52 



PHYSIOLOGY FOR THE LABORATORY. 



Take a long, deep inspiration, hold the breath, and 

 measure again. 



Give some idea of the difference in cubic capacity, which 

 this difference in circumference represents. 



D. Models to Illustrate the Principles of Breathing. 



NOTE. Adapted from Hints for Teachers of Physiology by 

 Professor Bowditch. 



I. THE VERTICAL ENLARGEMENT OF THE THORAX. 



Apparatus. A glass bottle without the bottom, or a lamp- 

 chimney. A piece of rubber dam about half an inch larger than 

 the lower part of the chimney. A toy rubber balloon used by. small 

 boys, called a " squawker," or another piece of 

 rubber dam about six inches in diameter. A 

 rubber stopper, with two holes in it, to fit the 

 upper end of the chimney. About twelve inches 

 of glass tubing to fit the holes in the stopper. 

 A pinch-cock. Linen thread. Three inches of 

 rubber tubing to fit the glass tubing. A stout 

 rubber band. 



The apparatus should be put together 

 very carefully, as in Fig. 7, to prevent 

 FIG. 7. A model to the escape of air. 



show the vertical , 



enlargement of the # J-he chimney represents the chest 



thorax. 



b. With an elastic band fasten over the lower end of 

 the chimney a piece of rubber dam to represent the 

 diaphragm. 



c. Into the upper end of the chimney fit the rubber 

 stopper containing two pieces of glass tubing, each bent at 

 a right angle. Attach the toy balloon (or the trachea and 



