. Pathological technique; a practical manual for workers in pathological histology and bacteriology. tion of a second sterileblood-serum tube, next touched to the infected surface of the FIG. 19—Method of holding tubes dur-ing inoculation. 218 PATHOLOGICAL TECHNIQUE. first tube, and the wire thus infected gently and thoroughlyrubbed over the surface of the second. In a similar mannera third tube is then infected from the second, and then all thetubes placed in the incubator for eighteen to twenty-four is evident that comparatively few bacteria will be sown onthe medium of the second t
. Pathological technique; a practical manual for workers in pathological histology and bacteriology. tion of a second sterileblood-serum tube, next touched to the infected surface of the FIG. 19—Method of holding tubes dur-ing inoculation. 218 PATHOLOGICAL TECHNIQUE. first tube, and the wire thus infected gently and thoroughlyrubbed over the surface of the second. In a similar mannera third tube is then infected from the second, and then all thetubes placed in the incubator for eighteen to twenty-four is evident that comparatively few bacteria will be sown onthe medium of the second tube, and still fewer on that of thethird, so that the number of colonies which develop in thesecond tube will be less numerous than in the first tube,and those in the third tube still smaller in number. There-fore, in either the second or the third tube, or in both, thebacteria sown may be sufficiently few for discrete colonies todevelop from them, and among these there may be somecomposed of the bacterium which it is desired to one of such discrete colonies pure cultures may then. Fig. 20—Diluting cultures. be prepared as described above. The second and thirdtubes used in this method are called dilutions. Thedetails of the manner of manipulating the tubes, etc. in thismethod may be understood from the description given onpage 216 and from Fig. 20. The Plate Method of Petri.—Another method for obtainingdiscrete colonies of an organism from a mixed growth of sev-eral species is that known as the plate method of Petri. This isa modification of the original complicated method of Koch. The method consists in making dilutions in meltedagar-agar or gelatin tubes, and then pouring the infectedmedium into shallow glass dishes (Fig. 21) previously steril-ized, in which it is allowed to solidify. A few bacteria arethus distributed throughout a thin layer of culture-medium CULTURE METHODS. 219 in the dilutions, and the colonies which develop from themare then more or le
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