LUNGS 



3537 



LUNGWORT 



chest cavity, divides into a right and left 

 bronchus. Each bronchus enters a lung, where 

 it divides and subdivides into countless minute 

 tubes, the smallest of which open into cup- 

 shaped depressions known as air sacs. Each of 

 these has upon its inner surface a close net- 

 work of blood tubes called capillaries. The air 

 sacs are arranged in groups known as lobules, 

 and the lobules are united into lobes. There 

 are two lobes in the smaller left lung, and three 

 in the right. 



The bronchial tubes and blood vessels, to- 

 gether with lymphatics and nerves, with which 

 the lungs are also supplied, are all bound to- 

 gether by elastic tissue ; the lungs can therefore 

 stretch like rubber bags when filled with air. 

 In proportion to their size they are the lightest 

 organs of the body, weighing in man about 

 three and one-half pounds and in woman about 

 two and three-fourths pounds. The lungs of a 

 baby are pinkish, those of an adult slate-col- 

 ored and mottled, and those of an elderly per- 

 son of a still darker tint. The change in color 

 is more pronounced in the lungs of city dwell- 

 ers, who live in a smoky and dusty atmosphere, 

 than of those who breathe the pure air of the 

 country. 



The Work of the Lungs. It is by means of 

 the lungs that the body cells are kept supplied 

 with oxygen. As the blood circulates through 

 the body, carrying nourishment to its tissues, 

 it gives up oxygen and absorbs impurities, and 

 must be sent to some central supply station to 

 be renewed. The lungs constitute this supply 

 station. With each intaking of the breath a 

 quantity of fresh air containing oxygen is car- 

 ried to the lungs, and the oxygen, seeping 

 through the thin walls of the air sacs and of the 

 capillaries embedded in them, is absorbed by 

 the blood, to be carried to all parts of the 

 body, while the waste material (carbon diox- 

 ide) is expelled as the air is breathed out again. 

 The process of taking air into the lungs is 

 known as inspiration, and that of expelling it 

 as expiration. In the ordinary breathing of an 

 adult about eighteen inspirations and expira- 

 tions occur every minute, night and day. The 

 extent of lung surface exposed to the air is sur- 

 prisingly large ; if trie walls of the air sacs could 

 be spread out flat and placed side by side they 

 would cover an area of 2,600 square feet. It 

 has been estimated that about twenty-five 

 ounces of oxygen are taken into the body each 

 day. A detailed description of the processes of 

 inspiration and expiration may be found under 

 the heading BREATH AND BREATHING. 

 222 



Diseases and Care of the Lungs. The most 

 dangerous of the diseases peculiar to the lungs 

 are pneumonia and consumption. Both are in- 

 fectious diseases and both are most prevalent 

 among those who live in crowded, insanitary 

 quarters and are forced to breathe foul air. 

 Pneumonia is inflammation of the air cells in 

 the lungs; inflammation of the bronchial tubes 

 is known as bronchitis; and pleurisy is the 

 name given to inflammation of the pleura, the 

 thin, elastic membrane that covers the outside 

 of the lungs. The importance of having public 

 halls, schools and homes well supplied with 

 fresh air is more and more being emphasized 

 as the weakening effect of bad air on the lungs 

 and on the entire system is becoming generally 

 recognized (see HEATING AND VENTILATION). It 

 is also important that the lungs have ample 

 space in which to expand and contract. The 

 practice of wearing clothing that restricts the 

 movements of the ribs and abdomen in the 

 breathing process, and habits that make one 

 stooped and round-shouldered, cannot be too 

 strongly condemned. 



Alcoholic beverages and cigarettes should be 

 avoided by anyone who wishes to have a strong, 

 healthy pair of lungs. Alcohol tends to diiate 

 the blood vessels and to thicken the walls of 

 the air sacs, decreasing the supply of oxygen 

 and interfering with the interchange of oxygen 

 and carbon dioxide. Habitual users of alcohol 

 are especially susceptible to pneumonia. Cigar- 

 ette smokers, in order to secure the full enjoy- 

 ment of the weed, usually draw the smoke into 

 the lungs, and the poisonous nicotine is ab- 

 sorbed by those organs. S.C.B. 



Consult Janeway's Respiration. 



Related Subjects. The reader is referred to 

 the following articles in these volumes : 

 Asphyxiation Heart 



Breath and Breathing Pleurisy 

 Bronchitis Pneumonia 



Circulation of the Blood Pulmotor 

 Drowning Tuberculosis 



LUNGWORT, lung' wurt, a perennial herb of 

 the Mertensia family, named in honor of Franz 

 Mertens, a German botanist. It is known also 

 as Virginia cowslip and bluebell, and is a favor- 

 ite early spring flower- from Southern Canada 

 to South Carolina and west to Nebraska. The 

 flowers are trumpet-shaped, pink in the bud, 

 but afterward purplish-blue, and hang in loose 

 clusters at the end of a smooth, leafy stem. 

 The leaves are large and at first are rich dark 

 purple, later becoming bluish-gray. When ma- 

 ture the flower has four seedlike nuts of a 

 leathery appearance. 



