The original woodcut of these curious parasites is reproduced in Fig. 268, also in Plate IX., No. 7, and which evidently belong to a different species, numbering thirty-nine altogether. Quite recently Mr. G. H. Broadbent, M.R.C.S., Manchester, sent me a supply of these interesting bodies lately discovered by him in an infusion of cow manure. On examining a drop with a power of 1500 diameters they were discovered moving over the field of the microscope with a gyrating motion by the aid of flagella projecting from each corner of the pocket. After some days, having attained their full growth of four, eight or sixteen in a pocket, they break up, and recommence the formative process. Sarcinæ are certainly pathogenic in their nature. Cocci in groups, or asso-cocci, are similarly associated. These several forms of spiro-bacteria are enclosed in a transparent cell-wall, and are sometimes described as zooglæa. Of bacteria the most characteristic groups are bacillus, bacterium, and a species of clostridium, a bottle-shaped bacillus. It is, however, difficult to draw a sharp line between so-called _species_. _Spiro-bacteria_, or _spirilla_, possess short or long filaments, rigid or flexible, and their movements are accordingly rotatory, or in the long axis of the filaments. These bodies are again divided into comma bacilli, or vibrios--a name invented by the older microscopists who first described them--some species of which have a flagellate appendage, to which their movements are due.