LABORATORY MANUAL OF PHYSIOLOGY. 



reagent, which is already made up. This is a solution of mercu- 

 rous nitrate together with some free nitrous acid. When mixed 

 with proteid a yellow precipitate is formed which becomes red on 

 heating. 



2. To Differentiate Albumins, Proteoses, and Peptones. 

 (a) What reactions have they in common ? Are the albumins co- 

 agulable by heat? Are the proteoses coagulated D> neat? Are 

 the peptones coagulated by heat ? 



(b) Do the proteoses give a precipitate with nitric acid? Do 

 the peptones? 



(c) To a proteose solution add some potassium ferrocyanid acid- 

 ified with acetic acid. Is there any precipitate? Repeat with a 

 pure peptone solution. Is there any precipitate ? 



(d) To a solution of proteoses add sodium chlorid to satura- 

 tion. Is there any precipitate ? Repeat with pure peptone solution. 



(e) To a peptone solution add alcohol. Is a precipitate formed ? 

 Repeat using a saturated solution of tannic acid instead of the 

 alcohol. Result ? 



3. Artificial Gastric Juice. Scrape off the mucous membrane 

 of the fresh stomach of a pig. Grind this thoroughly with clean 

 sand in a mortar. Add ten times the volume of a o.2-per-cent so- 

 lution of hydrochloric acid and place in the incubator at blood 

 temperature for twenty-four hours. 



Grind up another portion of mucous membrane of the pig's 

 stomach with glycerin. Let this stand for several days before 

 using. 



(a) To a little fibrin in a test-tube add some o.2-per-cent HC1. 



(b) To another portion of fibrin add some of the glycerin ex- 

 tract of the pig's stomach. 



(c) To another portion of fibrin add some of the acidulated 

 aqueous extract of pig's stomach. 



(d) To another portion add some of the acidulated extract 

 which has been neutralized and made slightly alkaline with so- 

 dium carbonate. 



(e) To another portion add some glycerin extract plus enough 



