178 Disease of the Heart 



narrowed, for then the left auricle is always over-full, and when it allows 

 regurgitation from the ventricle. Cough also is a sign of valvular dis- 

 ease, because the irregular passage of blood through the lungs worries 

 the pneumogastric filaments. 



The lungs and the right auricle being distended, the inferior vena 

 cava is over-full and dilated, the liver becomes large and tender, and 

 ' nutmeg' engorgement (p. 337) is produced. Later on, albuminuria, 

 and dropsy of the peritoneum, pleura, and pericardium, and oedema 

 of the legs, occur. The superior cava is also overloaded, and thus 

 cedema of eyelids, headache, and apoplexy are accounted for, as is also 

 the capillary congestion which gives rise to clubbing of the fingers. 

 The kidneys and spleen are also engorged and the urine is albuminous. 

 The albuminuria is the result of nephritis, for heart-disease causes 

 nephritis just as it does bronchitis ; but, the kidney being so much more 

 distant from the heart than the lungs, the student is apt to overlook 

 this pathological sequence. 



The structure of an artery. The innermost coat consists of a 

 layer of flat endothelium upon a bed of elastic fibres and connective 

 tissue (intiina). Next come alternating layers of circular elastic and 

 non-striated muscular fibres (media), and outside these more elastic and 

 connective-tissue fibres (adventitia). The internal and middle coats 

 break clean through and retract when a ligature is tightly applied, the 

 external, tough coat being puckered up. Inflammation is set up by 

 the operation, and the clot which forms becomes glued to the wall, 

 and in time nourished by the vasa vasorum and duly organised. The 

 narrow zone of artery which is girt by the ligature necroses, and is set 

 free by linear ulceration in the adjoining tissue, the fibrinous plug being 

 a safeguard against haemorrhage. 



An artery is usually enclosed in a fibrous sheath, often with a vein 

 or with venae comites ; this sheath has to be opened up before the 

 ligature is applied. If the artery be too freely denuded in the opera- 

 tion, the vasa vasorum are needlessly destroyed and the vessel runs a 

 risk of sloughing. 



A large artery, and especially so the aorta, has the middle coat 

 greatly thickened by elastic fibres, so that it may yield as the blood is 

 pumped into it, and then, when the semilunar valve is closed, may 

 exert continuous pressure upon the blood, forcing it onwards. 



THE ARCH OF THE AORTA 



The arch of the aorta springs from base of the left ventricle at the 

 level of the sternal end of the third left intercostal space. 



The first part of the arch ascends obliquely forwards to the second 

 right costal cartilage. 



l\cl<itions.\\. is within the pericardium, and has /// front the |>ul- 

 artery, which comes from the anterior ventricle, and the 





