Production of three-group metaphases in the bone-marrow of the golden hamster

A FEW years ago, a new type of chemically produced abnormality of mitosis, henceforth termed ‘three-group metaphase’, appearing shortly after an injection of hydroquinone, in the intestinal germinativo cells of the mouse, was reported in Nature1. Later, the rat also proved itself to be a convenient material, while the guinea pig, the chick and chick fibroblast cultures were not responsive as regards this effect2.