IOO THE APEX-BEAT. THE CARDIOGRAM. 



closure (insufficiency) of the valves. The latter causes resistance to the blood- 

 flow by permitting regurgitation of a portion of the blood already propelled 

 onward. In this way there results: 



1. Hypertrophy of the left ventricle from hindrances to the blood-flow in 

 the territory of the greater circulation, chiefly in the arteries and capillaries, 

 not in the veins. In this category belongs stenosis of the aortic orifice and of the 

 aorta further on; also calcification and loss of elasticity in the large arteries, 

 irregular dilatations of the arterial walls (aneurysm) ; insufficiency of the aortic 

 valves, as a result of which the left ventricle is continually subject to the aortic 

 pressure; finally, affections of the kidney, in consequence of which a greater 

 arterial pressure is required in order that the urine may be excreted. In the 

 presence of mitral regurgitation also, hypertrophy of the left ventricle is necessary 

 for compensation, and a similar enlargement occurs in the left auricle in conse- 

 quence of the heightened pressure in the lesser circulation. 



2. Hypertrophy of the left auricle results from mitral stenosis and from 

 mitral regurgitation, and also consecutively to aortic regurgitation because the 

 auricle must overcome the uninterrupted aortic pressure that is present in the 

 left ventricle. 



3. Hypertrophy of the right ventricle results from (a) hindrances to the 

 blood-flow in the territory of the lesser circulation. These are : (a) atrophy of vascu- 

 lar areas of considerable size in the lungs in consequence of destruction, contrac- 

 tion or compression of the lungs and from loss of numerous capillaries in 

 emphysematous lungs. (/?) Overdistention of the lesser circulation with blood in 

 consequence of stenosis of the mitral orifice or of insufficiency of the mitral valve ; 

 also consecutively to hypertrophy of the left auricle resulting from aortic regur- 

 gitation. (b) Hypertrophy of the right ventricle must occur also in conjunction 

 with insufficiency of the pulmonary valves, which permits the blood to regurgi- 

 tate into the ventricle, so that the pressure of the pulmonary artery prevails 

 continually in the cavity. This condition is exceedingly rare. 



4. Hypertrophy of the right auricle develops consecutively to the condition 

 last mentioned, likewise in association with stenosis of the right auriculo-ventricu- 

 lar orifice, or from insufficiency of the tricuspid valve. This condition is un- 

 common. When several obstructions in the circulation occur together there is 

 a combination of the resulting phenomena. O. Rosenbach has investigated the 

 manner and method by which the heart maintains its activity after the occur- 

 rence of valvular lesions. If the aortic valves were perforated, with or without 

 simultaneous injury to the mitral and tricuspid valves, the heart performed first 

 an increase of work, which counteracted the physical defects, so that the blood- 

 pressure did not fall. The heart, therefore, possesses reserve powers, which are 

 brought into play only when they are required. In consequence of the valvular 

 insufficiency dilatation first develops as a result of the regurgitation of blood into 

 the affected chamber of the heart. Then follows hypertrophy, but until this is 

 completed the compensation must be effected by the reserve power. 



Under the conditions that especially render diastole difficult there should yet 

 be mentioned : large effusions into the pericardial sac or pressure on the heart from 

 tumors. The systole is greatly interfered with by adhesions between the heart 

 and the connective tissue of the mediastinum. Under such circumstances the 

 surrounding tissues, even the thoracic wall, must be drawn upon with each con- 

 traction of the heart, so that systolic retraction and diastolic projection occur 

 in the situation of the apex-beat. 



THE APEX-BEAT. THE CARDIOGRAM. 



By the term apex-beat (ictus s. impulsus cordis) is understood the 

 visible and palpable elevation of a circumscribed area of the fifth (less 

 commonly the fourth) left intercostal space, caused by the action of the 

 heart. At times the apex-beat is less distinct, especially when the 

 heart strikes against the fifth rib itself. Changes in the position of 

 the body alter somewhat the situation and the force of the apex-beat. 

 A graphic representation of this movement can be obtained by means of 

 a registering apparatus the apex-beat tracing or the cardiogram. 



Method. To obtain a tracing of the apex-beat the cardiograph of Marey may 

 be.employed. ,The iitstrume,nt has beentmodified by various investigators. The 





