A Textbook of Practical Physiology

Book Preface

The term “physiology” is derived from a Greek root with a Latin equivalent “physiologia”, originally meaning “natural knowledge” (Physic- = nature; -logy = study of). Though first used by Jean Fernel, a French physician, in 1542, the word “physiology” did not come into common use till the 19th century. The subject of “physiology” now refers to the origin, development and progression of living organisms—from bacterias to vertebrates to trees. Thus, there are many branches of physiology. However, we are primarily concerned with “Human Physiology”, i.e. the functional characteristics of the human body.
It is said that medicine is as old as man, and the growth of our knowledge of physiology is closely linked to the growth of medicine— the mother of all branches of natural science. Chemistry, physics, botany, zoology, pathology, pharmacology, microbiology and their branches have all evolved from the study of the art of healing. And they have, in turn, contributed tremendously to the advancement of medical science. Man is always in search of new and better means of maintenance of health and cure of diseases. This has resulted in new lines of thought and newer methods of investigations from time to time, thus creating new sciences.
It is interesting to note that many of the outstanding physiologists have been well known physicians. We are now aware of the tremendous body of physiological knowledge that has its origin in the study of disease. In turn, the exciting progress in physiology during the last two centuries has greatly enriched our knowledge of disease and put medicine on a scientific footing. The student must, therefore, never lose sight of the fact that the knowledge he/she gains from physiology will form the solid basis of all branches of medicine that he/she will be studying later— pharmacology, pathology, internal medicine, surgery, gynecology, etc.

Over a century ago, William Osler, the famous physician said, “The study of physiology (and pathology) within the past half century has done more to emancipate medicine from the routine and thralldom of authority than all the work of all the physicians from the days of Hippocrates to Jenner, and we are as yet on the threshold.”