ACTION OF ETHER OX THE HEART 71 



and fourth vertebrae. Their beats cannot be observed from 

 the exterior.) Count the rate of lymph heart beats and 

 also the rate of the blood heart beats. (These can be seen 

 beneath the skin of the chest.) If the frog breathes also 

 count the rate of respiration. (How does a frog breathe?) 

 Now place the frog under a battery jar and deeply anes- 

 thetize it with chloroform. Remove the animal and again 

 count the rate of beats of the heart, of the posterior lymph 

 hearts (do these beat synchronously?), and the rate of 

 respiration. What conclusions can you draw? Are these 

 results due to a central or a peripheral action of the chloro- 

 form? (How is the beating of the lymph-hearts controlled? 

 How is this mechanism provided for in the mammal?) Al- 

 low the frog to recover and observe its symptoms. How 

 long before the frog becomes normal again? 



EXPERIMENT III. 



Turtle: Vagus Dissection. (Action of Ether on the 



Heart.) 



1. Pick up a turtle and draw its head forward out of the 

 shell. This may be done with a wire having a short sharp 

 hook on one end. The hook is passed between the carapace 

 and plastron and hooked into the anterior angle of the 

 lower jaw below. Draw out the head and seize it between 

 the first and second fingers of the left hand. Clasp the 

 hand around the turtle's neck and pith it with a sharp 

 probe or hat pin in the same way that the frog is pithed. 

 It as advisable to pith the cord also by pushing a soft brass 

 or iron wire down the spinal canal. The wire is intro- 

 duced through the same opening by which the animal's 

 brain was destroyed. 



Catch the turtle's lower jaw in the hook of a turtle board 

 (Fig. 28) in the manner shown in Fig. 67. Pull the hind 

 legs outward and backward firmly and forcibly and fasten 

 them to the board. This may be done with strings (heavy) 



