In the putrefaction of vegetable matter the cellulose is attacked by specific organisms, which have been thoroughly investigated by Omeliansky (75). He has shown that the fermentation of cellulose is an anærobic process, caused by two species of bacteria belonging to the class of butyric ferments. Morphologically the organisms closely resemble one another, but one of them decomposes the cellulose with evolution of hydrogen, the other with evolution of methane; in both cases considerable amounts of acetic acid and normal butyric acid are produced. I have previously stated that monads and infusoria take part in the process of putrefaction, but I do not know that their action has been studied in the same way as that of bacteria. The life history and morphology of some of these monads was studied in 1871 to 1875 by Dallinger and Drysdale (76). These authors, in their researches into the life history of the monads found in a putrefying infusion of cod’s head, came to the conclusion that “bacteria are not the only or even (in the end) the chief organic agents of putrefaction, for most certainly in the later stages of a disintegration of dead organic matter the most active agents are a large variety of flagellate monads.” Dallinger cultivated some of the monads in Cohn’s fluid, and found that they lived and multiplied in it. Their spores were killed at a temperature of 250° F. There is a big field of research open in this direction. The consideration of the chemical aspect of putrefaction is a vast subject, and would demand a special treatise. I shall only call your attention to one or two points of interest. Taking the simpler bodies first, sulphuretted hydrogen is formed in putrefying liquids in two ways: (1) by reduction of the sulphates in the liquid by an anærobic organism Spirillum desulfuricans; (2) by bacteria capable of growing in the presence of oxygen such as B. coli commune and B. lactis ærogenes, which ferment glucoses with formation of lævorotatory lactic acid and evolution of CO_{2} and hydrogen, and if at the same time the material contains albumin or sulphur, H_{2}S is given off; these organisms are incapable of reducing sulphates. Beijerinck (64) has investigated this process, and found a variety of different forms intermediate between the two above-mentioned, but all possessing the same characteristics so far as their chemical action is concerned, so that they may be classed as one order, which he calls Aerobacter. Stich (65) found phosphorus pentoxide in the residue from the putrefaction of casein, nuclein, lecithin, and protagon; and in the putrefaction of certain organs of animals and plants, gases containing phosphorus are evolved. The nucleic acid of yeast yielded phosphoric acid along with hypoxanthin and xanthin.