<p>In a cell block (100), a plurality of cells (10) are housed in a row in a holder (11), the holder (11) has cylindrical housings (11a) for housing the cells (10), a plurality of grooves (20) extending axially are formed on the side wall of the holder (11), and a securing member (30) for securing the cell block (100) is mounted in the grooves (20).</p>
