470 MODERN DEVELOPMENTS OF HARVEY's WORK. 



intestinal vessels there is a special provision made for preventing tlieir 

 contraction from causing- too great a rise of arterial pressure. This 

 consists in the depressor nerve, which passes from the heart and tends 

 to produce dilatation of the abdominal vessels, and thus prevent any 

 undue piessure occurring within the heart from their excessive con- 

 traction. 



In the case of the muscles, we have no such nerve. Its jdace seems 

 to be taken by tlie dilating fibers which occur in the motor nerves. As 

 I have already said, liowever, this effect of ddatation in the nuiscular 

 vessels may be at first more than counteracted by mechanical compres- 

 sion at tlie commencement of exertion, and thus the blood pressure in 

 the arteries, and tiie resistance which it opposes to the contraction and 

 emptying of the ventricle, may be unduly increased. 



As a general rule the distention of any hollow muscular organ is 

 attended with great i)aiu. How great is the suflering when obstruction 

 of the bowel in-events evacuation of its contents; or when a calculus, 

 in its passage down the gall duct or ureter, forcibly distends their wall. 

 One of the severest tortures of the Middle Ages was to distend the 

 stomach with water, and the Kmperin- Tiberius could imagine no more 

 awful punishment for those whom he hated than to make them drink 

 wine, and at the same time, by means of a ligature, to prevent the dis- 

 tended bladder from emptying itself The heart is no exce]»tion to tliis 

 rule, and distension of its cavities brings on most acute physical suf- 

 feiing. Its inability to empty itself is a question of relative and not 

 of absolute power; for a strong heart may be unable to work only 

 against enormously increased resistance in the peripheral arterioles, 

 while the heart, weakened by degeneration, may be unable to empty 

 itself in face of pressure little, if at all, above the normal. 



When the contractile power of the heart is not, as it is in health, 

 considerably in excess of the resistance opposed to it in vessels, but 

 only nearly equal to it, a slight increase in the resistance nuiy greatly 

 interfere with the power of the heart to empty itself, and bring on pain 

 varying in amount from slight uneasiness to the most intense agony in 

 angina ])ectoris. This is indeed what we find for a heart whose nutri- 

 tion has been weakened by disease of the arteries, and consequent 

 imperfect supply of blood to the cardiac nuiscle is unalde to meet any 

 increased resistance if this should be ottered to it, and pain is at once 

 felt. In such cases, unless they be far advanced, we find precisely as 

 we might expect, that walking on the level usually causes no pain, but 

 the attempt to ascend even a slight rise, by which the muscles are 

 brought into more active exertion, brings on pain at once. Yet here 

 again we find, as we should expect, that if the patient is able to con- 

 tinue walking t-he pain passes ott" and does not return. These phe- 

 nomena Avouldbe inexplicable were it not for Ludwig's observations on 

 circulation through the muscles, but in the light of these observations 

 everything is made perfectly intelligible. Walking on the flat, by 



