necessary for each separate organism, paying due attention to other nutritious materials and conditions, will no doubt lead to exact methods for the culture of separate cells in the laboratory. Following this line of inquiry we could surround certain microorganisms with peptones whose composition we are familiar with, and so acquire a deeper insight into the processes of their metabolism.[1] Even the mode of decomposition of the substrate, and of the intermediate stages, may furnish some important hints as to the specific functions of the cell and, in many cases, allow us to recognize particular organisms.[2] We shall, by this means, understand why certain germs thrive upon certain media, while on any other substrate they either cease to grow or perish entirely.
It will also be possible to determine exactly, which of the decomposites and by-products formed from the culture medium produce harmful effects.
There is no doubt that, in the organic world, certain species prepare the soil for others, and in this way one organism acts as a pioneer to the others. It is a most interesting task to follow up this co-operation of different living beings in all its details. To a certain degree we have, in the co-operation of single
