124 ANATOMY AND PHYSIOLOGY. 



inside of the chest is inflamed, it is called pleurisy or pleuritis, and 

 is denoted by the sharp cutting pain which is felt when we draw a 

 breath. If uncombined with pleuritis, the pain in pneumonia 

 (inflammation of the lungs) is not great. It is rather tightness of 

 the chest, and oppression of the breathing, that are felt. These 

 are caused by the difficulty the air finds in getting admission into 

 the condensed air-vesicles. From the same cause, pneumonia is 

 generally attended by rapid heaving and breathing. As the quan- 

 tity of air that can be brought into contact with the blood is dimin- 

 ished, fuller and more frequent inspirations require to be made. If 

 the hepatization extends to the whole of one lung, then there can 

 be no motion of the chest on that side, as the air enters only to 

 other lung. These signs are of special importance in children. 

 Whenever the breathing of a previously healthy child becomes 

 rapid and heaving, alarm should be felt for its safety. 



The branches of the windpipe have another coat below the inner 

 or mucous one, which, like that of the intestines, is muscular, and 

 can, it is thought, contract and diminish their size. This contrac- 

 tion is supposed to be the cause of the sudden difficulty in breath^ 

 ing, so often felt by asthmatic persons. In asthma, however, other 

 causes combine to produce this difficulty; for, 1st, there is generally 

 more or less habitual inflammation of the larger air-tubes ; and, 

 2dly, from the repeated violent fits of coughing, the air-vesicles 

 become distended or ruptured, so that the cavity of the chest is per- 

 manently filled to a considerable extent with these distended vesi- 

 cles (bullce). The surface of the lungs of old asthmatic persons 

 may be seen studded with these, like little bladders, sometimes as 

 large as walnuts. 



The only other disease of the lungs we shall notice, is the almost 

 invariably fatal one, consumption (phthisis pulmonalis). This dis- 

 ease consists in the formation, in the lungs, of a peculiar substance 

 called tubercle. Tubercles are at first small semi-transparent 

 bodies, like pins'-heads ; but as they increase in size and number, 

 they unite, and form masses generally like yellowish cheese, occa- 

 sionally as large as a walnut or an orange. At a later period, this 

 cheesy matter becomes softened, and is coughed up, leaving cavities 

 in the lungs more or less extensive, under the irritation of which 

 the patient sinks. Consumption, from very accurate calculations, 

 is known to cause about one in every four deaths in England and 

 North America, so that some knowledge of the causes which produce 

 it, is important to almost every one. From extensive statistical 



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