of the host, which seriously affect the metabolism of the latter. It is certainly not necessary in every case that the poisonous substance, the so-called toxin, should originate in the cell of the micro-organism itself; it is just as likely that it is formed, outside the cell, by ferments given off by the latter. When we introduce substances out of harmony with the species or the plasma, we have similarly to reckon with the presence of stages of decomposition, which may be disharmonious with the organism, and capable of producing injurious effects. In this case the disharmonious substrate is the cause of the appearance of a substance, that is disharmonious both in structure and configuration. In cases of invasion by bacteria, we have, on the contrary, a destruction of generally harmonious substances, yet the decomposition is brought about by ferments which are probably of a different kind. The cause of the appearance of disharmonious decomposites is thus to be explained, not by the substrate, but by the nature of the ferments. It is possible that, in time, we may succeed in tracking down in the organism these ferment-like agents that are given off by parasites. For the time being we must be satisfied with being able to point to the possibility of a decomposition of this kind being a cause of injury.
Disharmonious cells may also act injuriously upon the organism, owing to their decomposition inside the
