Blood

The ×400 fields are drawn to scale from two pictures of a stained blood smear, painted for this site to look like photomicrographs: they are not photographs of a real smear. The cells in and round each counting square are the cells of the pictures, and enlarging the view shows the pictures themselves, so the counts are made on them, not invented. The rest of each field is filled with drawn cells at the same density, and some white blood cells are copied in from the pictures so that each field holds a few. A real smear differs from field to field and from person to person.

The red blood cells carrying oxygen, the white blood cells meeting bacteria and the cut that clots are models, not to scale: these happen inside the body, and a smear cannot show them.