2 THE TONER LECTURES. 



practice of medicine can fail to appreciate how very prevalent 

 the latter are, and the question is worthy of the deepest study, 

 What causes them, and can we by any means materially lessen 

 their increasing frequency? Again, is there anything in our 

 habits and mode of life, in our work, our amusements, which 

 can be so altered as to avert them ? Of many we know the 

 origin to be either an inherited trouble, or an attack of acute 

 rheumatism, or those changes in the muscular structure and 

 in the coats of the great vessels, which go hand in hand 

 with general decay. But these sources of cardiac disease 

 are so well understood that nothing would be here gained by 

 their description. I desire rather to speak to you of a cause 

 very little appreciated, to some scarcely known — the produc- 

 tion of disease of the heart by strain and over-action. Strain 

 and over-action may go together, or they may not, and the 

 former may or may not precede the latter. While thus there 

 is a close connection, at times nearly an identity, between the 

 two, it will be convenient, in a general way, to limit the idea 

 of strain, unless the contrary is stated, to an acute strain, an 

 injury by sudden, violent effort; and to think of over-action, 

 over-exertion, or over-work — for these terms may be employed 

 almost sj-nonymonslj'' — as a persistent excitement and derange- 

 ment produced by less rapidly acting causes. 



Now, a strain may rupture the muscular walls of the heart, 

 and though there is the greatest doubt whether it can do so 

 miless they are previously diseased, there is none as regards 

 the rupture under strain of fatty or otherwise enfeebled walls. 

 But I pass this by to speak of breaks and tears in the valvular 

 apparatus and great vessels, clearly the result of sudden disturb- 

 ance. A person, for instance, is seized quickly, after unusual 

 exertion, with pain in the heart. He is recognized to have a 

 distinct mui-mur, which never leaves him, and sooner or later 

 the typical phenomena of valvular disease will show them- 

 selves, varying, of course, as this or that valve has been the 



