This, the lowliest form of animal life, consists of a mass of contractile substance with a nucleus.

Many authors have described the Amoeba coli as of constant occurrence in epidemic dysentery. It is present in the stools and in the lesion in the intestine. It is also found in the lesions of the liver, met with as secondary results in dysentery. According to Osier there is not in dysentery a suppurative inflammation such as results from the action of pyogenic microbes, but a progressive cedematous condition and necrosis of the tissue, along with proliferation of the fixed cells of the tissues. In the liver also, unless there is an addition of pyogenic agents, there is no proper suppuration, few multinuclear leucocytes being present, but rather a necrosis of the liver tissue. The amoeba has been observed in epidemics in several countries, in Egypt by Kartulis, in Russia by Losch, and in America by Councilman, Lafieur, and Osier.