Also in slope and puncture cultures on the various solid media much variation results from the amount of material on the inoculation needle and just how the puncture is made, or the needle drawn over the slope. These variations are largely prevented by the use of standard media and by inoculating by standard methods. The Laboratory Committee of the American Public Health Association has proposed standard methods for all culture media and tests and for methods of inoculation, and these have been generally adopted in this country for comparative work.
Likewise the Society of American Bacteriologists has at different times (1904, 1914, 1917) adopted “descriptive charts” for detailing all the characteristics of a given organism. A committee is at present working on a revision
of the 1917 chart to be presented at the 1920 meeting. One of the earlier charts which includes a glossary of descriptive terms is [inserted in this chapter].
Among the cultural appearances the following are of most importance:
Fig. 144.—Broth cultures × ⅔. 1 uninoculated transparent broth; 2, broth cloudy from growth of organisms; 3, broth slightly cloudy with a deposit in bottom; 4, broth slightly cloudy with a heavy membrane at the surface.
Fig. 145.—A filiform stab or puncture culture. × ⅗.
Fig. 146.—A beaded stab or puncture culture. × ½.