Hemoptysis ; H&matemesis 195 



into ; /SaAXety, cast), the larger the vessel plugged and the more important 

 the resulting asphyxia. An embolus caught at the forking of an 

 artery does not completely block it, but allows a small quantity of blood 

 to pass beyond it ; this additional fluid coagulates in the capillaries and 

 eventually involves them in a hcemorrhagic infarction (infarcio, stuff- into, 

 in allusion to the engorgement of the tissue with blood). The anatomy 

 of infarction is the same whether it be in the lung, spleen, liver, kidney, 

 heart, coronary artery, or the brain ; but only in the lung can the 

 plug come from a systemic vein, for such, unless it be a very minute 

 one, must lodge in the lung. An embolus in any other viscus may come 

 from a pulmonary vein, from a vegetation detached from a mitral or 

 aortic valve, or from a fragment which has scaled from a diseased 

 artery but not from one of the systemic veins. A patch of liver- 

 tissue may also be damaged by an embolus brought through the portal 

 vein. The infarcted area may slough, or become the seat of abscess, 

 or may quietly undergo decolouration and organisation. Pulmonary 

 infarctions are often associated with haemoptysis. 



Sometimes, on the occurrence of an extensive pulmonary infarct, a 

 murmur which was previously heard on the right side of the heart dis- 

 appears, the vegetation which caused the murmur having been washed 

 off into a branch of the pulmonary artery. 



The pulmonary veins, two from each lung, return the arterial 

 blood by separate openings into the left auricle ; they have no valves. 

 A vein comes from each lobe, and, as the third lobe of the right lung 

 belongs to the upper lobe, so the median pulmonary vein joins the right 

 upper vein. 



In the root of the lung the veins are in front of the pulmonary 

 arteries and of the bronchi. The right veins pass behind the right 

 auricle and the ascending aorta, and the left pass in the root of the 

 lung, in front of the third part of the aortic arch. 



Blood brought up from the lungs is necessarily mixed with air, 

 and is therefore bright-red and frothy ; it is alkaline, and is coughed up 

 (Jicemoptysis, at/xo, blood ; TTTUCO, spit). That issuing from the stomach 

 comes up with retching it is dark, and often is mixed with food and 

 gastric juice ; it is, therefore, acid (hcematemesis e/xeco, vomit). 



When blood which has been coughed up is small in quantity it 

 usually comes from the bronchial capillaries, whilst severe bleeding is 

 usually due to a large artery in the lung having been eroded. But 

 even copious haemorrhages can occur from the bronchial capillaries, 

 just as fierce bleeding may occur from the capillaries of the nose. 



The trachea consists of about sixteen horse-shoe cartilages. (For 

 the anatomy of the trachea see p. 131.) The mucous membrane is 

 covered with columnar ciliated epithelium, and contains in its depths 

 mucous glands and lymphoid tissue. 



The bronchi resemble the trachea in structure, but the smaller ones 

 are not flat behind, the hore-shoe cartilages becoming complete circles. 



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