348 THE ANIMALS AND MAN 



there is an increased rapidity of tissue respiration. During 

 exercise also, the heart responds with a quickened beat and 

 the blood is carried more rapidly to the lungs. All this 

 quickens the movements of the respiratory apparatus so 

 that ventilation of the lungs may be more immediate and 

 complete. 



This shows that the circulatory apparatus and the res- 

 piratory apparatus must work together. Deep breathing 

 would be of no avail were the heart not ready to respond by 

 a vigorous beat. When we run too hard, we get "out of 

 breath." This really means that the heart has become 

 fatigued, that it has been pushed beyond its normal capacity. 



Exercise must therefore not be excessive, but it must 

 be vigorous and regular so as to keep the heart in training 

 for the demands upon it. 



Effects of tight clothing on respiration. Anything that 

 binds the walls of the thorax restricts the movements of the 

 respiratory muscles, the muscles of the ribs and diaphragm. 

 The result is that certain lobes of the lungs fail to enlarge 

 and hence remain unventilated. It is said that more than 

 sixty per cent of the beginnings of lung troubles are found in 

 the unused portions of the lungs. 



Suffocation and artificial respiration. Suffocation re- 

 sults from depriving the lungs of oxygen. This may be 

 brought about by poisonous gases in the air, by obstruction 

 of the windpipe, or by drowning. Death may be prevented 

 in cases of suffocation if artificial respiration is resorted to 

 immediately. In artificial respiration the chest is expanded 

 and contracted artificially so as to induce an inflow of air 

 into the lungs. Three methods have been suggested. 

 In the first method the subject is placed face downwards 

 and pressure is exerted upon the back, then the body is 

 rolled from this to a lateral position. The second method 

 is to place the patient upon his back; then raise the arms 

 above the head and body, and bring them down against the 



