294 RESP1RA TION 



2.* Production of Apncea and Periodic Breathing in Man. Arrange 

 for taking tracings of the respiratory movements from a fellow-student 

 as in i. Let the subject of the experiment recline in a perfectly easy 

 position in an armchair. Let him then breathe deeply and frequently 

 for about two minutes, so as to produce a prolonged apncea of about 

 two minutes' duration. Whenever any desire to breathe returns, the 

 breathing is to be allowed to take its own course. It may be expected 

 at first to be of the psriodic (Cheyne-Stokes) type. 



3. Tracing of the Respiratory Movements in Animals. (a) Set up 

 the arrangement shown in Fig. 135, and test whether it is air-tight. 

 Have also in readiness an induction machine and electrodes arranged 

 for an interrupted current. Anaesthetize a rabbit with chloral or 

 ether (p. 216), or a small dogf with morphine and ether, or A.C.E. 

 mixture. Insert a cannula into the trachea (p. 199), and connect it 

 with the large bottle by a tube. Connect the bottle with a recording 



Fig. 134. Stethograph. 



tambour adjusted to write on a drum, and regulate the amount of the 

 excursion of the lever by slackening or tightening the screw-clamp. 

 Set the drum off at slow speed, and take a tracing. 



(b) Then disconnect the cannula from its tube. Dissect out the 

 vagus in the lower part of the neck, pass a ligature under it, but do not 

 tie it. Connect the cannula again with the bottle, and while a tracing 

 is being taken ligature the vagus. Cut below the ligature and stimulate 

 its central end with weak shocks, marking the time of stimulation on 

 the drum. Repeat the stimulation with strong shocks, and observe 

 the results. 



(c) Apply a strong solution of potassium chloride with a camel's- 

 hair brush to the central end of the vagus while a tracing is being taken, 

 and observe the effect. 



* This experiment is only to be attempted under the direct supervision of 

 the demonstrator. 



f If a large dog is used the bottle should be omitted, the tracheal cannula 

 being connected with the stem of a T-tube. One end of the horizontal limb 

 of the T-tube is connected with the tambour; the other is provided with a 

 rubber tube, which can be partially closed by a screw-clamp to regulate the 

 excursion. Ether may be given when required by connecting the horizontal 

 limb of the T-tube with a bottle with two glass tubes in the cork (p. 199). 



