narrowed in the subregion 9 in which the elastomer compound 2 is arranged when a pressure force is exerted and the valve is therefore actuated the elastomer compound 2 needs to expand only slightly into the first recess 4 in order to fully close the flow channel 4 u2032 in order to actuate the valve a smaller pressure force is therefore required than if the elastomer compound 2 in the relaxed state had been arranged entirely outside the flow channel 4 u2032 by narrowing the flow channel 4 u2032 in the region of the elastomer compound 2 a liquid or a gas would stagnate at this position or its flow speed would increase greatly at this position in order to prevent this as represented in the sectional representation along the line a a u2032 an indentation of the flow channel 4 u2032 as seen from the front side 10 is formed in the support body 1 by virtue of the indentation the cross sectional area of the flow channel 4 u2032 is equal everywhere in the region of the valve so that stagnation or the increase in the flow speed of a liquid or a gas in the region of the elastomer compound 2 or the second recess 3 can be prevented in order for the valve to be usable in biochemical devices the materials which come in contact with the liquids or gases must.