TRANSACTIONS OF SECTION D. — DEPT. ANATOMY AND PHYSIOLOGY. 609 

 Solving this for h, 



h 



_ Q 



Ax*" 



I 



Substituting for Q the product of capacity and rate of pulse, and for the capillary 

 resistance, its value found tor the horse, we obtain — 



/* = ^A. 7 _ 5 = 9-923 feet. 

 39-3 



There is a fourth element to be considered in estimating the heart's work, namely, 

 the friction of the machine itself. This, in a state of health, is kept at its minimum 

 by the beautiful contrivance of the smooth lubricated serous membrane of the 

 pericardium. It will be seen that in disease this condition may be completely 

 altered. 



It appears from Dr. Haughton's calculations, resulting from comparison of 

 several observations, that the average weight of the heart may be taken as 

 = 9-39 ozs. 



Dr. Peacock's laborious collection of weights, both in health and disease,* gives 

 a value not far distant from this : namely, " in persons from twenty to fifty-five years 

 of age it is, in males, 9 ozs. 8 drachins, and in females 8 ozs. 13 drachms." But in 

 disease this is entirely changed. The heart possesses a power of increasing its 

 muscidar force in proportion to any extra work that may be thrown upon it. In 

 extreme cases the hypertrophy thus caused may be very considerable. Even without 

 valvular disease of the organ a remarkable increase may occur, especially in persons 

 whose occupation subjects them to sudden muscular strain, accompanied by forcible 

 holding of the breath, as in the case of paviours working with their rammers. Dr. 

 Peacock records a case in which the heart weighed 40 ozs. 12 drachms, though 

 nothing, except some atheromatous change, was detected sufficient to explain the 

 hypertrophy. In this instance, however, no note was apparently obtained by which 

 the time during which the compensatory process had been going on coidd be 

 ascertained. 



The object of the present paper is to record briefly some cases in which one only 

 of the above-named causes of increased strain was at work ; and thus, by coupling 

 together increase of weight with a fairly accurate statement of the time which 

 had been occupied, to obtain an estimate of the rate at which the hypertrophic pro- 

 cess proceeds in each instance. 



These cases are four in number— 



1. Two of valvular disease of the aortic valve, arising from injury, without any 

 concomitant blood-disease (No. 2). 



2. One of adherent pericardium, dating from a known commencement, unac- 

 companied by valvular or blood-disease, and showing the hypertrophy due to simple 

 increase of friction in the propelling machine (No. 4). 



3. One of congenital or very old atrophy of one kidney, increasing (3) the resist- 

 ance offered by the capillary circulation, without valvular or pericardial disorder. 



Case 1. — A robust man, aged 30, was kicked by a horse on the front of the 

 chest. The animal lashed out with both hind legs at once, and landed a hoof fairly 

 on either side of the sternum. This occurred on October 2nd, 1875. The man im- 

 mediately began to suffer from short breath and other signs of valvular disease of the 

 heart. In spite of this he managed to keep at his occupation of groom until February 

 2nd, 1876. On the 27th of the same month he died. On the following day the heart 

 was found to measure transversely 8^ inches, and in circumference 14 inches while 

 in situ. It weighed-29 ounces. The aorta was laid open in front and the condition 

 of its valves examined. On allowing a stream of water to run into the vessel, there 

 was free flow into the ventricle. On looking into the valves from above, a tri- 

 angular aperture was seen between the flaps, which appeared to be formed in the 

 following manner. The posterior and the right anterior segment acted well, and 

 were in contact along a great part of their adjacent borders. The left anterior seg- 

 ment, however, scarcely acted at all, its free border being widely separated from the 



* ' On the Weight and Dimensions of the Heart in Health and Disease.' 

 1878. r r 



