RESPIRATION 



195 



the arrangement of the ribs, intercostal muscles, and connected parts 

 should be noticed. When the thorax is cut open the lungs collapse. 

 Observe the relation of the heart to the lungs. Innate the latter 

 through a tube inserted in the trachea. Observe the diaphragm; 

 note its shape in contraction and relaxation. Cut open the lungs and 

 trace out in them the subdivisions of the bronchial tubes. The struc- 

 ture of the trachea and larynx should be carefully studied. 



84. To illustrate the Action of the Diaphragm in Respiration. Tie 

 over the large end of a stoppered bell jar, or of a large bottle whose 



bottom has been removed, a 

 piece of thin rubber cloth 

 (Fig. 104). Close the smaller 

 opening of the jar with a 

 cork, through which runs a 

 glass tube, on whose inner end 

 a thin rubber bag is tied, as 

 shown in the figure. Then, if 

 the rubber bottom be pushed 

 in, the bag will collapse. 

 When the bottom is allowed 

 to return to its first position, 

 the bag expands. The rub- 

 ber bottom represents the dia- 

 phragm, and the small rubber 

 bag and the glass tubing the 

 lungs and trachea, while the /rflTi 

 jar itself represents the tho- 

 rax. If the lungs and trachea of a small animal be 

 carefully dissected out, they may be used to replace 

 the small rubber bag by tying the glass tube in the 

 trachea. In this way may be shown the movements 

 of the lungs themselves in respiration. Another form 

 of apparatus for demonstrating the action of the 

 diaphragm in respiration is shown in Fig. 105, in 

 which the bell jar and rubber cloth of Fig. 104 are 

 replaced by a lamp chimney and a piston. (The 

 piston can be made of a wooden stick with a piece 

 of wet cloth tied around the large end.) 



85. To illustrate the Function of the Ribs in Respiration. Construct a 



Fig. 104. Apparatus 

 to illustrate the 

 action of the dia- 

 phragm in respira- 

 tion. 



Fig. 105. 



Apparatus to de- 

 monstrate the 

 action of the 

 diaphragm in 

 respiration. 



