24 THE NATURE AND TREATMENT OP 



DESCRIPTION OF THE LUNGS. 



The lungs are known, in common parlance, as the " lights," 

 they may be considered as a double organ, separated from 

 each other by that part of the pleural membrane known as the 

 mediastinum; when distended by air, or inflated, they occupy 

 the whole cavity of the chest, but the moment expiratory 

 action ensues they are in a state of collapse, occupying not 

 more than one-half the volume of the chest. The lungs are 

 composed of arteries, absorbents, veins, and nerves, and rami- 

 fications of the bronchial tubes, known as air cells, connected 

 together by a cellular substance, known as parenchyma. A 

 healthy lung, when immersed in water, will float upon the 

 surface ; yet if the lungs as in the foetal state, have never been 

 inflated, they sink like a stone. 



FUNCTION OF THE LUNGS. 



The principal function of the lungs, is to arterialize, or 

 decarbonize the blood. This arterialization of the circulating 

 fluid is more essential to vital integrity, than either food or water, 

 for animals can live many days, weeks, and even months, 

 without a particle of extraneous food — hybernating animals 

 for example — whereas, no creature having lungs, to expand 

 and contract, can be expected to live more than a few seconds 

 when deprived of the " breath of life." 



The functional acts of respiration and expiration, must 

 necessarily be divided into two parts ; the acts are performed 

 in the ratio of from fourteen to twenty times in a minute, it 

 is more frequent during exercise, and under many states of 

 disease. When an animal is located in a pure atmosphere, 

 and the lungs are in good working order, all the impurities of 

 the blood are brought into the presence of oxygen through the 

 medium of the air cells ; a change in the character and color 

 of the blood is very soon effected which I shall notice. In the 

 first place the venous blood as it appeared before aeration, was 

 of a dark purple approaching a black color ; by union with 

 oxygen respired, it has changed its color for one of scarlet, 



