RESPIRATION. 39 



Describe the rhythm of respiration. 



The respiratory act is rhythmical, inspiration being slightly mere 

 rapid than expiration, a slight pause occurring after expiration 

 before a fresh breath is drawn. 



Describe the movements of the nostrils and larynx in respira- 

 tion. 



With every inspiration (especially if rapid) there is dilatation of 

 the nostrils and a partial closure during expiration. The rima glot- 

 tidis is in the same way opened for the ingress of air. This is like 

 the respiratory act, in that the opening is a muscular act during 

 inspiration, and the recoil elastic in ordinary breathing. 



What is the composition of the atmosphere ? 

 It has a nearly uniform composition. 



By Volume. By Weight. 



Oxygen, 79 parts. 75 parts. 



Nitrogen, 21 " 25 " 



Carbonic acid, .04. 

 Ammonia and impurities, trace. 



What is the temperature of expired air? 



The expired air is at about the temperature of the body, what- 

 ever its temperature when inspired. 



How much carbonic acid does exhaled air contain? 



While ordinary air contains only about a part of carbonic acid 

 per 1000, expired air is found to contain about 43 parts per 1000 

 of CCL This is varied by conditions of health and disease, age, 

 atmospheric conditions, and a number of other causes. 



How much oxygen is taken from the air in respiration ? 



The oxygen of the exhaled air is decreased in about the same 

 ratio that its carbonic acid is increased (roughly 5 per cent.). This 

 proportion is not exact, as there is some excess of oxygen which is 

 absorbed in the system and does not reappear as C0 2 . 



How much water appears in expired air? 



The amount varies with the atmospheric conditions as well as 

 bodily changes, but ordinarily in a day about 10 ounces of water in 

 the form of vapor are found in expired air in excess of that normally 

 present. This may amount to 30 ounces, or fall as low as 6 

 ounces. 



