144 THE DIGESTIVE FLUIDS. 



positive reaction can thus still be obtained with a dilution varying 

 between 1 : 100 arid 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 mticin ; 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 Hgmm. 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. per cent. 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. 



THE PANCREATIC JUICE. 



As has been pointed out, the digestive glands which have so far 

 been considered are not essential to the maintenance of life. The 

 salivary glands and the stomach can in certain animals be elimi- 

 nated without seriously interfering with the process of digestion, 

 and the ferments which in man are secreted by these structures 

 are in many animals absent. The pancreas, on the other hand, 

 either as such or as a so-called hepatopancreas, is found in all 

 vertebrate and invertebrate animals in which the process of diges- 

 tion is carried on in a well-defined digestive tube. In many, 

 indeed, it represents the only digestive gland of the body. Its 

 removal, even in the higher animals, invariably leads to death. In 

 dogs, in which this operation has been repeatedly performed, and in 

 which life may go on for a few weeks thereafter, it has been 



