APPENDIX. 249 



ascends, the lung collapses, and air is forced out of it (expiration). 

 Then open the air tube leading into the bell-jar. The lung will col- 

 lapse, and the movements of the diaphragm have no influence 

 upon it. 



10. The diaphragm itself may be readily seen on the body of any 

 small animal (rat, kitten, puppy), on removing the abdominal vis- 

 cera. The liver and stomach must be cut away with especial care. 



a. When the above viscera are removed the vaulted diaphragm 

 will be seen, and through it the pink lungs. 



b. Seizing some of the folds of peritoneum attached to the dia- 

 phragm, pull it down, imitating its contraction and flattening in in- 

 spiration. The lungs will be seen to follow it closely, expanding to 

 fill the space left by it in its descent. 



c. Make a free opening into one side of the thorax. The corre- 

 sponding lung will collapse, and be no longer influenced by move- 

 ments of the diaphragm. 



d. Now open the other side of the chest: its lung also shrinks up; 

 the structure of the diaphragm (its tendinous centre and muscular 

 peripheral regions) can now be better seen, as also the attachment of 

 the pericardium to its thoracic side. 



11. The action of the microscopic cilia in driving along the mucus 

 in which they move may be demonstrated as follows: 



a. Cut off a frog's head and destroy its spinal cord (p. 230) 

 Then cut out its gullet as completely as possible; slit this open and 

 spread it out, inner side up, on a piece of cork or board, and fix it 

 with pins stuck through its edges. 



b. Prepare a very thin and small shaving of cork. Dissect the 

 skin off one thigh of the animal and wrap a bit of it round the shav- 

 ing of cork, with its underside outwards. 



c. Place the light mass thus formed on the mucous membrane of 

 the gullet, near its mouth end. The little mass will slowly be moved 

 along to the stomach end of the gullet, and if returned to the mouth 

 end time after time will be swept along in the same direction. This 

 is due to the cilia which line the frog's gullet (they are not present 

 In that of man), and push along to the stomach the mucus bathing 

 them on which the little float swims. 



d. Place the exposed gullet under a bell- jar with a wet sponge for 

 an hour or two. The mucus secreted by it will be found to have 

 been swept along to the end of it which joins the stomach. 



