MUSCLES. 483 



If a muscle has been much distended, it does not contract 

 readily at first. This we notice in the case of the urinary bladder : 

 when the urine has been retained too long it stops, after flowing 

 for a short time ; and flows again when the bladder has a little 

 recovered itself. Leeuwenhoek believed that over-distension of 

 the heart might cause sudden death : and he probably was right, for 

 sometimes nothing is seen in cases of sudden death but extreme 

 distension of the right half of the heart, and Professor Coleman, 

 after hanging and drowning animals, found the right auricle and 

 ventricle turgid with blood, and the auricle insusceptible of irri- 

 tation ; but, on opening one of its veins and allowing blood to 

 escape, the application of stimulus in a few minutes induced con- 

 traction of the auricle.P Pressure upon a muscle facilitates its 

 action. Thus the over-distended bladder, and the uterus after 

 delivery, contract better if the hand is placed over them ; and a 

 moderate ligature is often employed by those who are about to 

 make much exertion with particular muscles. 



When a muscle is weakened by excessive action, a peculiar 

 unpleasant sensation is experienced, termed fatigue. The weaker 

 the system, the sooner is this sensation experienced. General 

 weakness at the commencement of disease is usually attended 

 by this sensation of weariness, though, when disease is over and 

 mere weakness remains, it is commonly not felt till exertion is 

 made. Distress of mind will bring on this sensation. When a 

 set of muscles is much more exercised than usual, they at first 

 become stiff and painful : but these conditions soon cease, not- 

 withstanding equal exercise is persevered with. 



All muscles increase by use ; so that, if a man has spent much 

 of his life in some mechanical occupation which requires the 

 action of particular muscles, these are easily distinguished through 

 their disproportionate magnitude. It is thought that the mus- 

 cular fibres of the urinary bladder increase by exercise more than 

 any others ; a continued obstruction to the exit of the urine calls 

 them into such exertion that the inner surface of this organ often 

 resembles that of a cardiac cavity. The heart also frequently 

 grows inordinately from obstruction to the exit of its blood. But 

 this organ, above all other muscular parts, will grow inordinately 

 from mere morbid disposition. In the heart this hypertrophy 

 may produce much distress, if any undue excitement occurs ; 



p Lectures on the Blood, by James Wilson, F.R.S. London, 1819. 

 K K 3 



