[27] It is also of interest to notice the behaviour of the eosinophil cells in the passive form of leucocytosis, lymphaemia. _A priori_ both conditions could be combined. As C. S. Engel has established in the congenital syphilis of children a simultaneous marked increase of lymphocytes and eosinophil cells is found. The lymphocytosis in these cases is probably due to the anatomical changes of the lymph glands, and the eosinophilia to specific chemiotactic attraction. [28] In his monograph on Bothriocephalus anaemia Schauman, with reference to the behaviour of the eosinophil cells, states that he has found them in but few cases of this disease. [29] This view has lately received striking confirmation from the interesting experiment of Baeumer, who produced on himself by means of continued stimulation with _Urticaria ureus_ a considerable increase in four days of the mast cells in the irritated portions of the skin. [30] That a well-marked basophil leucocytosis has not so far been observed may be thus explained. The substances which attract the mast cells are very rarely produced in the body; much more seldom than the corresponding substances attractive for the eosinophils. In morbid conditions, where substances attracting the mast cells were present, it might be possible to find a suppuration of mast cells, or a mast cell leucocytosis as well. In this connection an observation of Albert Neisser is of the greatest interest. He met with (private communication) one, out of numberless cases of gonorrhoea, in which the purulent secretion consisted entirely of mast cells. [31] Unger has recently published completely analogous observations on the human breast for the mast cells. Under the influence of stagnation of the milk he saw an invasion of the gland tissue by typical mast cells. [32] A very interesting observation of Goldmann's deserves mention here. Goldmann found in preparations of the pancreas of proteus sanguineus, containing parasites, that the eosinophil cells in the neighbourhood of the encapsuled parasites were much increased, whereas they were sought for in vain, in more distant parts. [33] A case observed some time back by Ehrlich may here be mentioned as a characteristic example. A woman received a blow in the region of the spleen by a fall from the roof, which gradually led to a marked splenic enlargement. As no other symptoms appeared, the surgeon in charge proposed splenectomy, on the assumption of a pure splenic leukaemia. Examination of the blood, however, shewed a condition fully corresponding with myelogenic leukaemia, and thus prevented surgical interference. [34] Ehrlich was once able to recognise, by balancing the different forms of cells, the blood preparations after the loss of their labels from some ten cases of leukaemia. [35] Literature given by A. Fraenkel. V. DIMINUTION OF THE WHITE BLOOD CORPUSCLES (LEUKOPENIA).