Oxford Companion to the Body:
Physiology is defined by dictionaries as ‘the science of the normal functions and phenomena of living things’. The physiology of animals emerged in Europe out of the Renaissance nterest in the experimental method, as exemplified by the work of William Harvey (doctor to Charles I). Harvey's book of 1628 on the Motion of the Heart, ‘Exercitationes Anatomicae de Motu Cordis’, brilliantly analyses structural and functional observations (quantitative as well as qualitative), which remorselessly led him, and similarly lead the present day reader, to the conclusion that the blood circulates, in man as well as in other animals. This volume remains central to our current understanding of the word ‘physiology’ because of its emphasis on experiment, data analysis, and hypothesis testing. Harvey's work also exemplifies the natural symbiois between physiology (‘function’

and anatomy (‘structure’

, a science from which physiology was to emerge as a separate discipline in the second half of the nineteenth century. Harvey's book also connects physiology to medicine. Understanding of every disease follows from combining knowledge of the relevant normal physiology to the way in which it is perturbed in the particular disorder (‘pathophysiology’

.
Historically, the subsequent meaning of ‘physiology’ is well illustrated by the way in which the word is used in the two following quotations. The first is from 1704 (J. Harris, Lexicon Technica): ‘Physiology, is by some also accounted a Part of Physick’ (i.e. Medicine), ‘that teaches the Constitution of the Body so far as it is sound, or in its Natural State; and endeavours to find Reasons for its Functions and Operations, by the Help of Anatomy and Natural Philosophy’. The second (a definition of Charles Darwin's colleague T. H. Huxley), 150 years later, is virtually identical to current usage: ‘whereas that part of biological science which deals with form and structure is called Morphology; that which concerns itself with function is Physiology’.
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