DIGESTION. 677 



two hours, transfer to absolute alcohol for one hour, and then to ether for an 

 hour; then collect on a filter and dry between filter-paper. The proteose thus 

 obtained is a mixture of primary and secondary proteoses. 



Use an aqueous solution of this proteose for the following tests : Acidulate 

 a portion with acetic acid and add an equal volume of saturated solution of 

 sodium chloride. The solution becomes cloudy, clearing again when heat is 

 applied, and becoming cloudy again when cool. (Characteristic of proteoses.) 

 Other portions of the solution use for the xanthoproteic, Millon's, and biuret 

 reactions. 



Proteoses will give positive precipitation tests with acetic acid and ferro- 

 cyanide, and with trichloracetic acid. Peptones will give negative results with 

 the same tests. 



To obtain peptone, the filtrate from the proteose is heated and 20 grammes 

 of ammonium sulphate are added to remove traces of proteose. The filtrate, 

 after being concentrated by evaporation, is treated with barium carbonate, 

 alcohol and ether, exactly as directed above for proteose. Use some of the 

 peptones for the xanthoproteic, Millon's, and biuret reactions. 



Clinical examination of gastric juice. The chemical examina- 

 tion of gastric juice, or of contents of stomach, is now considered of 

 great importance in the diagnosis of diseases of the stomach. The 

 juice for examination is obtained as follows : On an empty stomach, 

 the patient partakes of a test-meal, consisting usually of bread and 

 water, and an hour after or later (depending upon the form of meal 

 administered) the contents of the meal are withdrawn by means of a 

 stomach-tube. The liquid is filtered and used for further examina- 

 tions. These examinations consist of the following determinations : 

 a. reaction ; b. presence of free acids ; c. presence of free hydro- 

 chloric acid ; d. presence of lactic and other organic acids ; e. total 

 acidity ; /. estimation of free acids ; g. estimation of free hydrochloric 

 acid ; h. estimation of combined hydrochloric acid ; i. estimation of 

 total organic acids ; j. presence of pepsin and pepsinogen ; k. presence 

 of renuin and rennin zymogen ; I, detection of proteins ; m, detection 

 of carbohydrates. 



In case a sufficient supply of gastric juice cannot be obtained for the reac- 

 tions below, the student should prepare the following solutions : A. A 0.25 per 

 cent, hydrochloric acid ; B. A mixture of 10 parts of A and 40 parts of water; 

 C. A solution of 0.8 gramme of lactic acid in 100 c.c. of water ; D. A 2 per 

 cent, solution of albumose in water. Make reactions b and c with solution A, 

 repeat with B, and with a mixture of 1 part of B and 2 parts of D. 



a. Reaction. This should be, and in all normal juices is, distinctly 

 acid to litmus-paper. 



6. Free acids. The presence of free acids is detected by congo-red 

 paper. This paper is prepared by soaking unsized paper in a 1 per 

 cent, aqueous solution of congo-red, and drying. If a drop of juice 



