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XXXIII. On the Cause of the Circulation of the Blood. By 

 John William Draper, M.D., Professor of Chemistry in 

 the University qf New York, 



\ MONO physiological problems there is none of greater 

 ■*■*- interest, or of more importance in its relations to the 

 well-being of man, than that which proposes to determine the 

 true cause of the circulation of the blood, and the various 

 other liquids which pass from one portion of living systems to 

 another. Unquestionably one of the most important disco- 

 veries ever made by any physician was that of the route of 

 the circulation by Harvey. The clearness with which he and 

 his successors developed that doctrine not only fully established 

 his views, but gave rise to a serious error which is scarcely 

 removed in our times. 



That error relates to the action of the heart. These earlier 

 writers regarded the circulation of the blood as a hydraulic 

 phasnomenon, supposing that the heart simulated exactly the 

 action of a pumping machine. It is now on all hands con- 

 ceded that this organ discharges a very subsidiary duty. The 

 whole vegetable creation, in which circulatory movements of 

 liquids are actively carried on without any such central me- 

 chanism of impulsion ; the numberless existing acardiac beings 

 belonging to the animal world ; the accomplishment of the 

 systemic circulation of fishes without a heart; and the occur- 

 rence in the highest tribes, as in man, of special circulations 

 which are isolated from the greater one, have all served to 

 demonstrate to physiologists that they must look to other 

 principles for the cause of these remarkable movements. 



When we reflect how large a portion of the human family 

 is destroyed by diseases dependent on derangements of the 

 circulation, and to how great an extent the practice of medi- 

 cine, as a scientific pursuit, must depend on just views of this 

 important function, a natural philosopher can scarcely be more 

 profitably employed than in attempting a solution of this pro- 

 blem. 



I am persuaded that the phenomenon may be accounted 

 for upon physical principles in a satisfactory manner ; that 

 we can co-ordinate together, and arrange as examples of one 

 common law, the various forms of circulatory movements, 

 whether they occur among vegetables or animals, among in- 

 sects, or fishes, or mammals ; and that the facts which we 

 meet in derangements of these motions, or their cessation, as 

 in fainting, coughing, and the different forms of disease, or 

 such as take place after hanging, the inhalation of protoxide 

 of nitrogen, or alcoholic drunkenness, or in that most remark- 



