132 THE DIGESTIVE FLUIDS. 



and extracting the fatty acids with ether. The chymosin remains in 

 aqueous solution, and may now be precipitated with strong alcohol. 

 It is then rapidly collected on a filter and dried. 



Quantitative Estimation of Chymosin and Chymosinogen. As in 

 the case of pepsin and pepsinogen, relative values only can be 

 obtained. The gastric juice is neutralized with a very dilute solu- 

 tion of sodium hydrate. Tubes are then prepared, containing 5 or 

 10 c.c. of the gastric juice, variously diluted in the proportion of 

 1 : 10, 1 : 20, 1 : 30, etc., to which an equal volume of neutral or 

 amphoteric milk is further added. These tubes are kept at a 

 temperature of from 37 to 40 C., when the degree of dilution is 

 noted at which coagulation still occurs. Under normal conditions 

 a positive reaction can thus be obtained in man with a degree of 

 dilution varying between 1 : 30 and 1 : 40. 



In the case of the zymogen, the gastric juice is rendered feebly 

 alkaline, when tubes are prepared as just described. Normally a 

 positive reaction can thus still be obtained with a dilution varying 

 between 1 : 100 and 1 : 150. 



Other Constituents of the Gastric Juice. Of other con- 

 stituents, the gastric juice normally contains traces of sulpho- 

 cyanides, which are secreted by the stomach itself; a variable 

 amount of mucin ; a small amount of coagulable albumin, or, if the 

 fluid has stood for some time, a corresponding quantity of albumoses 

 or peptones, and, as already shown, certain mineral salts. 



The gases which are found in the stomach have in part been 

 swallowed with the food. A small portion is further referable to 

 eructations from the duodenum, while a third portion is probably 

 secreted by the stomach itself. This is true more especially of 

 the carbon dioxide, and Schierbeck has shown that the tension 

 of this gas gradually increases from 30 to 40 Hgnim. while 

 fasting, to 130 to 140 Hgmm. during the process of digestion, 

 and is apparently directly proportionate to the acidity of the 

 gastric juice. 



An idea of the relative amounts of the gases which are normally 

 found in the stomach may be formed from the accompanying table, 

 which is taken from Planer : 



Man. Dog. 



Vegetable diet. Veg. diet. Meat diet, 



vol. percent. vol. per cent. vol. per cent. 



Carbon dioxide 20.79-33.83 32.9 25.2 



Oxygen ' . 0.37 , . 0.8 6.1 



Nitrogen 72.50-33.22 66.3 68.7 



Hydrogen 6.71-27.58 . . 



Other gases, such as marsh gas, olefiant gas, ammonia, and hy- 

 drogen sulphide, are found only under pathologic conditions, and 

 are referable to certain fermentative and putrefactive changes which 

 take place in the ingested food. 



