The question, what cells produce on their destruction actively chemiotactic substances, is of very great importance; but cannot be answered with the material at present available. The breaking up of ordinary pus cells or lymphocytes does not appear to give rise to any such substances; but there is much evidence that the decomposition products of epithelial and epithelioid cells act chemiotactically. Thus we can explain the frequent occurrence of eosinophilia in all kinds of skin-diseases. Again, in all atrophic conditions of the gastric, intestinal and bronchial mucous membrane there occurs a local accumulation of eosinophil cells; further, this kind of cell is increased in the neighbourhood of carcinoma. Additional support for this view is seen in the fact that in bronchitis and asthma the less the suppurative element of the secretion is developed, the more numerous are the eosinophil cells. An observation of Jadassohn is worthy of mention in this connection. He observed abundant eosinophil cells in foci of lupus after injection of tuberculin. In these foci then, by the destruction of the epithelioid cells brought about by the tuberculin, substances must have been produced which act chemiotactically on the eosinophil cells. The specific substances are absorbed and reach the blood, and impart to it also the chemiotactic power. =The direct cause then of most forms of eosinophilia seems actually to lie in a destruction of tissue, and in the products thus produced.= On the other hand, it cannot be doubted that substances foreign to the organism, circulating in the body, may act chemiotactically on the eosinophil cells[32]. The observations quoted above, of the well-marked eosinophilia in the different forms of Helminthiasis, may here be specially mentioned. The action of the Helminthides was formerly regarded as purely local, but the indications that they act also by the production of poisonous substances continue to increase. Thus Linstow has pointed out that the general typhoid state, and the fatty degeneration of liver and kidneys, that is of organs which the Trichina does not reach, necessitate the assumption of a poisonous substance. And in several varieties of Ankylostoma as well, there is distinct evidence of the production of a poison. We gather from Husemann's article on "animal poisons" (Eulenberg's _Realenencyclopoedie_ 1867) that just as Ankylostomum in man produces the well-known severe anaemia, so Ankylostomum trigonocephalum in the dog, and Ankylostomum perniciosum in the tiger, causes analogous general effects. Bothriocephalus latus too is now generally accredited with the production of a definite toxic substance; and the common tapeworm even, by no means infrequently brings about injuries to the body which are to be referred to the action of a poison.