Human physiology : prepared with special reference to students of medicine / by Joseph Howard Raymond.
- Raymond, Joseph H. (Joseph Howard), 1845-1915
- Date:
- 1901
Licence: Public Domain Mark
Credit: Human physiology : prepared with special reference to students of medicine / by Joseph Howard Raymond. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![HUMAN PHYSIOLOGY. INTRODUCTION. Definitions.—Pliysiology is the mience ichich treats of func- tions. J]y the term fuiictioii is meant the eharaeteristic work performed by an organ. An organ may be defined as a structure which performs a function or functions, for the special or char- acteristic work of an organ may not -be limited to a single function : thus the pancreas secretes not only pancreatic juice, whicii is its external secretion, but also another product, which is its internal secretion {i^. 233). Lifeless things perform no functions, hence physiology has no dealings with inanimate things. Rocks, stones, and other members of the mineral kingdom at no time possess life ; consequently they perform no functions, and with them physiology has no concern : we cannot speak of the physi- ology of minerals. Plants and animals are sometimes living and sometimes dead : when living they perform functions, when dead they perform no functions; in the latter condition they are like the rocks so far as function is concerned, and with them physiology has nothing whatever to do. It is only when they are living that they perform functions, and it is then and only then that with them physiology concerns itself. Another definition which might be given of physiology is, that it is the science ichich treats of vital phenomena. A brief consideration of this definition will bring us to the same conclu- sion as did that of the preceding dcfiniticm. Of life in its essence we know nothing. Metaphysicians have endeavored to ex})laln life, and some have even ventured to point out its seat, but the fact remains that we are utterly ignorant of its nature. We only- know that it exists by certain manifestations which it presents.. AVhen we see a growing plant or a moving animal, we say of each that it is alive. In the higher forms of animals and plants it is. easy, under ordinary circumstances, to determine whether they are living or not; but in the lower forms this determination is some- times a mo.st difficult task. The evidences upon which reliance is placed to determine the presence or the absence of life are spoken of as vital phenomena. Thus, if in examining an animal we find that its heart beats, we .say that the animal is alive; but](https://iiif.wellcomecollection.org/image/b21209893_0021.jp2/full/800%2C/0/default.jpg)
