LESSON XX. 



THE STRUCTURE OF THE LUNG. THE 

 MECHANICS OF RESPIRATION. 



1. CUT off the head of a newt. Cut through the 

 skin in the median ventral line of the body, and 

 expose the lungs. Cut across the aorta. Pass a 

 silk thread under the anterior part of one lung 

 and underneath the thread and lung place a 

 small piece of cardboard. Seize with fine 

 scissors a small part of the wall of the lung and 

 snip it with fine pointed scissors, then, pressing 

 a glass cannula somewhat against the underlying 

 cardboard introduce it into the hole made in the 

 lung. Tie the silk thread tightly around the 

 neck of the cannula. With a pipette fill the 

 cannula with 0'5 p.c. gold chloride solution, and 

 pressing it on a small piece of india-rubber 

 tubing which has been previously fitted to the 

 cannula, distend, but not too strongly, the lung ; 

 on raising the cannula and alternately pressing 

 and leaving free the indiarubber tube, any air- 

 bubbles which may be in the lung will pass into 

 the cannula. Clamp the tubing in such a way as 



142 



