A process of configuring a web-fed printer is disclosed. An electrical property of the cell culture is measured as a control signal, and a parameter of a stimulus is adjusted in real time to maintain the control signal at a specified value as the environment of the cell culture is altered, for example, pharmacologically. A positioning rib for restricting the relay terminal is provided on a bottom portion of the second recess portion of the cover body. 5 pH units about the pK value of the soluble, buffering species.