80 BEHAVIOUR OF GASTEIC JUICE TOWARDS REAGENTS. [BOOK II. 



Besides the enzymes we have mentioned, and more or less 

 extraneous admixture with mucus, some fat, and organic products of 

 digestion, the gastric juice contains alkaline chlorides, earthy phos- 

 phates, and iron. No experiments have been made to determine the 

 presence or nature of any gases which it may hold in solution or 

 feeble combination. 



Various re- ^he fU wm g ar some of the principal characters 

 actions exhi- of pure gastric juice of the dog 1 . 



bited by the It is not coagulated on boiling, which however 



gastric juice. destroys its proteolytic properties. The acid juice is, 

 according to some, coagulated by ferrocyanide of potassium, though 

 the evidence on this point is not unanimous. 



Concentrated mineral acids produce no turbidity, or precipitate. 



Alkaline carbonates throw down a scanty precipitate, consisting 

 mainly of earthy salts, carrying down with them, however, a portion 

 of the organic matter, although the filtrate, when acidulated, still 

 retains digestive powers. 



Sodium chloride, when added to saturation, precipitates many of 

 the albumoses which the juice contains, together with a large part of 

 the ferments. 



Mercuric chloride produces a precipitate, which contains a part, 

 but not the whole, of the pepsin present. 



Silver nitrate precipitates the chlorides and hydrochloric acid 

 present, and likewise a part of the pepsin. 



Lead salts, as lead acetate, form precipitates containing a great 

 part of the pepsin. From this precipitate much of the pepsin may 

 be separated by mere washing with water. 



Alcohol produces a white precipitate, which, if the quantity of 

 alcohol added be not excessive, slowly dissolves in water, yielding 

 a solution which when acidulated with hydrochloric acid, digests 

 actively. When a large excess of alcohol is however added to the 

 gastric juice, the precipitate is said by Frerichs to lose for ever 

 its digestive properties. 



Results of Before examining, in detail, the facts which are 



analyses ex- known concerning the ferments and the acid of the 



nibiting the gastric juice, and their relation to the process of 



general com- digestion, the attention of the reader is drawn to the 



position of the f n owm or often quoted analysis, exhibiting the general 



gastnc juice. .=>. f ,? , / ^ j TVT 



composition of the gastric juice of the dog. JNo complete 



and at the same time reliable analysis of the gastric juice of man is 

 available 2 , however there is no reason for supposing that the secretion 

 in man is sensibly different from that of the dog. 



1 Frerichs, Article 'Verdauung' in Wagner's Handworterlntch, Vol. in. p. 785. 



2 There is a constantly quoted analysis of the gastric juice of a woman, made 

 by C. Schmidt, which the author cannot admit as satisfactory inasmuch as the free 

 acid which it reveals is at least ten times below that which is now known to be present 

 in healthy human gastric juice. 



