Know Thyself 31 



mechanism: heart, arteries, veins, valves and so on.* 

 These were known long before his time. What he did 

 was to prove how these are interrelated, how they 

 operate together and depend upon one another, how, 

 for example, the work of the heart is supplemented by 

 the muscularity of the arterial walls, and how the 

 valves of the veins aid the veins in returning the sys- 

 temic blood to the heart. Hitherto anatomy and 

 physiology had been largely sciences of the members 

 of the body. With this discovery they were started on 

 their way as sciences of the systems of our members. 



Discovery after discovery closely dependent upon 

 that made by Harvey soon followed, revealing still fur- 

 ther the nature and interdependence of the body parts. 

 Only one group of these need detain us now. The dem- 

 onstration of that interrelationship between the blood 

 and nervous systems which constitutes the vaso-motor 

 system, and which opened the way for our present in- 

 sight into the so-called organic sensations and our 

 physico-psychic conception of the emotions, must be 

 counted as one of the greatest of the progeny of Har- 



* Modern historical inquiries into the discovery of the circulation 

 make it certain, as Luigi Luciani points out (Human Physiology, 

 trans, by F. A. Welby), that Harvey's predecessors, notably Ces- 

 alpinus and Sarpi, came much nearer a clear understanding of 

 the operations of the heart and blood vessels than Harvey's writ- 

 ings take cognizance of. The history of the discovery is highly 

 interesting both scientifically and from the standpoint of the psy- 

 chology of discovery; but the question of due credit to the various 

 investigators who contributed to the final result does not affect the 

 argument of this essay. 



