Fig. 127.—Novy jars.
It must be remembered that facultative anaërobes as well as anaërobes will grow under any of the above conditions, so that cultures of organisms so obtained must be further tested aërobically in order to determine to which group the organisms belong.
Reference has been made above to the “inoculation” of culture media, which means introducing into the medium used the desired material in the proper way. For small quantities this is most conveniently done with platinum “needles,” that is, pieces of platinum wire inserted into the ends of glass rods. The “straight” needle is a piece of heavy platinum wire of about 0.022 inch in diameter ([Fig. 128]). It is used most frequently to inoculate all forms of solid media. The platinum loop is of lighter wire, 0.018 inch. The loop in the end is conveniently made by twisting the wire around the lead of an ordinary lead-pencil. The “loop needle” ([Fig. 129]) is most used in transferring liquid media. On account of the high price of platinum, the author has substituted “nichrome” wire for student use. This is stiffer, not so easily made into loops and breaks out of the rods more easily. The latter defect is remedied to some extent, by imbedding the wire only slightly for about one-fourth of an inch on the side of the end portion of the rod. The low cost, less than one-twentieth of platinum
, justifies its use.
Fig. 128.—Straight needle.
Fig. 129.—Straight and loop needles.
Fig. 130.—Pasteur flask—“ballon pipette.”