A device for growing living cells that are not in suspension in a continuous manner, comprising: a flexible tubing containing culture medium and a surface on which the living cells can grow, wherein the tubing is transparent or translucent to measure turbidity; a system of gates (3, 4, 5)achieved by clamps, each capable of open and closed positions wherein the system of gates divides the tubing into: i) an upstream region containing unused culture medium and an unused surface on which said cells can grow; ii) a downstream region containing spent culture medium; and iii) a growth chamber region for growing said cells disposed between the upstream and downstream regions; the system of gates (3,4,5) being constructed and arranged to open and close so as to clamp off and define the growth chamber region of the tubing between the upstream and downstream regions of the tubing, and to cyclically redefine the growth chamber region of the tubing so that a first portion of the previously defined growth chamber region becomes a portion of the downstream region of the tubing, and a portion of the previously defined upstream region of the tubing becomes a portion of the growth chamber region of the tubing and provides the surface for further growth of said cells; and a turbidimeter or other apparatus arranged to measure optical density of the living cells in the culture medium, wherein the closed gates defining the growth chamber region, the gated region of the tubing constituting the growth chamber region, the medium and the culture within the growth chamber region are moveable together through a simultaneous movement of the system of gates (3,4,5) so that each of the gates does not move with respect to the tubing when the gate is in a closed position, and wherein said cells do not grow in suspension. a flexible tubing containing culture medium and a surface on which the living cells can grow, wherein the tubing is transparent or translucent to measure turbidity; a system of gates (3, 4, 5)achieved by clamps, each capable of open and closed positions wherein the system of gates divides the tubing into: i) an upstream region containing unused culture medium and an unused surface on which said cells can grow; ii) a downstream region containing spent culture medium; and iii) a growth chamber region for growing said cells disposed between the upstream and downstream regions; the system of gates (3,4,5) being constructed and arranged to open and close so as to clamp off and define the growth chamber region of the tubing between the upstream and downstream regions of the tubing, and to cyclically redefine the growth chamber region of the tubing so that a first portion of the previously defined growth chamber region becomes a portion of the downstream region of the tubing, and a portion of the previously defined upstream region of the tubing becomes a portion of the growth chamber region of the tubing and provides the surface for further growth of said cells; and i) an upstream region containing unused culture medium and an unused surface on which said cells can grow; ii) a downstream region containing spent culture medium; and iii) a growth chamber region for growing said cells disposed between the upstream and downstream regions; a turbidimeter or other apparatus arranged to measure optical density of the living cells in the culture medium, wherein the closed gates defining the growth chamber region, the gated region of the tubing constituting the growth chamber region, the medium and the culture within the growth chamber region are moveable together through a simultaneous movement of the system of gates (3,4,5) so that each of the gates does not move with respect to the tubing when the gate is in a closed position, and wherein said cells do not grow in suspension.