THE NECESSITY FOR DEEP BREATHING 



between the cells which need oxygen and the air which is 

 taken into the lungs. The products formed when oxygen 

 is used in the body are exhaled in the breath and may be 

 detected by simple tests. 



Experiment. To determine some products of respiration. 



Materials: Glass tubing. Limewater. Test tube. 



Method and Observations: Blow the breath through a large, dry glass 

 tube until there is evidence of material deposited. From its appear- 

 ance what do you judge this to be? Blow the breath through lime- 

 water in a test tube for a short time. What change occurs? Recall 

 the meaning of this test, which was previously shown in Chapter III. 



Conclusion: What are two substances produced in our bodies which 

 escape in our breath? 



The necessity for deep breathing. The blood, too, 

 carries back to the lungs carbon dioxide which has been 

 formed in the cells 

 as a result of the 

 work done there, and 

 this carbon dioxide, 

 as we have seen by 

 our limewater test, 

 is expelled from the 

 lungs during respira- 

 tion. The lungs dur- 

 ing ordinary breath- 

 ing do not expel 

 more than one sev- 

 enth of their total 

 load of air. More 

 of the air in the 



Tidal air is that air taken in and expelled during ordi- 

 nary breathing. Complemental air is what we can 

 take in, in addition to tidal air in a full deep breath. 

 Reserve air is what we can force out in addition to 

 tidal air by forced expiration. Residual air is that 

 which always remains in the lungs. 



air in 



lungs can be expelled when we take a deep breath, but 

 there is always some air left in the lung sacs known as 

 residual air. This air must be very impure, as it lacks 



