A method for generating stimulus response curves shows how the phenotype of one or more cells change in response to varying levels of the stimulus. At least one actuating button that can be pressed downwards is arranged on the upper side of the outside housing. To prevent the shelf 16 from swinging outwardly, the tabs 64 overlap and are retained behind the fingers 68. That is, changes that do not affect the structure of content within a web document are allowed, while changes that affect the structure of the content are not allowed. A run-off conduit is operated by means of a further flowthrough valve disposed close to the nozzle.