbed, and but a small quantity of the secretion 

 exists in the stomach at any one time. During digestion, a circulation of material is 

 going on, in which the stomach is continually producing, out of materials furnished by 

 the blood, a fluid which liquefies certain elements of the food and, as fast as this is ac- 

 complished, is absorbed again by the blood, together with the principles that have been 

 thus digested. 



Composition of the Gastric Juice. 



The gastric juice is mixed in the stomach with more or less mucus secreted by the 

 lining membrane. When drawn by a fistula, it generally contains particles of food, which 

 have become triturated and partially disintegrated in the mouth, and is always mixed 

 with a certain quantity of saliva, which is swallowed during the intervals of digestion as 

 well as when the stomach is in a state of functional activity. By adopting certain pre- 

 cautions, however, the fluid may be obtained nearly free from impurities, except the ad- 

 mixture of saliva. 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 fluid, of 

 a faint yellowish or amber tint, and possessing little or no viscidity. Its reaction is 

 always strongly acid ; and it is now a well-established fact that any fluid, secreted by 

 the mucous membrane of the stomach, which is either alkaline or neutral, is not the nor- 

 mal gastric juice. 



The specific gravity of the gastric juice in the case of St. Martin, according to the 

 observations of Beaumont and Silliman, was 1005 ; but later, Dr. F. G. Smith found it 

 in one instance, 1008, and in another, 1009. There is every reason to suppose that the 

 fluid, in the case of St. Martin, was perfectly normal, and from 1005 to 1009 may be 

 taken as the range of the specific gravity of the gastric juice in the human subject. 

 There is undoubtedly considerable variation, as regards specific gravity, in the inferior 

 animals. 



The gastric juice is described by Beaumont as inodorous, when taken directly from 

 the stomach ; but it has rather an aromatic and a not disagreeable odor when it has been 

 kept for some time. It is a little saltish, and its taste is similar to that of "thin, mu- 

 cilaginous water slightly acidulated with muriatic acid." The gastric juice from the dog 

 has something of the odor peculiar to this animal. 



It has been found by Beaumont, in the human subject, and by those who have experi- 

 mented on the gastric juice of the lower animals, that this fluid, if kept in a well- 

 stoppered bottle, will retain its chemical and physiological properties for an indefinite pe- 

 riod. The only change which it undergoes is the formation of a pellicle, consisting of a 



