The Microscope. 327 



more pronounced, until one sees a cylindrical cell with a dark spot 

 in each end, and a comparatively large white central area. By very 

 careful examination, however, an exceedingly delicate film, seen in 

 optical section as two tine border lines, can be made out as a lining 

 of the cell-wall throughout the white area. Sometimes the dark- 

 end spots appear like circular dots, but usually conform to the exter- 

 nal shape of the cell, and are concave on their inner sides, or on 

 those looking towards each other. These spots grow gradually smal- 

 ler but do not wholly disappear, at least in many cases, until the cell- 

 wall dissolves, and leaves an oblong free spore entirely colorless, 

 except, perhaps, at the ends, where the violet stain still leaves its 

 mark. When still older, this agent does not color the spores. Ani- 

 line red, with carbolic acid, does stain them. The Bacillus averages 

 ,7// in transverse diameter, but varies from about . 5 ,« to 1 /i . The 

 joints are short, but run from 1 to 3// in length, 1.5, a being more 

 common. When, as pairs, newly divided, the segments are oval, but 

 usually the shape is short, cylindrical. As the spores form, the sides 

 become convex, so that the outline is elliptical, the ends, however, 

 remaining obtuse, or semi-circular. During the period of active 

 growth, the organisms have flagellate motions, but these are never 

 very rapid compared with many others, neither does the power seem 

 to be long retained. 



On plate cultures, the characteristic growth is white, or pearl- 

 like, with peculiarly lobed and fixnbriated margins. Gelatine is not 

 liquified. In liquids, in the incubator as described, a pellicle forms 

 upon the surface within twenty-four hours, but afterward becomes 

 thicker. It is white, or nearly so, usually polished or glazed above, 

 with characteristic granules and pits. The growth extends upward 

 on the sides of the test-tube about three millimeters. After a time 

 the pellicle becomes brittle, easily breaks up and gradually settles to 

 the bottom as a floculent precipitate. 



AVhen some of the culture- fluid, filled with the microbes is 

 smeared upon the upper or under surface of healthy leaves of broom- 

 corn or sorghum,, after forty-eight hours, minute red specks can be 

 seen by the unaided eye. These specks are usually thickly dotted 

 over the entire area to which the application was made; but, some- 

 times when the fluid settles more upon a given portion of the leaf, 

 the spots are conspicuously more abundant there. By the aid of 

 suitable magnification, it can be readily determined that the minute 

 red specks owe their location to the stomates or breathing pores of 



