230 



THE CIRCULATION OF THE BLOOD 



scribed for irrigating it with fluid in the preceding experiment. Connect 

 it up in a Roy's tonometer, see figure 213, adjust the lever of the tonometer 

 for a tracing on the smoked paper of the recording cylinder. Use a time- 

 marker. This instrument records the change in volume with each heart 



FIG. 213. Roy's Tonometer. 



contraction. The influence of pressure, varied between 2 and 10 cm., and of 

 nutrient fluids on the heart volume may be determined. 



7. The Isolated Heart of the Terrapin. The heart of the terrapin, 

 being somewhat larger and somewhat more responsive than the heart of the 

 frog, may be substituted in the two immediately preceding experiments. 

 The facts obtained from it will be essentially the same as those obtained 

 from the frog's heart. 



8. The Isolated Mammalian Heart. The mammalian heart 

 may be isolated from the body and kept alive and contracting for many 

 hours, as has been demonstrated by numerous recent observations. It is 

 only necessary to keep the temperature approximately that of the normal 

 body and to irrigate the hear: through the coronary circulation with blood, 

 or diluted blood, containing sufficient hemoglobin to supply the heart with 

 the requisite amount of oxygen. Or, the heart may be kept alive on the inorganic 

 salt solutions, provided these are supplied with oxygen under considerable 

 tension (Porter, Howell). Even the human heart has been isolated and 

 kept contracting for seme hours in the above manner (Kuliabko). The 

 method used is to insert a supply cannula into the aorta and irrigate the heart 

 through the coronary circulation, as described by Langendorff. Many in- 

 teresting experiments and demonstrations can be made on the mammalian 



