FUNCTION

in physiology, the special activity of a cell, ti ue, or organ. In organisms which comprise but a single cell, all the various types of activity nece ary for the mainten ance of the living state are undertaken by the cell as a whole; the amoeba, for example, performs the proce e s of engulf in g its food, digesting it, excreting waste material and up the nutrient matter into its building own substance by chemical and physical actions in which all parts of the cell to join. Multicel lular organism s, seem on the other hand, po e cells which differentiated for special activities, are and their form is determi ned by the work they are called upon to do. Again, certain cells take on a measure of continuity with each other to form ti ues, are again differentiated accord in g which to the work they have to perform. Thus have connective ti ues, including we the varieties: o eous ti ue, cartilag inous ti ue, fibrous ti ue, adipose ti ue, etc., nervous ti ue, epithelial ti ue, etc. ti ues enter into the structur e of These with special activities; thus we organs say the F. of the stomach is to digest, that of the kidney to excrete waste liquid products, and so on. tities are so related that any change made in one produces a corresponding in the other, then the latter is change said to be a function of the former. This relation is usually represented by_the letters F, f, 0, u, etc. Thus y—F (2), u=f(x), v»=0(z), denote that y, u, » are functions of z, and their values are determined for any particu lar value of z when the form of the function in question is given. z is in this case the independent variable; y, u, ¥ are dependent variables. By taking corresponding values of (say) x and y for co-ordinates, curves may be obtained representing graphically the function concerned.