BIOLOGY IN HUMAN AFFAIRS 



The heart is hidden away in the chest. All of its functions 

 and the changes which it undergoes must be determined 

 from evidence secured indirectly. It is possible by thumping 

 the chest to outline roughly the borders of the heart and 

 thus to know whether it is larger or smaller than it ought 

 to be. By use of the X-ray the borders of the heart may be 

 outlined exactly. It is possible, by listening to the heart, 

 to determine whether or not the valves are functioning 

 satisfactorily and to know whether it is likely that they 

 are constricted — thus permitting an insufficient amount of 

 blood to pass through — or are dilated — permitting blood 

 to leak back after it has passed through. When such changes 

 occur, characteristic murmurs arise which can be heard 

 by means of a stethoscope. 



It is possible, by listening to the beat of the heart and 

 by feeling the pulse, to tell whether or not the beat is 

 taking place satisfactorily, and whether or not the blood 

 is being pushed through the blood vessels and back to the 

 heart as it ought to be. Such measurements are, however, 

 loose determinations. A device called the electrocardio- 

 graph measures, by photographing waves on a photo- 

 graphic plate, the changes in the beat and any disturbance 

 of the mechanism of propelling the heart beat through 

 the organ itself. Such methods are far more accurate than 

 the use of the unaided human senses. 



One may feel the pulse in the wrist with the finger, or 

 one may attach to the wrist a device called the sphygmo- 

 graph, which records the variations in a pulse beat on a 

 moving strip of paper in such a way that the various 

 changes may be determined. The machine is far superior 

 to the human finger in detecting changes. 



There was a time when it would have been considered 

 equivalent to murder to push a needle into the sacs around 

 the heart. To-day the physician frequently extracts the 

 fluid accumulated in that sac, on the basis of his studies 



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