DIGESTION. 193 



absence of the rennet enzyme, as above stated, may occur in many 

 cases (BOAS, JOHNSON, KLEMPERER). In regard to the acid, it 

 should be mentioned that sometimes this secretion may be in- 

 creased so that an abnormally acid gastric juice is secreted, and 

 sometimes may be decreased so that little or hardly any hydro- 

 chloric acid is secreted. A hypersecretion of acid gastric juice 

 sometimes occurs. In the secretion of too little hydrochloric acid 

 the same conditions appear as after the neutralization of the acid 

 contents of the stomach outside of the organism. Fermentation 

 processes now appear in which, besides lactic acid, there appear also 

 volatile fatty acids, such as butyric and acetic acids, etc., and gases 

 like hydrogen. These fermentation products are therefore often 

 found in the stomach in cases of chronic catarrh of the stomach, 

 which may give rise to belching, heart-burn, and other symptoms. 

 Among the foreign substances found in the contents of the 

 stomach we have UREA, or ammonium carbonate derived there- 

 from in uraemia; BLOOD, which generally forms a dark-brown mass 

 through the presence of haematin, due to the action of the gastric 

 juice ; BILE, which, especially during vomiting, easily finds its way 

 through the pylorus into the stomach, but whose presence seems to 

 be without importance. 



If it is desired to test the gastric juice or the contents of the 

 stomach for pepsin, fibrin may be employed. If this is thoroughly 

 washed immediately after beating the blood, well pressed and 

 placed in glycerin, it may be kept in serviceable condition an inde- 

 finitely long time. The gastric juice or the matter contained in the 

 stomach the latter, if necessary, having been previously diluted 

 with 1 p. m. hydrochloric acid, is filtered and tested with fibrin at 

 ordinary temperature. (It must not be forgotten that a control test 

 must be made with acid alone and another porton of the same 

 fibrin.) If the fibrin is not noticeably digested within one or two 

 hours, no pepsin is present, or at most there are only slight traces. 



In testing for rennet enzyme the liquid must be first carefully 

 neutralized. To 10 cc. unboiled amphoteric (not acid) reacting 

 cow's milk add 1-2 cc. of the filtered neutralized liquid; but care 

 must be taken not to add too much of the liquid from the stomach, 

 for the coagulation may be retarded or prevented by diluting the 

 milk. In the presence of rennet the milk should coagulate to a 

 solid mass at the temperature of the body in the course of 10-20 

 minutes without changing its reaction. If the milk is diluted too 

 much by the addition of the liquid of the stomach, only coarse 



