LABORATORY EXERCISES 413 



piece of hard soap. See list of dealers for source of modeling wax ; such 

 material is often used in grade schools or kindergartens. 



Page 214. Use can be made here of a tuning fork. If it is struck 

 and the stem of it placed on the side of a hollow wooden box open at one 

 end (or on a regular resonator), the combined effect of the vibration of 

 the tuning fork and of the air chamber will be marked. The text sugges- 

 tion of talking into different sizes of air containers should be carried out. 



CHAPTER XIV 



Page 219. The kidney of a sheep or pig is best adapted to show 

 structure ; that of calf or beef is not similarly constructed. Show the 

 capsule about the kidney, and then split it open by cutting from the 

 convex side toward the ureter. The cortex and medullary regions, pyra- 

 mids, etc., are readily noted. 



By use of a cat, or rabbit, the ureters, bladder, and urethra can be 

 plainly demonstrated. 



Page 221. Prepared slides of injected kidney should be examined 

 and Malpighian capsules containing glomeruli noted. The tubules will 

 be seen in cross and longitudinal section, though none will be found com- 

 plete. 



CHAPTER XV 



Page 228. Prepared slides of skin show practically all the points 

 mentioned. A student should prove that a needle thrust into the epider- 

 mis causes no pain or bleeding. 



The subcutaneous tissue holding the skin to the outer muscle layers 

 of the body is easily demonstrable in any small animal, e.g. cat, rat, 

 white mice, or any which may be obtainable. 



Page 235. Examine the skin with a simple magnifier and compare 

 the markings of different fingers. Let one pupil be blindfolded and various 

 parts of his skin tested with points of dividers. Scissors, firmly gripped, 

 may very well be used in same way. Determine how near together they 

 may be and yet be felt as two. Test the fingers, the back of the hand, 

 the arm, the forehead, and back of the neck. 



The determination of hot and cold spots requires too much apparatus 

 for class use. However, interesting results are secured in the following 

 manner : Have at hand two bowls, one containing quite warm water, the 

 other cool water. Put finger of one hand into the warm water, a finger 

 of other hand into the cool water. Is there a difference in sensations? 

 After holding thus for a. minute, place both in lukewarm water ; what 

 is the result? Try to explain why. 



