ANIMAL FLUIDS AND TISSUES. 359 



sulphocyanate, as may be shown by the addition of a drop of 

 ferric chloride solution, which produces a deep red color, disap- 

 pearing on the addition of mercuric chloride (difference from 

 meconic acid). 



Gastric juice is a liquid secreted by the follicles of the stomach ; 

 it has always a decidedly acid reaction, due to free hydrochloric 

 acid, which is most likely formed by the action of sodium phos- 

 phate on calcium chloride : 



2(Na 2 HPO 4 ) + 3CaCl 2 = Ca 3 2PO 4 -f 4NaCl + 2HC1. 



Sodium Calcium Calcium Sodium Hydrochloric 



phosphate. chloride. phosphate. chloride. acid. 



According to others the hydrochloric acid is liberated by. the 

 action of acid sodium carbonate on sodium chloride : 



NaHCO 3 + NaCl = Na 2 CO 3 + HC1. 



Sodium Sodium Sodium Hydrochloric 



acid carbonate. chloride. carbonate. acid. 



The above formulas show the reverse action of that which 

 these substances exert upon each other under common con- 

 ditions, but it must be remembered that the living cell is 

 capable of decomposing matter generally in a manner different 

 from that which it suffers ordinarily. 



Gastric juice contains of: 



Water, 99.460 per cent. 

 Pepsin, 0.302 " 



Free hydrochloric acid, 0.022 " 



Alkaline chlorides, 0.200 " 



Phosphates of calcium, -| onifi 



magnesium, andiron, / 



Pepsin, the most important constituent of gastric juice, has 

 been spoken of heretofore; it has, in the presence of free hydro- 

 chloric acid the power of converting proteids into peptones; 

 it does not act on starch, but does not prevent the continued 

 action of saliva on it ; acting on fats, it dissolves the albuminous 

 envelopes of the fat cells, but does not act chemically upon the 

 fats themselves. 



Bile, secreted by the liver, is a thin, transparent liquid of a 

 golden-yellow color, and a specific gravity of 1.020; it has a 



