400 ADVANCED PHYSIOLOGY 



CHAPTER II 



Page 27. Show the class some charcoal, graphite (" lead " of a lead 

 pencil), and some lampblack, calling attention to the fact that they are 

 the same chemical element, carbon. Light a bit of candle and cover with 

 a bell glass. The candle soon goes out. Explain that the carbon has 

 combined with the oxygen in the air to form a new compound, CO 2 or 

 carbon dioxid. 



Show the class specimens of phosphorus, sodium, potassium, iron and 

 sulfur. Place a little sulfur in an earthen dish and ignite it. It burns 

 with a blue flame and gives off a suffocating gas. It has combined with 

 the oxygen of the air, forming by oxidation a new compound, SO 2 or sulfur 

 dioxid. 



Page 29. Tests should be made on a variety of common foods to 

 prove the presence of proteid. White of egg, meat juice, ground oat- 

 meal, show the test readily. With a solution of any one of them in water 

 in a test tube (use 10 cc. or so) add a little strong nitric acid and heat to 

 boiling ; note the yellow color. Add ammonia, and note the orange 

 color (Xanthoproteic reaction). 



With rather weak solution of same material in test tube, add a little 

 1% sol. copper sulfate, then a little caustic potash; a violet color shows 

 presence of proteid. 



Try same reagents with starch and sugar solutions, and show that the 

 tests are negative. 



The gluten content of flour can be shown by putting a quantity of 

 flour in a muslin bag and thoroughly kneading it in a pail of water. Much 

 of the bulk will wash out into the water ; the gluten will be left as a sticky, 

 undissolved mass in the bag. 



Pour a little hydrochloric acid into a small amount of milk. The 

 curd which forms is largely casein. 



Fibrin can be obtained from perfectly fresh blood by stirring it. The 

 fibers which catch on the object used in stirring are fibrin. 



Myosin can be shown in finely minced lean meat by soaking it in a 

 little water for a few hours, and then pouring strong acid (nitric) into some 

 of the juice. The material which coagulates is myosin. 



Page 31. (a) Shake up a little corn or potato starch with water in 

 test tube and add a few drops of an iodine solution. A typical blue- 

 color reaction will appear. Ground rice, flour, and cereal also respond 

 readily. Use the same test on white of egg or sugar solution to prove 

 validity of test. 



