72 HUMAN BIOLOGY 



Experiment 19. How the Ribs are Lifted. Make a model like 

 sketch to represent backbone, breastbone, and two ribs, using pins to 

 make joints loose at corners. Use cords for diagonals. 

 What happens when cord ac is pulled? When cord 

 bd is pulled ? The cords correspond to the two sets 

 of muscles between the ribs. 



Experiment 20. Study of Laughing. Place the 

 hands upon the waist and abdomen when laughing. 

 What motion occurs at each sound of laugh ? Draw 

 in the abdominal wall with a jerk. What is the effect 

 upon the breath ? 



Experiment 21. Modifications of the Breath. 

 Write I, E, or IE after each word in this list, accord- 

 ing as inspiration, expiration, or both, are involved in the action. (Test 

 with sham acts if possible.) Sighing, sobbing, crying (of a child), 

 coughing, laughing, yawning, sneezing, hiccoughing, snoring. 



Experiment 22. Effects of Exercise. Count and record the rates of 

 breathing before and after vigorous exercise. 



Experiment 23. Comparative Study. Observe and record the rate 

 and manner of breathing of cow, horse, dog, cat, etc. Is the air drawn 

 in or sent out more quickly? Is there a pause? If so, after which stage 

 of breathing? 



Experiment 24. Emergency Drill. Resuscitation from drowning, 

 etc. See Coleman's "Elements of Physiology," page 356. 



Necessity for Breathing and for Specialized Organs of 

 Breathing. The body is a self -regulating machine which 

 possesses energy. This energy, like that of steam engines, 

 arises from oxidation which takes place continually, but at 

 a varying rate. Food for fuel is taken at intervals, but 

 oxygen must be taken in continually. Man breathes about 

 eighteen times per minute. The blood in the tissues soon 

 becomes dark because of loss of oxygen and absorption of 

 carbon dioxid. It is then pumped through the heart to 

 the organ which has the function of absorbing oxygen 

 and giving off carbon dioxid (Fig. 67). In some animals, 

 as the ameba and the earthworm, the surface of the body 

 suffices for breathing. This cell breathing is the true 

 essential respiration ; it is universal among living things, 



