The view, that the granules are special metabolic products of the specific cellular activity, is strongly supported by the great chemical differences between them. Ehrlich made these peculiarities clear for the blood-cells, and found that their granulations differ from one another, not only in their colour reactions, but also in their =shape= and =solubility=; so that they must be sharply distinguished. Whilst for instance the majority of the granules are more or less rounded forms, in some classes of animals, _e.g._ in birds, the analogues of the granules of mammalian blood are characterised by a decided crystalline form, and a strong oxyphilia. The substance of the mast cell granulations is also crystalline in some species of animals. The size of the individual granules is constant in any animal species for every kind of granule--excepting only the mast cells. The eosinophil granulation reaches its greatest size in the horse, where really gigantic examples are found. The presence of granulated colourless blood-cells has been demonstrated in the most various classes of animals, and even in the blood of many invertebrates, particularly, as Knoll has shewn, in the Lamellibranchiates, Polychaetes, Pedates, Tunicates and Cephalopods. Concerning vertebrates, especially the higher classes, accurate and ample researches are to hand. In birds we recognise two oxyphil granulations, of which one is embedded in the cells in the crystalline, the other in the usual granular form. Amongst the vertebrates most investigated classes possess granulated polynuclear cells. To this circumstance Hirschfeld has recently devoted a thorough paper containing many details worthy of note. In the majority of the animals observed, he found too that the polynuclear cells contained neutrophil granules; in only one animal, the white mouse, did he find them, or granulations analogous to them, completely wanting. According to the investigations carried out some years back in Ehrlich's laboratory by Dr Franz Mueller, these results of Hirschfeld's must be described as inaccurate. After many vain endeavours, Dr Mueller was able to find a method by which numerous though very minute granules could be found in the polynuclear cells of the mouse. The case shews that it is not permissible to assume the absence of granules, when the ordinary staining methods are not at once successful. There is no universal method for the staining of granules, any more than for the staining of various kinds of bacteria. Indeed all granules, that are easily soluble, vanish when the triacid method is used, and so a homogeneous cell protoplasm is simulated.