Y 



X 



60 HUMAN PHYSIOLOGY. 



feet, weighing 18 oz. To obtain this quantity, 300 cubic feet of air are 

 necessary. 



The quantity of carbonic acid exhaled in 24 hours varies greatly. It 

 can be estimated in the same way. Assuming that an individual exhales 

 93 ~h cubic inch at each respiration, in one hour there are eliminated 1008 

 cubic inches, and in 24 hours 24,192 cubic inches or 14 cubic feet, contain- 

 ing 7 ozs. of pure carbon. 



As oxygen and carbon unite to form an equal volume of carbonic acid 

 gas, there disappears daily in the body one cubic foot of oxygen, which 

 in all probability unites with the surplus hydrogen of the food to form 

 water. 



The exhalation of carbonic acid is increased by muscular exercise; 

 nitrogenous food ; tea, coffee and rice ; age, and by muscular development ; 

 decreased by a lowering of temperature ; repose ; gin and brandy, and a 

 dry condition of the air. 



Condition of the Gases in the Blood. 



Oxygen is absorbed from the lungs into the arterial blood by the coloring 

 matter, hemoglobin, with which it exists in a state of loose combination, 

 and is disengaged during the process of nutrition. 



Carbonic acid, arising in the tissues, is absorbed into the blood, in conse- 

 quence of its alkalinity ; where it exists in a state of simple solution and 

 also in a state of feeble combination with the carbonates, soda and potassa, 

 forming the bicarbonates ; it is liberated by pneumic acid in the pulmonary 

 tissue. 



Nitrogen is simply held in solution in the plasma. 



The amount of watery vapor thrown off from the lungs daily is about 

 one pound, with which is mingled organic matter and ammonia. 



Changes in the Blood during Respiration. 



As the blood passes through the lungs it is changed in color, from 

 the dark purple hue of venous blood to the bright scarlet of arterial 

 blood. 



The heterogeneous composition of venous blood is exchanged for the 

 uniform composition of the arterial. 



It gains oxygen and loses carbonic acid. 



Its coagulability is increased. Temperature is diminished. 



Asphyxia. If the supply of oxygen to the lungs be diminished and 

 the carbonic acid retained in the blood, the normal respiratory movements 

 cease, the condition of asphyxia ensues, which soon terminates in death. 



The phenomena of asphyxia are, violent spasmodic action of the respi- 



