ACTION OP THE DIAPHRAGM AND THE LUNGS. 75 



slender or short and clumsy? Does the 

 animal, therefore, seem to be adapted for 

 swift or for slow locomotion? Give rea- 

 sons for your answer. 

 E. Teeth. 



28. What is the dental formula (number of in- 



cisors, canines, grinders in each half- 

 jaw) ? 



29. Did the animal probably eat animal or vege- 



table food? Reason for answer? 



38. ACTION OF THE DIAPHRAGM AND THE 

 LUNGS. (Dem.) 



Procure a bell-jar with an opening at the top for a stopper. Place 

 a marble in the centre of a sheet of rubber, tie the rubber about it, 

 and stretch the sheet of rubber over the larger end of the bell- jar, 

 tying tightly. Secure a rubber stopper (provided with two holes) 

 which will fit the opening in the top of the bell-jar. Pass a thistle- 

 tube through one of the holes in the rubber stopper and tie a toy 

 balloon to its lower end. Through the other hole pass a glass tube, 

 attaching to the upper end a piece of rubber tubing closed with 

 a clamp. Insert the rubber stopper in the opening at the top of the 

 bell-jar with the toy balloon within the jar. Make sure that all con- 

 nections are tight, by applying paraffin to the top surface of the cork. 



The balloon represents a lung; the thistle-tube to which it is tied, 

 the larynx and windpipe; while the bell-jar itself represents the 

 chest-cavity, and the sheet rubber the diaphragm. 



A. Exhaust some of the air from the bell-jar by ap- 

 plying the mouth to the rubber tubing, and 

 then replace the clamp. 



i. Is the pressure of air greater now within the 

 bell- jar or without? 



