[81] Dr. A. C. Houston has been kind enough to make an examination of B. erodiens, and to ascertain its action on various sugars. It produces fluorescence in neutral-red broth cultures, acid and gas in lactose cultures, indol, and acid, and clot in milk cultures. It ferments dulcite with production of acid, but _not_ cane sugar, adonite, inulin, inosite, salicin, or raffinose.
B. erodiens does not secrete any tryptic enzymes, hence its action on the skin is to be attributed either to an intracellular enzyme, or to its chemical products, which, being secreted _in situ_, have a more favourable and powerful action than if merely added to the bating liquid. It was for this reason that I proposed to use a mixed culture of bacteria, especially bacteria from the sweating process (see p. 105), which secrete a mild form of proteolytic ferment, capable of dissolving the more easily soluble portion of the skin fibres (or certain constituents), but not capable of attacking the hyaline layer.
--------+-------+-------------+--------+---------------------------+------------ No. of | | Shape | | | Growth the Bac-| Where | and |Motility| Growth on Gelatin | on terium | Found | Arrangement | | | Agar-agar --------+-------+-------------+--------+-----------------------------------+---- 1 |Dog |Small rods |Lively |In the gelatin stab-culture|A white |dung |of the size | |the bacteria show a good |surface | |of the _Bac. | |growth in the depth. At the|layer is | |prodigiosus_.| |surface it forms a small |formed on | | | |white button. The gelatin |inclined | | | |is not liquefied. The col- |stiffened | | | |onies which have reached |agar-agar. | | | |the surface of the gelatin-| | | | |plate spread in the shape | | | | |of a leaf, with a mother- | | | | |of-pearl-like gloss. | | | | | | 2 | Do. |Small rods of| Do. |Stab-culture: The germs |A yellowish- | |the size of | |develop along the entire |white layer | |the hay | |track. Small arms extend |is formed | |bacillus. | |sideways into the gelatin. |along the | | | |A white layer is formed on |inoculating | | | |the surface. The gelatin is|stab. | | | |slowly liquefied. | | | | | | | | | |Gelatin-plate: When they | | | | |reach the surface, the col-| | | | |onies spread out in the | | | | |shape of a leaf and then | | | | |are slightly fluorescent. | | | | | | 3 | Do. |Very small | Do. |Stab-culture: Very good |A white | |rods rounded | |growth in depth. Very many |deposit is | |at the | |arms extend laterally from |formed on | |ends. | |the track of the stab into |inclined | | | |the gelatin. Small knots |agar-agar. | | | |are formed at the ends of | | | | |the arms. A thin white | | | | |coating is formed on the | | | | |surface. Gelatin is not | | | | |liquefied. | | | | | | | | | |Gelatin-plates: The colon- | | | | |ies located deeper down | | | | |appear as pale-yellow small| | | | |round disks, which gradual-| | | | |ly work up toward the sur- | | | | |face and there form circu- | | | | |lar disks which show larger| | | | |dots in the middle. | | | | | | 4 | Do. |Small rods as|Slow |The gelatin stab-culture |Heavy white | |large as hay |movement|resembles that of the hay |deposit on | |bacilli. | |bacillus, while the growth |the entire | | | |in the gelatin-plate more |surface. | | | |resembles that of the an- | | | | |thrax bacillus. Threads ex-| | | | |tend from the liquid colon-| | | | |ies which have been let in,| | | | |which threads are at first | | | | |braided and twisted, and | | | | |later on extend straight | | | | |into the gelatin. | | | | | | 7 | Do. |Small rods |Lazy |Stab-culture: Strongly li- |White | |similar to | |quefying. A white skin |unevenly | |the hay | |forms on the surface. Along|thin layers | |bacillus. | |the liquefied prick are ra-||withspurs. | | | |diations into the solid | | | | |gelatin. | | | | | | | | | |Gelatin-plate: Quickly li- | | | | |quefying colonies which | | | | |form a white skin at the | | | | |top. | | | | | | 11 | Do. |Medium-sized |Motile |Stab-culture: A white coat-|A white | |small rods. | |ing is formed on the sur- |deposit | | | |face. The gelatin is not |along the | | | |liquefied. The bacteria |puncture. | | | |grow well in the depth. | | | | | | | | | |The colonies which come to | | | | |the surface spread out | | | | |leaf-like with a mother-of-| | | | |pearl-like gloss. | | | | | | 12 |Dog |Medium-sized |Lively |Stab-culture: Grows evenly |Heavy white |dung |small rods. | |along along the track. Ge- |deposit; | | | |latin is not liquefied. A |glossy. | | | |thin glossy deposit on the | | | | |surface. | | | | | | | | | |Gelatin-plates: The lower- | | | | |lying colonies appear as | | | | |pale-yellow circular small | | | | |disks.