Ribs 

 Raised Lowered 



Diaphragm 

 Lowered Raised 



Inspiration 



Expiration 



BREATHING MOVEMENTS IN MAN 



When the diaphragm, the muscular partition between the thorax and the abdomen, 

 is pulled down, the chest cavity enlarges. When the ribs are raised, the chest also 

 expands, and air comes in through the windpipe. The rib muscles and the diaphragm 

 normally work in unison. When these muscles relax, the chest cavity contracts and 

 forces out the air in the lungs 



This taking on or putting ofT of oxygen seems to depend upon the relative 

 quantity of oxygen, and is a "reversible" reaction, as shown in this equation: 



Hemoglobin + oxygen T^ oxyhemoglobin 



When blood reaches tissues far from the oxygen supply, the reaction moves 

 to the left. In the vicinity of the lung (or other respiratory organ) the 

 change moves to the right. When the blood contains much oxyhemo- 

 globin, it is bright red; M^hen little, a maroon color. 



A man row^ing in a race or climbing a mountain may use about one and 

 one-fourth gallons of oxygen per minute. If he had no red blood corpuscles, 

 it would be necessary to circulate 375 gallons of fluid each minute to supply 

 this amount of oxygen.^ 



^Actually, there is but about one and a half gallons of blood in the body. At this rate 

 all the blood would have to rush round the body 250 times a minute, or about four times 

 each second. Obviously, no human heart could sustain such a load. One gallon of blood with 

 hemoglobin carries as much oxygen as 60 gallons would without it. It takes about 300 gallons 

 of water at body temperature to dissolve one gallon of oxygen. 



206 



