WILLIAM TOWNSEND PORTER 99 



the making of experiments that shall answer the proposed 

 question Yes or No. Let me illustrate this by one or two 

 examples. A young investigator was recently given this 

 problem : The effect of changes in the blood-supply of 

 the heart muscle upon the rate and force of the heart-beat. 

 He was furnished with a method by which the quantity of 

 blood which flows through the walls of the heart - - that is 

 to say, through the heart muscle itself could be accu- 

 rately measured and varied at will. The animal was anes- 

 thetized with ether, and while still under the influence of 

 the ether was bled. The heart was removed from the dead 

 animal and was kept beating with the defibrinated blood 

 of the same animal. It was discovered that the rate of 

 the pulse, that is the number of heart-beats per minute, 

 might remain almost unchanged in spite of wide varia- 

 tions in the quantity of food supplied to the heart muscle ; 

 but the force of the beat was found to vary directly with 

 the food supplied. The bearing of this investigation upon 

 practical medicine must be obvious to every one. 



The arteries which feed the substance of the heart are 

 frequently diseased. Their walls may become so thickened 

 that the blood may have great difficulty in reaching the 

 muscle-cells of which the heart is composed. Then the 

 ill-fed organ cannot do its work, and may suddenly give 

 out. Heart starvation is a frequent cause of sudden death. 

 In the course of the investigation just mentioned it was 

 observed that the heart received a significant supply of 

 blood through the vessels discovered by Thebesius in 1708. 

 No one had supposed that these minute channels, which 

 pass from the cavities of the heart into its walls, had any 

 part in the nutrition of the organ ; the nutrition of the 

 heart was thought to be the exclusive function of the car- 

 diac arteries. This new idea was the starting-point of an- 

 other investigation. It was found that the heart might be 

 kept beating for hours while its arteries were empty, pro- 



