33 



B. Carbohydrates. 



Test orig-inal solution for starch. 



Then saturate thoroughly with ammonium sulphate 

 (crystals). Starch and g-lycog-en, if present, are pre- 

 cipitated, together with proteids. Dextrin, if present, 

 will remain in solution. Filter, and save precipitate(a) 

 and filtrate (&). 



(a) Wash precipitate on filter with small portions 

 of a saturated solution of ammonium sulphate till por- 

 tions of washing-s give no trace of dextrin. (In testing- 

 washings for dextrin dilute each time with an equal 

 volume of water). When washings are entirely free 

 from dextrin pass two or three cc. of water (cold) 

 through filter and test for glycogen wi^ a single drop 

 of iodine. A red brown or mahogany color results if 

 glycogen is present. Basic lead acetate- precipitates 

 glycogen but not dextrin. 



(b) Dilute filtrate (b) with an equal volume of 

 water and test for dextrin. 



Test original solution for reducing sugars — first precipi- 

 tating out the proteids with acetic acid and sodium sulphate 

 and boiling. 



VII 

 SALIVARY DIGESTION 



- 102. The saliva is a mixture of the secretions of the par- 

 otid,, submaxillary, and sublingual glands with that of the 

 glands of the membrane of the mouth. The reaction of the 

 mixed saliva is usually alkaline but may on fasting, also dur- 

 ing the night toward morning, and 2-3 hours after meals, or 

 after much talking, become acid. On standing some hours it 

 may become acid and a film of calcium carbonate form on the 

 surface. The normal mixed saliva contains inorganic con- 

 stituents consisting of : carbonates, chlorides, sulphates, and 

 nitrites of magnesium, calcium, potassium, and sodium, also 

 the sulphocyanide of potassium. The nitrites and sulpho- 

 cyanide are often absent. The organic constituents are albu- 

 min, mucin, and ptyalin. The ptyalin has the power to convert 



