minute beings. The supposition that one variety of bacteria can produce lactic acid, another butyric acid, a third caproic acid, has recently been stigmatized as "superstition"; but it was forgotten that the cells of the hog's liver produce a different acid from that obtained from the liver of a goose, ox, or man a fact which evidently is of the same order as that given for the bacteria.
Another point deserves our special attention—the, inner organization of the single cells, and the organisms composed of them. Since our present means are insufficient to distinguish this with certainty, we consider the cell or living protoplasm as being without structure. This reasoning is untenable, as it is only supported by the imperfection of our apparatus and methods; on the contrary, other weighty facts are in favor of the presence of such an organization. Above all, it is to be emphasized that within each living cell a number of chemical processes are constantly taking place simultaneously, all of which are necessary for the existence and vitality of the cell. These processes are of so different a nature that it is difficult to believe that they take place within a perfectly homogeneous mass. It seems much more simple and natural to suppose that each of the reactions takes place separately, which could be most readily effected by an internal organization of the cell. The peculiar figures which have been noticed in the division of the cells also speak in favor of this, as do the differences in their exterior forms, which are always governed by the inner organization; the variations in the further development, and particularly the effect on the surroundings, are also in favor of this view. How can we perceive that the bacteria of ordinary putrefaction are comparatively harmless, while the bacteria of splenitis are so destructive, unless we seek the cause in the peculiar inner structure?
Hence the chemical processes within the living cell are of two kinds: those in which ferments take part, and those in which they do not. The ferments are definite chemical compounds, which are able to decompose large quantities of other substances without undergoing any apparent change themselves. The manner in which this takes place is not yet explained, but we have reasons for comparing these processes with others in which a small quantity of one body, e. g., sulphuric acid, gradually converts a large quantity of another, e. g., alcohol, into ether and water. In this case the sulphuric acid acts like a ferment on the alcohol, and the similarity is so striking that it has been attempted to explain both in the same way. Formerly it was supposed that the simple contact of one body with another was in many cases sufficient for complete decomposition, and contact action, produced by the so-called catalytic force, was spoken of. Later it was found that in the above example the sulphuric acid first combines with the alcohol to form ethyl sulphuric acid, which is afterward decomposed with a fresh quantity of alcohol into ether and sulphuric acid. Accordingly, the action of every ferment must be considered as consist-
