the tempers 



LABORATORY EXERCISES [403 



temperature of the body and let it stand for about ten minutes. 

 Then test for sugar. A typical reaction should appear. The sweet taste 

 of bread (a starchy food), after being in the mouth for a while is well 

 known. 



Examine saliva under a microscope to note the absence of any fermenting 

 bodies, like yeast. 



Page 67. 1. To see yeast cells, examine a mixture of yeast and water 

 with a microscope (high power) . 



2. Set aside, in a warm place, any food material such as piece of meat, 

 in small receptacle ; barely cover with water, and leave for two or three 

 days. Then examine a drop, covered, under microscope with high powers, 

 for numerous forms of bacteria. They have almost no color, and much 

 care must be used in having just the right degree of illumination. 



With a dull edged instrument (e.g. spoon handle) scrape a little material 

 from inside lining of the cheek, or take a little material from between the 

 teeth with tooth-pick; place this in a little water under cover-slip and 

 examine as above. Bacteria will be numerous, perhaps loose epithelial 

 cells also. 



Page 73. Fill four test tubes one-third full of water. Place in two 

 of them a small bit of meat and in the other two a little white of egg. 

 Plug all four with cotton. Place one of each set of two in a beaker of 

 water and boil briskly for ten minutes. Set all four aside. Examine after 

 two days and again after four days. 



Many bacteria will appear in the unboiled tubes, with characteristic 

 decomposition odors ; the boiled tubes will show no deterioration. 



CHAPTER V 



Page 76. 1. A human skull should be at hand for direct reference 

 to the teeth. Separate teeth to show roots, etc., can usually be obtained 

 from a dentist. Other skulls containing teeth are useful to show differ- 

 ent shapes in animals of different habits. Teeth of a rabbit or horse are 

 very different from those of a carnivorous animal, e.g. cat or dog. 



2. The layers of a tooth can be easily shown by use of prepared sections. 

 See list of dealers in slides. 



A model of a tooth can be rather easily cut from piece of hard soap. 



Page 77. Dip a bit of blue litmus paper into a little dilute hydro- 

 chloric acid, and note that it turns red. In the same way test vinegar, 

 lemon juice, and sour milk. Dip a bit of red litmus paper into an alkaline 

 liquid, like ammonia. Test soapsuds in the same way. Determine whether 



liva is acid or alkaline. 



saliva is aci< 



