ORGANS OF THE BODY. 483 



nature. It has been held at different times to be either lactic or hydro- 

 chloric, without taking into account a number of other ill-founded 

 theories. The matter has been at last set at rest, however, by C. Schmidt, 

 in favour of the latter view. Lactic, acetic, and butyric acids may, 

 however, be present as decomposition products, the first being indeed 

 a very frequent constituent of gastric juice. O g 02 per cent, of hydro- 

 chloric acid was discovered by Schmidt in the gastric juice of a female, 

 and 0'305 per cent, by Bidder in that of the dog. 



The ferment found in the gastric juice is known as pepsin. It was 

 many years ago made the object of very extended investigation by 

 Schwann and Wasman, and since then by many other observers, but can 

 hardly be said to have ever been obtained completely pure. Its propor- 

 tion generally amounts to about, on an average, 1 per cent. Bidder and 

 Schmidt's analyses give 1'75 for the dog. 0'42 for the sheep, and for man 

 only 0'319 per cent. At present but little is known of pepsin as about 

 all the other fermenting substances of the animal economy. "We are 

 aware, indeed, that it occurs in a soluble form, is precipitated by alcohol 

 without losing its digestive power on subsequent re-solution in water, 

 whilst elevation of temperature above 60 C. destroys this for ever. This 

 pepsin, as has been shown by Frericlis, is the granular matter seen m 

 the contents of the peptic glands. It appears to possess almost unlimited 

 digestive properties in the presence of an adequate amount of dilute acid, 

 so that there seems to be an inexhaustible store of it in the mucous 

 membrane of the stomach. 



The mineral constituents of the gastric juice are, chlorides of the 

 alkalies, phosphatic earths, and phosphate of iron (Bidder and Schmidt). 

 Among the first we find a great preponderance of common salt, and 

 besides chlorides of potassium, of calcium, and of ammonium also. We 

 shall take an analysis by the two last named observers as an example of 

 the proportions of the various salts. The percentage in the gastric juice 

 of the dog was as follows : Chloride of sodium, 0'251 ; of calcium, 0'062 ; 

 of potassium, 0'113; of ammonium, 0*047; phosphate of magnesium, 

 0-023 ; of calcium, 0'173 ; of iron, O'OOS. 



Just as the peptic cell is able to produce pepsin from an albuminous 

 substance, so also does it yield hydrochloric acid by the splitting up 

 possibly of the chlorides. This process, however, is probably carried on 

 only at the undermost portion of the gland tubule, i.e., near the orifice 

 (Brilcke), the source of the watery fluid with its salts being the long- 

 meshed capillary network of the peptic glands. 



The amount of gastric juice poured out is naturally very variable, 

 owing to the periodical nature of the functions of the stomach, and 

 therefore necessarily difficult to determine. It is stated by Bidder and 

 Schmidt to be at all events very considerable. A dog of about a 

 kilogramme weight produces, in the course of a day, about 100 grammes, 

 with extremes in both directions. Schmidt estimated the amount 

 secreted hourly in the body of a woman at the enormously high figure 

 of 580 grammes. 



The use of this fluid is to dissolve the albuminous matters taken into 

 the stomach, and to convert them into peptones, i.e., modifications of 

 these substances which neither coagulate at boiling point or under the 

 action of mineral acids, nor combine with metallic salts to form insoluble 

 compounds (Lehmann). They transude, on the other hand, with great 

 readiness through animal membranes, a property of the utmost import- 



