340 PA THOGENIC BA CTERIA. growth in bouillon and in peptone solutions is accompa- nied by the production of indol. The spirillum is pathogenic for mice, guinea-pigs, and canary birds. Spirillum Weibeli.—This spirillum (Fig. 95) was found in 1892 by Weibel in spring-water which had a long time FIG. 95.—Spirillum Weibeli, from agar-agar; x 1000 (Itzerott and Niemann). before been infected by cholera. It is short, rather thick, and distinctly bent, often forming S-shaped figures. The colonies before liquefaction sets in are described as pale-brown, transparent, circular, and homogeneous. Liquefaction is much more rapid than in cholera, and causes the borders of the colonies to become irregular. In the centre of each colony a little depression is ob- served. In gelatin puncture-cultures the growth is rapid, be- ginning first upon the surface, where a large flat, saucer- shaped liquefaction, extending to the sides of the tube, forms. Scarcely any growth takes place in the puncture, but the superficial liquefaction, separated by a horizontal line from the normal gelatin, descends slowly. Upon agar-agar a grayish-white layer is formed. No growth has been obtained upon potato.