314: DISEASES OF THE HEART. 



Disorders of the greater (aortic) circulation, which give lise to 

 hypertrophy of the left ventricle, are more rare. This is due to the 

 fact that, in its vast system of vessels, the obliteration of a very great 

 number of capillaries, and even the ligation and compression of the 

 great vascular trunks, is compensated for by dilatation of the vessels 

 of other regions. The impediment to the aortic circulation which 

 most commonly embarrasses the action of the left side of the heart, and 

 to which most cases of hypertrophy of the left side are commonly due 

 (when they are not the result of disease of the aortic valves), is a de- 

 generation of the arterial walls, generally known as " atheroma in its 

 widest sense," and which we shall by-and-by describe in detail as 

 endarteritis deformans. In this affection, which is often widely dif- 

 fused throughout the wall of the arteries, the vessels not only become 

 elongated and tortuous, so that the friction of the blood against the 

 sides of the arteries is increased, but the elasticity of the arterial tunics 

 (a most important auxiliary element of the circulation) is seriously 

 diminished. In the obliteration of the aorta, which sometimes occurs 

 close below the point of entrance of the ductus botalli (see Section HI., 

 Chapter IV.), the left ventricle is also found in a state of considerable 

 hypertrophy. Occupations which require violent muscular exertion 

 have likewise been enumerated among the causes of this disease. If 

 this be true, such hypertrophy also belongs in this category. The 

 n umber and size of the efferent vessels of the aorta are reduced by the 

 pressure to which the capillaries within the contracted muscles are 

 subjected, and thus the contents of the aorta and the tension of its 

 coats are increased. Traube has shown by experiment, that an aug- 

 mentation of pressure takes place in the aortic system during general 

 contraction of the muscles. Traiibe finally counts the hypertrophies 

 usually found ori the left side of the heart, which (even according to 

 Bright) often complicate the third stage of Brightfs disease, as among 

 those which proceed from disturbance of the aortic circulation. He 

 supposes that an increase of tension within the aorta arises, partly 

 from atrophy of the vessels, partly from abnormal fulness of the aorta, 

 from which a reduced amount of liquid is withdrawn into the kidneys, 

 which, by augmenting the obstacles to the evacuation of the left ven- 

 tricle, give rise to hypertrophy. Bamberger brings forward serious 

 objections to this explanation. He shows that the hypertrophy begins 

 in the earlier stages of Brighfs disease, that it does not affect the left 

 heart alone, but often involves the whole organ ; that we sometimes 

 find the aorta not only undilated, but even narrowed, that it is im- 

 probable, and that there is no precedent for the supposition that the 

 destruction of a few renal capillaries should produce a hypertrophy of 

 the heart, to wluch the ligation of large arterial trunks cannot give rise. 



