PHYSIOLOGY IN THE STUDY OF DISEASE 87 



But in many cases the blood is dammed back in 

 the lungs, and the heart gets over-distended and 

 cannot drive it on to carry the oxygen to the body. 

 In such a condition the veins are distended with 

 blood, and bleeding by opening one of them relieves 

 the pressure on the heart and enables it to drive 

 the blood onward. This has been found useful 

 in many cases, even although it decreases the 

 amount of oxygen-carrying blood. 



Thus you see that a study of the physiology is 

 alone sufficient to elucidate the real nature of the 

 condition, to tell what is wrong and why it is 

 wrong, and to suggest the appropriate line of 

 treatment. 



Of course the further question of whether it is 

 possible to render these poisonous gases innocuous 

 had to be tackled. The chemist was called in. It 

 had been found that charcoal has a peculiar action 

 in absorbing and holding on to these gases. It 

 was argued that if air containing these poisonous 

 gases were made to pass through a layer of charcoal, 

 it should be possible to breathe it with safety. 



Physiologists, when investigating breathing, had 

 devised methods to enable people and animals to 

 breathe through valves, so as to separate the out- 

 going from the ingoing air, and these valves had 

 been applied to masks to be worn by those engaged 

 in life-saving operations after colliery explosions 

 to secure them a supply of oxygen. It was thus 



