114 THE DIGESTIVE FLUIDS. 



After standing for some time the supernatant fluid is poured off, and 

 the blue sediment dissolved in 150 c.c. of dilute aeetic aeid. The 

 solution is kept in a sealed hot tie. 



Extractives. Of extractives, normal saliva contains a small 

 amount of urea, and traces of cholesterin, lecithin, and leucin. In 

 polity conditions uric acid has been found; sugar, the biliary pig- 

 ments, and biliary acids are not eliminated through the saliva.* 



Mineral Constituents. The mineral constituents of saliva con- 

 sist to the extent of 90 to 92 per cent, of soluble salts, among which 

 the chlorides greatly predominate, and of about 6 per cent, of salts, 

 which are principally represented by the carbonates and phosphates 

 of calcium and magnesium, which *are held in solution by the free 

 carbonic acid of the saliva. In addition, a trace of iron is found. 

 Following the administration of bromides and iodides a notable 

 elimination of these salts occurs through this channel. 



Gases. Of gases, which are present in a state of solution, we 

 find about 20 c.c. for every 100 grammes of saliva. Of these, 19 

 c.c. are represented by carbon dioxide, while oxygen and nitrogen 

 together amount to only 1 c.c. 



THE GASTRIC JUICE. 



General Considerations. The gastric juice is the secretory 

 product of the glandular structures of the stomach, and the only 

 digestive fluid which presents an acid reaction. In pure form it is 

 best obtained from animals after ligating the ducts of the salivary 

 glands and establishing a fistulous opening on the outer abdominal 

 walls. If the mucous membrane is then appropriately stimulated, 

 a clear or but slightly opalescent yellowish fluid is obtained, which 

 has a very characteristic odor and a strongly acid reaction. Its 

 density varies between 1.001 and 1.010. 



On microscopic examination are found epithelial cells from the 

 lining of the glandular ducts, goblet-cells, mucous corpuscles, free 

 nuclei, and a variable number of bacteria. In addition, we often 

 observe small tapioca-like bodies, which under the microscope are 

 seen to contain numerous formations resembling snail-shells, and 

 which probably consist of altered mucin. 



Amount. Of the total amount of gastric juice secreted in the 

 twenty-four hours, but little is known. Its secretion is influenced by 

 numerous factors, such as the appetite, the quality and quantity of 

 the food ingested, the age and sex of the individual, the time of day 

 (notably in relation to the taking of food), the various emotions, etc. 

 According to Bidder and Schmidt, the amount corresponds to about 

 one-tenth of the body-weight, so that a man weighing 70 kilo- 

 grammes would secrete about 7000 grammes in the twenty-four 

 hours. This figure, however, I regard as too high, and am inclined 

 to place the amount at from 2000 to 3000 c.c. 



The non-digesting stomach of the dog and other animals is said 



