LABORATORY EXERCISES 



409 



Page 145. Count the pulse rate ; then run up stairs and down, or 

 50 yards and back, and make recount of the rate. Try effect of holding 

 the breath. 



Page 147. A permanent preparation of a frog with arteries injected 

 is purchasable, and very suggestive for the study given here. If laboratory 

 work is given, fill arteries with starch mass (see formula), by injecting 

 forward through the truncus .arteriosus (big vessel leaving the heart), 

 tying off both toward the heart before injecting, and beyond injection 

 point after injecting. See addresses of firms selling injection syringes, etc. 



Page 148. Circulation may be shown as follows : Bore a hole one- 

 half inch in diameter through one end of a piece of thin, softwood board. 

 The cover of an ordinary chalk box will serve. Etherize a frog till wholly 

 unconscious ; wrap it in cheesecloth (to aid in handling) except one hind 

 leg. Bind the frog to the board, letting the web of the free foot lie over 

 the hole. Pin out the web so that it will be lightly stretched over the 

 hole, and then place on stage of compound microscope, so that light will 

 shine through the web. Capillaries of various sizes will be seen, with 

 blood flowing in them. 



Page 149. These large blood vessels have probably been seen in 

 the course of the demonstration for page 137, but can be further shown 

 by use of a model of the heart. 



Page 151. Prepared sections of arteries and veins should be shown 

 under the microscope. 



CHAPTER XI 



Page 155. Arrange a rubber tube in horizontal position, with a 

 capillary glass tube in one end and syringe bulb at the other. In the 

 middle of the tube insert a glass T, and from this side branch let a glass 

 tube lead vertically ; its upper end should be open. On pumping in water 

 with the syringe the pressure will be evident from the height to which 

 water rises in the vertical branch. If the capillary at the end of the hori- 

 zontal tube be removed, scarcely any pressure will be produced, 



