Howard cell fruit juice counting chamber and coverslips

The Howard cell is a glass slide 76 mm x 35 mm with a central circular island and is used for counting mould fibres and spores in fruit juices, especially from tomatoes. With the K20 coverglass in place, a 0.1mm thickness of liquid is contained over the central island. The coverglass has 25 calibrated fields of 1.382mm diameter through which to view the particles. This coverglass removes the necessity of precise adjustment of the microscope and eyepiece graticule in the original Howard method.