Of great theoretical interest is the contrast between eosinophil and neutrophil cells. At the height of ordinary leucocytosis, the number of eosinophil cells is diminished often to disappearance; whilst during its decline they occur in abnormally high numbers. Hence it follows that the eosinophil and neutrophil cells must react towards stimulating substances completely differently, and in a certain sense oppositely[27].
It seems, generally speaking, that the bacterial =metabolic products formed in human diseases which are positively chemiotactic for the polynuclear neutrophil cells are negatively chemiotactic= for the eosinophils, and _vice versâ_.
The explanation of the individual clinical forms of leucocytosis is self-evident from the above description. The occurrence of physiological and inflammatory leucocytosis is exclusively to be explained by chemiotaxis. In the other forms, however, other factors also come into play, in particular the increased activity of the bone-marrow, or the extensive transformation of fatty to red marrow, causing a large fresh formation of leucocytes.
[alpha] 2. ~Polynuclear eosinophil leucocytosis. Mast cells.~
Our knowledge of eosinophil leucocytosis is still of comparatively recent date. After Ehrlich demonstrated the constant increase of the eosinophil cells in leukæmia a considerable time elapsed before an eosinophilia was found in other diseases, an eosinophilia however that differs in its essential traits from the leukæmic type. To Friedrich Müller we owe the first researches in this direction, at whose suggestion Gollasch investigated the blood of persons suffering from asthma; in which he was able to demonstrate a considerable increase of the eosinophil cells. This was followed by the researches of H. F. Müller and Rieder, who discovered the frequency of eosinophilia in children, and its presence in chronic splenic tumours; further by the well-known work of Ed. Neusser, who observed a quite astounding increase of the oxyphil elements in pemphigus, and by the almost simultaneous analogous observations of Canon in chronic skin diseases. From amongst the flood of further papers upon this condition we will only mention the comprehensive account of the subject by Zappert.