52 QUANTITY OF GASTRIC JUICE. 



The hydra, a fresh-water polype, may be taken as the type of this organ- 

 ism. This animal, Fig. 7, consists of a bag or digestive sac, a a, end- 

 ing in a cylinder, #, the opening to which is furnished with numerous 

 tentacles, c c c ; the tentacles enfold in their grasp objects on which the 

 hydra feeds, and by their contractions carry them to the sac. Into the 

 interior of the sac a juice exudes possessing digestive powers, and soon 

 dissolving food. 



We may therefore regard the follicular structure of the stomach as a 

 colony of polypes, the tentacles of which are converged into a muscular 

 tube, constituting the oesophagus. In a stomach of ordinary size there 

 are probably a million of these organisms. Digestion is undoubtedly 

 conducted on the same physical principles in both cases, though in the 

 polype the food matter enters the follicular cavity of which the body of 

 the animal consists, but in man is contained in the stomach, into which 

 the follicles open, and pour forth their digestive fluid. 



With respect to the acid constituent of the gastric juice, it appears to 

 be hydrochloric or lactic. The latter has probably originated in the man- 

 ner just described by the action of the saliva on amylaceous bodies ; the 

 former undoubtedly comes from the common salt ingested. Perhaps, un- 

 der a deficiency of common salt, lactic acid discharges the entire duty. 

 Schmidt regards the digestive principle as a conjugated acid, the nega- 

 tive constituent being hydrochloric acid, and pepsin being the adjunct, 

 the compound being analogous to ligno-sulphuric acid. About twenty 

 Quantity of parts of gastric juice are required to digest one part of dry al- 

 gastric juice. ]oumen, and about 70 ounces are secreted in a day. If the 

 hourly destruction of fibrin in average muscular action is 62 grains, about 

 60 ounces of gastric juice would be required each day for muscular repair. 

 A very large demand is therefore made upon the water in the system for 

 this use. But here the same remark is to be made as in the case of the 

 saliva ; the water, after accomplishing its object, is not lost to the econ- 

 omy, but is immediately reabsorbed. 



It was remarked, in speaking of the salivary glands, that their secre- 

 Re eated as ** on P asses repeatedly through them, the saliva, as it exudes, 

 sage of extra- being swallowed, reabsorbed, and so secreted over and over 

 through the a g am ' ^ n these repeated passages, many salt substances, 

 stomach foiii- such as the iodide and bromide of potassium, will accompany 

 it, the kidneys, however, eventually removing such extraneous 

 bodies. In like manner, heterogeneous matters will make a repeated cir- 

 culation through the gastric follicles before a final removal by the kid- 

 neys. When the latter organs have been extirpated, the constituents of 

 their secretion, such as urea, may appear in the stomach. 



On the deposit of the food in the stomach, a movement of translation 

 is given to it by the alternate contraction and relaxation of the fibres of 



