TRANSACTIONS OF SECTION D. DEPT. ANATOMY AND THYSIOLOGY. 6l 1 



tentive tissue of the aortic valves.* The quantity propelled at each stroke can only 

 have been the difference between what was admitted through the mitral orifice and 

 what regurgitated through the partially patent aortic orifice. Besides this, there 

 must have been the constant backward pressure of arterial elasticity bearino- on the 

 cardiac walls, even during the period of rest in the circulatory cycle. In the third 

 case an impediment was caused to the action of the heart itself by additional friction 

 due to the destruction of its serous covering, and the additional mass of false mem- 

 brane as well as adjacent tissues, which it was thus compelled to keep in movement 

 at every contraction. In the fourth and last case, the only assignable cause for the 

 great enlargement must be the increase of what Dr. Haughton has named the 

 capillary coefficient. It here stands for the resistance, not of the capillary system 

 alone, but of the whole arterial network, from the aorta onwards, which is described 

 as highly rough and atheromatous. In the transparent structures on the surface of 

 the brain this condition could be seen to penetrate even into the smallest vessels, 

 and it may, therefore, be fairly assumed to have been universal. It has been shown 

 by Dr. Bright that disease of the kidneys, unconnected with valvular disease or 

 disease of the aorta, has a tendency to produce enlargement of the heart.. Dr. 

 Peacock proves this statistically by giving the proportion of enlarged hearts as 

 eleven out of eighteen cases examined. The smaller arterioles in cases of renal dis- 

 ease have also been demonstrated by Dr. Johnson to possess a largely increased 

 amount of muscular fibre. Whether the hypertrophy in this ca9e was originally 

 due to this cause, or went backwards to the insufficient renal excretory surface sup- 

 plied by the single healthy kidney, it is difficult to say. Placing the cases in a 

 tabular form : — 



The rate of the first two cases due to aortio lesion is very similar, being nearly 

 an ounce per week ; the third, due to pericardial friction, is about half this amount ; 

 in the last, though the actual weight gained is not far different from that of the' 

 third, the ratio to the normal size of the organ in a boy of 14 is considerably 

 greater, and the hypertrophy in proportion to the muscular development of the 

 patient much more marked. It may be noted that the pregnant uterus increases 

 by about twenty-four ounces in nine months or thirty-six weeks, or two-thirds of 

 an ounce per week, a quantity far less than that shown by the heart. 



* Dr. Haughton writes on this subject :— "The chief resistance in the open con- 

 dition of the valve arose from the vis inertia of the blood column, which had to be 

 set in motion afresh at every heart-stroke.' 





KB 2 



