CHAPTER III 
WILLIAM HARVEY AND EXPERIMENTAL OBSERVA- 
TION 
AFTER the splendid observations of Vesalius, revealing in 
a new light the construction of the human body. Harvey took 
the next general step by introducing experiment to determine 
the use or purpose of the structures that Vesalius had so 
clearly exposed. Thus the work of Harvey was complemental 
to that of Vesalius, and we may safely say that, taken together, 
the work of these two men laid the foundations of the modern 
method of investigating nature. The results they obtained, 
and the influence of their method, are of especial interest to us 
in the present connection, inasmuch as they stand at the 
beginning of biological science after the Renaissance. Al- 
though the observations of both were applied mainly to the 
human body, they served to open the entire field of structural 
studies and of experimental observations on living organisms. 
Many of the experiments of Harvey, notably those relating 
to the movements of the heart, were, of course, conducted 
upon the lower animals, as the frog, the dog, etc. His ex- 
periments on the living human body consisted mainly in 
applying ligatures to the arms and the legs. Nevertheless, 
the results of all his experiments related to the phenomena of 
the circulation in the human body, and were primarily for 
the use of medical men. 
In what sense the observations of the two men were com- 
plemental will be better understood when we remember that 
there are two aspects in which living organisms should 
always be considered in biological studies; first, the struc- 
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