RESPIRATION 125 



(d) Respiration in C0 2 ("Choke-damp"). (17) Lower a lighted 

 candle into a jar of CO 2 . Record results. 



(18) What happened to the animal when it was lowered into an 

 atmosphere of CO 2 ? 



(19) Record post-mortem appearances. 



(e) Respiration in an Atmosphere of One -third Illuminating Gas 

 (CO+). Record all symptoms. 



Record post-mortem appearances. 



How does death in an atmosphere of CO compare, as to symptoms, 

 with death in an atmosphere of CO 2 . 



Compare it in turn with other forms of death as induced in this 

 and the previous chapter. 



Compare the post-mortem appearances in this case with those in 

 preceding cases. 



X. TO DETERMINE THE INFLUENCE OF THE PHRENIC NERVE. 

 THE NORMAL PHRENOGRAM. 



1. Appliances. Operating case; clippers; rabbit board or dog 

 board; rabbit or dog; ether or chloroform; anaesthesia cone; tambours, 

 arranged as used to record the rabbit stethogram; beaker with warm 

 water; inductorium; one dry cell; two keys; vagus electrode; seven 

 wires; a piece of glass rod 10 cm. which has been rounded at one 

 end and sharpened at the other. 



2. Preparation. Fix the animal to the board; anaesthetize; clip 

 the anterior median region of abdomen. Set up electric apparatus 

 with short-circuiting key in secondary coil and with Neef hammer 

 in primary circuit. 



3. Operation. From the posterior extremity of the xiphoid 

 appendix make a median incision through the abdominal walls. 

 The incision should be just large enough to admit the glass rod, and 

 should be located in the rabbit 1 cm', from the tip of the xiphoid 

 and in the dog 3 cm. from the xiphoid. 



Clamp with the serre-fines any small vessels which may be 

 oozing. 



The rounded end of the glass rod is passed through the abdom- 

 inal wall and held against the diaphragm A. The point is 

 inserted into the cork button of the receiving tambour. (See 

 Fig. 65.) Any contraction of the diaphragm presses the round end 

 backward and the rod is forced posteriorly, slipping back and forth 

 through the hole in the body wall, the point is pressed back, and the 

 lever of the recording tambour rises. Trace a phrenogram. 



In the mean time let another member of the division dissect out 

 the left phrenic nerve. 



This operation to expose the phrenic nerve is the most difficult 



