PART II. 



SPECIAL PHYSIOLOGY. 



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CHAPTER III. 

 THE CIRCULATION OF THE BLOOD. 



I. THE CAPILLARY CIRCULATION AND THE MOVEMENTS OF 



THE HEART. 



A. To Observe the Capillary Circulation. 



1. Appliances. Frog; microscope, with low-power and high- 

 power objective; cork board 10 cm. wide by 20 cm. or 30 cm. long 

 and J cm. thick; pins; operating case; normal saline solution; watch- 

 glasses; two 100 c.c. beakers. 



2. Preparation. Pin the frog out, dorsum up, upon a cork board, 

 and bring one hind foot over a hole 1 cm. in diameter cut in the 

 corner of the board with a cork borer. By tying a thread to the second 

 and third toes the web between these holes may be stretched over 

 the hole in the board. Care should be taken not to stretch the web 

 too tightly and thus impede the circulation. 



Fix the cork board with the frog upon the stage of the microscope 

 in such a manner as to bring the stretched web over the middle of 

 the stage. Illuminate the web and focus under a lower power. 

 Keep the web moist. 



3. Observations. (1) Observe the movement of corpuscles within 

 bloodvessels of varying size and irregular course. Make a drawing 

 of the field of observation showing the relative size, the course, and 

 anastomoses of the bloodvessels. 



(2) Observe whether the motion is equally rapid in all vessels; 

 if not, observe whether the slower currents are in the larger or the 



aller channels. Determine which of the vessels are arterioles, which 

 capillaries, and which venules. 



(3) Have you seen evidence of intermittent force acting upon 

 the corpuscles? If so, describe its influence. Determine whether 

 this intermittent force makes itself evident in all the vessels; if not, 

 in w r hich class of vessels is it present? 



