. Laboratory work in bacteriology. Bacteriology. 448 BACTERIOLOGY. Moreover, the buried organism, owing to the filtering power of the soil, is not to be considered as a source of danger, especially if surrounded by dry earth. Method of analysis.—The collection of samples of earth from various depths can be readily accomplished by means of Praenkel's earth-borer. For each culture experiment a definite quantity of the soil should be weighed out, or a measured volume taken. The latter is the simpler proce- dure, and can be done with a small platinum spoon which has a capacity of A Fig. 59.
. Laboratory work in bacteriology. Bacteriology. 448 BACTERIOLOGY. Moreover, the buried organism, owing to the filtering power of the soil, is not to be considered as a source of danger, especially if surrounded by dry earth. Method of analysis.—The collection of samples of earth from various depths can be readily accomplished by means of Praenkel's earth-borer. For each culture experiment a definite quantity of the soil should be weighed out, or a measured volume taken. The latter is the simpler proce- dure, and can be done with a small platinum spoon which has a capacity of A Fig. 59. Esraarch's apparatus for counting colonies in roll-tubes. >- With the above sterile instrument one spoonful of the earth is transferred to a tube of liquid gelatin. The con- tents of the tube are then mixed thoroughly, with a steril- ized platinum wire, and an Esmarch roll-tube is made. The soil and the organisms present are thus brought into per- fect contact with the gelatin, and after a lapse of a few days colonies develop. The colonies can be readily counted, either direct, or by the aid of an Esmarch roll-tube counter. This apparatus is shown in Fig. 59. The roll-tube is placed in the holder andjthe average number of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Novy, Frederick George, 1864- . Ann Arbor [Mich. ] G. Wahr
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