ADVANCED EXPERIMENTAL PHYSIOLOGY 157 



Action of Chloroform and Ether. Excise two frogs' hearts and 

 place each in a watch glass containing 5 c.c. of Ringer's fluid. To 

 one add one drop of pure chloroform and cover with another watch 

 glass. The heart will become feeble, lose tone, and finally stop 

 beating. It will take considerably more ether to produce the 

 same effect on the other heart. The causation of death from 

 chloroform is cardiac failure. In the mammal the arterial pressure 

 falls, and the vagus centre is rendered hyperexcitable by too con- 

 centrated a dose of chloroform. Failure of respiration and syncope 

 result from inhibition and poisoning of the heart. 



By Molecules. By Weight. By Volume. 



Alcohol ... 1 1 1 



Ether .... 8 5 5 



Chloroform ... 100 40 75 



The relative physiological powers of alcohol, ether and chloroform. (Waller.) 



CHAPTER XXXI 



PERFUSION OF THE VENTRICLE OF THE FROG'S 

 HEART 



The Symes cannula is fastened into the auricles by a thread 

 passed over the dorsal surface of the aortic bulb and tied in the 

 sinu-auricular groove. The side tube of the cannula is connected 

 with the perfusing fluid, which is pumped by the ventricle through 

 the aorta and streams downwards over the surface of the heart. 

 The ventricular beat is recorded by a lever connected to the apex 

 by a light clip. 



With this method determine the effects of distilled water, normal 

 tap-water saline or Ringer's fluid (Fig. 149) and of the drugs men- 

 tioned in the previous chapter. 



CHAPTER XXXII 

 VASO-MOTOR SYSTEM OF THE FROG 



Innervation of the Blood-vessels. Place a frog on the cork board 

 provided for studying the circulation in the web. Observe the 

 rate of the circulation in the web of foot. Destroy the nervous 

 tissues in the cranium and the medulla. The circulation will 

 become more rapid owing to dilatation of the arteries. 



Now remove the frog from the board and expose the heart. 

 Suspend the frog in the vertical head-up position. Note that the 

 heart and large vessels are filled with blood. Pass a blanket -pin 

 down the vertebral canal and destroy the spinal cord. The heart 

 and vessels will soon become bloodless owing to the loss of vaso- 

 motor tone. The blood sinks into the dilated abdominal vessels 

 under the influence of gravity. 



