THE GASTRIC JUICE. 325 



163, The Gastric Juice. 



Properties The gastric juice is a tolerably clear colourless fluid, 

 with a strong acid reaction, sour taste, and peculiar characteristic odour; 

 it rotates the plane of polarised light to the left (Hoppe-Seyler). It is 

 not rendered turbid by boiling, and resists putrefaction for a long time. 

 Its specific gravity = 100 2 '5 (dog, 1005), and it contains only 1 p.c. of 

 solid constituents. The quantity of gastric juice secreted in 24 hours 

 was estimated by Beaumont, from observations upon Alexis St. Martin, 

 who had a gastric fistula (1834) at only 180 grms. daily (!); by 

 Griinewald (1853), in a similar case, as equal to 26'4 p.c. of the body- 

 weight; while Bidder and Schmidt (from corresponding observations on 

 dogs) estimated it as equal to 6 J kilos, daily, corresponding to ^ of the 

 body-weight. It contains : 



(1.) Pepsin (Th. Schwann, 1836), the characteristic nitrogenous 

 hydrolytic ferment or enzym, which dissolves proteids 3 per 1000. 



(2.) Hydrochloric Acid (Prout, 1824), 0-2-0-3 (according to Kichet, 

 0'8-2 ! 1) per 1000; (in the dog. 15 times more). This occurs free in the 

 gastric juice, as the latter always contains more free chlorine than 

 bases, to which it can be united (C. Schmidt). Lactic acid is usually 

 met with, but it arises from the fermentation of the carbohydrates of 

 the food. 



[It has been for a long time disputed, whether the acidity of the gastric juice is 

 due to hydrochloric acid or to free lactic acid. The most reliable of recent methods 

 for determining this, point conclusively to hydrochloric acid as the cause of the 

 acidity (Richet and others).] 



Tests Free hydrochloric acid is detected by the following reactions: 0'025 

 p.c. solution of methyl violet becomes blue; or, alkaline solution of tropaeolin 

 becomes lilac; or, red Bordeaux wine is treated with amylic alcohol until its colour 

 almost disappears when, if dilute hydrochloric acid be added, a rose colour is 

 obtained. 



(3.) The large amount of mucus which covers the surface of the 

 mucous membrane is to be regarded as the secretion from the goblet 

 cells of the mucous membrane (p. 321). [The reaction of the mucus 

 covering the walls of the empty stomach is in many cases alkaline 

 (M. Hay).] 



(4.) Mineral Salts (1 per 1000). 



They are chiefly sodium a d potassium chlorides, less calcic chloride (ammonium 

 chloride, also in animals), , nd the compounds of phosphoric acid with lime, 

 magnesium, and iron. 



Amongst foreign substances, which may be introduced into the body, the follow- 

 ing appear in the gastric juice, J1I, after the use of potassium iodide potassium 

 sulpho-cyanide, ferric lactate, ani sugar, and ammonium carbonate in uraemia. 



