216 



THE CIRCULATION OF THE BLOOD AND LYMPH 



bottle so as to increase the rate of flow of the water, and repeat the 

 observations. The ' circulation-time ' will be found to be diminished. 

 This corresponds to an increase of blood-pressure due to increased 

 activity of the heart, without change in the calibre of the bloodvessels. 

 Next, leaving the bottle in its present position, diminish the outflow 

 by tightening the clamp; the circulation -time will be increased. This 

 corresponds to an increase of blood-pressure due to diminution in the 

 calibre of the small arteries. 



(&) Fill the syringe* with methylene-blue solution (o - 2 per cent, in 

 o'9 per cent, salt solution), as in (a). Keep the solution warmed to 

 40 C. by immersing the small beaker containing it in a water-bath, or 



pig 107. Artificial Scheme to illustrate a Method of measuring the Circulation- 

 Time. B, bottle containing water, the rate of outflow of which is regulated by 

 screw -clamp a ; S, syringe filled with methylene-blue solution, connected with 

 T -piece A; M, beaker containing methylene-blue solution; b, c, screw -clamps; 

 C, T-piece, inserted in the course of the flexible tube E, and connected with the 

 glass tube T, which is filled with beads; F, outflow tube. The clamp c having 

 been closed and 6 opened, the syringe is filled with the methylene-blue solution ; 

 6 is then closed, c opened, and a definite quantity of the solution injected into the 

 system. The time from the beginning of injection till the appearance of the blue 

 at G is measured with the stop-watch. 



heating it over a bunsen with a small flame. Weigh a rabbit or cat. 

 In the case of the rabbit, inject grm. chloral hydrate into the rectum, 

 and later on give ether if necessary. If a cat, give ether alone. Fasten 

 it on a holder, back downwards (Fig. 61, p. 136). Cover it with a 

 towel to keep it warm. Clip off the hair on the front of the neck, and 

 make an incision ij inches long in the middle line, beginning a little 



* A burette, sloped so as to make a small angle with the horizontal, may 

 be substituted for the syringe. The burette is supported on a stand at such 

 a height (say 10-15 cm. above the level of the cannula) that the methylene- 

 blue solution runs without great force into the jugular. The danger of pro- 

 ducing an abnormal result by suddenly raising the pressure in the right side 

 of the heart is thus avoided. 



