92 EXPERIMENTAL PHYSIOLOGY 



8. Inject into the jugular vein a few drops of an extract of ox- 

 pituitary. The extract is made in the same way as the suprarenal 

 extract. The posterior lobe only should be used. Notice the effect of 

 the extract upon the blood-pressure and upon the plethysmograph 

 record. If the injection is repeated after a short interval, most of the 

 results are not shown, or are much less marked. 



9. Kill the animal by asphyxia which may be effected by occlud- 

 ing the trachea or by allowing carbon monoxide gas (or coal gas) to be 

 respired. A continuous tracing showing the effects of asphyxia, both 

 upon the respiratory movements and upon the blood-pressure and 

 heart beats, may be recorded. 



The pulmonary circulation. The blood-pressure in the pulmonary 

 artery may most easily be obtained by the use of a specially constructed 

 cannula which is passed into the commencement of the artery, through 

 the ventral wall of the right ventricle. The cannula, filled with half- 

 saturated bicarbonate of soda solution, is tied in the wall of the ventricle 

 by a purse-string suture and is furnished with a plug, to prevent escape 

 of blood while it is being inserted. Its construction will be understood 

 from the diagram (Fig. 73). It is connected with a vertical glass tube, 

 with scale attached (Fig. 74), which serves as a manometer, giving the 

 pulmonary pressure in centimetres and millimetres of the solution. The 

 pressure is recorded upon the blackened paper of the kymograph, by a 

 piston-recorder connected with the open end of this manometer, and is 

 written down simultaneously with the pressure in the systemic arteries 

 recorded by the mercurial manometer. 



As the thorax has to be opened to expose the heart and insert the 

 pulmonary cannula, artificial respiration must be maintained through- 

 out (p. 76). 



