ELEMENTS OF THE BODY 31 



DEMONSTRATIONS 



3. Illustrate the properties of albumin by the white of an egg. 

 Notice its sticky character. Dry some upon a piece of paper over a 

 fire and notice its brittle, gluelike character, and that it will again dis- 

 solve in water. Boil some and notice that it becomes hard and will 

 not redissolve. Set some aside and notice that it decays. 



4. Inclose a lump of wet flour in a muslin bag and wash it until the 

 water is clear. This removes the starch grains and leaves the grain 

 albumin or gluten pure. Notice its tough and sticky character. 



5. Show samples of olive oil, lard, and tallow. Show that lard 

 melts at about the temperature of the body, and so is fluid in the body. 



6. Shake together some oil and water. Notice that the oil at once 

 floats upon the surface. Now shake the oil with some lime water, and 

 notice that it no longer floats, but that the mixture looks milky, while a 

 few very small oil drops can be seen floating in the liquid. Explain 

 that this is an emulsion. 



7. Stir together some castor oil and caustic soda, gently heating the 

 mixture, and notice that it forms soap. 



8'. Scrape a potato into a basin of water. Wash it about and notice 

 that the shreds of potato will float, while a white substance will settle 

 to the bottom of the basin. Explain that this substance is starch, and 

 that our great-grandmothers used this method to make starch for 

 laundering. 



9. Place a small drop of the wet potato starch upon a glass slide 

 and examine it with a power of at least 50 diameters. Notice that the 

 starch grains appear like oyster shells. Examine also some corn starch 

 and notice that each grain looks like an irregular cube with a star-shaped 

 center. Sketch the starch grains. 



10. Boil some starch and notice that it swells and forms a jellylike 

 paste. 



Iodine turns starch blue. Apply a drop of the tincture of iodine to 

 the starch and notice the blue color. Apply it to bread, cake, flour, 

 etc. Notice the blue color, showing that they all contain starch. 

 Notice that meat does not respond to the test. 



n. Show specimens of sugar. Brown sugar is the impure form, 

 while granulated sugar is the pure crystallized form. Show some sugar 

 scraped from the outside of raisins and explain that this is glucose or 

 grape sugar, and that all sugar and starch must be changed into this 

 form before it can be used by the body. 



