[16] A. Fraenkel has recently reported histological investigations in which he could demonstrate in one case true myelocytes in inflamed lymph glands. He says (xv. _Congress f. innere Medecin_): "For some time past I have had systematic examinations carried out by my assistant, Dr Japha, on the granulations of the leucocytes contained in these glands in a large number of infectious diseases, which are accompanied by acute swelling of the lymphatic glands, such as scarlet fever, diphtheria, typhoid. They were performed in the following way: dry cover-slip preparations were made from the juice of the glands removed shortly after death, and were stained in the usual way by Ehrlich's triacid mixture. Amongst a large number of cases thus examined, it was possible in only one case of scarlet fever--but in this beyond all doubt--to demonstrate the presence of mononuclear cells with neutrophil granulation." The extreme rarity of this condition supports our opinion that the formation of neutrophil mononuclear elements cannot be regarded as a normal function of the lymphatic glands. Polynuclear neutrophil cells are nearly always naturally present in inflamed lymph glands, as a product of the inflammation which has immigrated there. Every pus preparation shews that the polynuclear neutrophil leucocytes can change in the tissues to mononuclear, and the isolated observations of Japha should be explained in this manner. [17] Moreover the investigations of Roietzky are quite without foundation, inasmuch as the tibia of the dog, upon which this author performed his experiments, contains in all races of dogs--according to the information very kindly given us by Prof. Schuetz--no red marrow, but fatty marrow only, which as is well known is incapable of the smallest haematopoietic function. [18] We draw particular attention to the small number of eosinophil cells, since according to Ehrlich's postulates this absence of eosinophil cells is incompatible with the diagnosis of a leukaemia. [19] In contrast to this lymphatic metamorphosis of the bone-marrow, in myelogenous leukaemia a myeloid transformation of the other blood-forming organs, especially of the lymph glands is found; a transformation sufficiently characterised as myeloid by the presence of myelocytes, eosinophils, and nucleated red blood corpuscles. III. ON THE DEMONSTRATION OF THE CELL-GRANULES, AND THEIR SIGNIFICANCE. During the last ten years a large amount of valuable work has been done on the cell-granules from histological, biological and clinical sides. This has particularly assisted haematology, where a number of problems remain whose solution is only possible by the aid of a knowledge of the granules. We must therefore consider the history, methods, and results of this work.