AND PHYSIOLOGY. 



255 



451. Inspirations compared with Pulsations — Quan- 

 tity of Watery Vapor Given off in Twenty-four Hours- 

 Amount of Carbonie Acid Exhaled — The Amount of Solid 

 Carbon given off. — If we compare the number of inspira- 

 tions in a minute with the pulsations of the heart, we shall 

 find the proportion of the former to the latter is as one to 

 four or five in the human adult. Every fifth breath is usually 

 deeper than the preceding four, and the time occupied by 

 each respiratory act is about three and a half seconds ; and 

 all the blood in the body (when in vigorous exercise) probably 

 is exposed to the air in the lungs every two minutes. 



The quantity of watery vapor which is ordinarily exhaled 

 from the lungs in twenty-four hours ranges from sixteen to 

 twenty ounces. The amount of carbonic acid, however, varies 

 much more, being from one to three pounds in twenty-four 

 hours, and the causes of variation are temperature, age, sex, 

 state of health or disease, development of the body, muscular 

 exertion or repose, sleep or watchfulness, and period of the 

 day. " This gas (carbonic acid) contains in every 100 pounds 

 28 pounds of carbon (charcoal) and 72 pounds of oxygen 

 (gas). Hence the weight of carbon which escapes in this 

 form from the lungs of a full-grown man varies from five to 

 fifteen ounces in twenty- four hours." 



452. Respiration as a Source of Animal Meat. — The 

 value of the function of breathing as a means of pro'ducing 

 animal heat, will be considered under the organs for produc- 

 ing heat. 



453. Changes in the Food effected by Respiration. — 

 A third object of breathing is to effect such changes in the 

 food that it can be directly converted into the different tissues 

 of the body. Hence the oxygen of the air is a part of the 

 food that we live upon. For although the gluten which is so 



451. Wha* is the relative number of inspirations and pulsations of the heart? What 

 length of time is occupied in breathing? What quantity of vapor of water is exhaled in 

 twenty-four hours, and what amount of carbonic acid? How is this amount modified ? 

 What weight of carbon or charcoal is given out of the body by the luns?s everyday? 

 453. W T hat effect has the oxygen of the air upon the glutinous portion of our food ? 



