THE CIRCULATION OF THE BLOOD 553 



experiment on the volume of contracting muscle, 

 Fig. 58). Place the middle finger in the cylinder, 

 making sure that the rubber collar fits around 

 the finger tightly, but without impeding the 

 venous circulation. Close the side branch. 



Periodical alterations in the volume of the 

 finger will be recorded ; they have the rhythm of 

 the heart-beat. (The friction of the writing-lever 

 must be very slight to insure success, and the 

 curve at best will be small.) 



Determine the effect of straining and forced 

 respiration upon the curve. 



APPARATUS 



Normal saline. Bowl. Towel. Pipette. Artificial 

 scheme. Microscope. Mesentery board. Mercury man- 

 ometer. Aortic cannula. One per cent solution of sodic 

 carbonate. Ligature. Glass rod one inch long. Frog- 

 board. Wooden stand. Kymograph. Inductorium. Dry 

 cell. Electrodes. Key. Electromagnetic signal. Sphyg- 

 mograph with large anu small thistle-tubes. Rubber 

 membrane. Bone collar-button. Heart-holder. Screw- 

 clamp. Muscle lever with scale-pan and weights. Stand. 

 Fine copper wire. Tortoise with heart exposed. Ice. 

 Solution of sodium chloride, 0.7 per cent. Solutions of 

 calcium chloride, and potassium chloride, each isotonic 

 with 0.7 per cent solution of sodium chloride. A solu- 

 tion containing sodium chloride, 0.7 per cent ; calcium 

 chloride, 0.026 per cent; and potassium chloride, 0.035 

 per cent. Binaural stethoscope. Nitrite of amyl. Pl- 

 thysmograph. 



