BY n. GREICi-^^MITiI. 



53 



It was noted, but this may be of no importance, that the ropy infusions were 

 slow to show gi-owths of moukls on the surface of the fluids, while all the non- 

 ropy tests soon became covered with mould. Possibly the ropy bacterium 

 utilised all the available carbohydrate. 



The ropy fluids in both of the positive tests contained many bacteria capable 

 of forming slime on dextrose media, but only one of the numerous forms pro- 

 duced ropy colonies and the same organism was found in both positive tests. It 

 gave a canary-coloured, loose, slightly raised growth on nutrient agar, and under 

 the microscope appeared as a round yellow colony with central granules and 

 homogeneous periphery. The bacterium was gi-own in bouillon and after some 

 time another bacterium of identical form but with different cultural characters 

 appeared. This was at first supposed to be an impurity in the original colony 

 but the same supposed impurity appeared in both races and in others obtained 

 at a later date from bark. The supposed impurity was subsequently recognised 

 as a phase of the original organism. Al . 



The ropy organism first isolated and set aside for future examination will be 

 referred to as B., the most active phase of which is P>2. The organism isolated 

 later and obtained several times from wattle-bark will be called A. Both bacteria 

 exist in phases best recognised by the appearance of the colonies growing on the 

 surface of nutrient agar. There is the primary phase, such as Al, a weak rope- 

 produeer, which can be altered into the strong rope-producer, A2 . The change of 

 phase is not abrupt and transition phases are met with. Some of these, generally 

 yellow in colour by transmitted light, are closer related to Al, others, grey or 

 smoky, are nearer akin to A2. The phase Bl was occasionally noted but, as com- 

 pared with A2. B2 is remarkably stable. 



The ropy bacterium, mixed i)ossibly with the altered phase, readily developed 

 ropiness in nutritive solutions containing dextrose, but did not have any apparent 

 acti(m upon a sterilised infusion of wattle bark. In case the infusion had been 

 altered by the sterilisation and become unsuitable tor tlie development of the ropy 

 substance, the bacteria were grown in pasteurised infusion, then in infusion 

 stei-ilised by filtration through porcelain and finally in raw infusion, but in none 

 of these was there any trace of ropiness. This was rather aggTavating but cjuite 

 in keeping with certain earlier attempts to transfer the ropiness of the original 

 infusion to bottles containing healthy infusions. Unless a mass infection were 

 made, the ropine-ss could not be transferred, and one had the suspicion that the 

 ropy substance had not increased, but had simply become more diffuse. 



The explanation of the apparent anomaly was found after it had been shown 

 that the slime or ropy material was coagulated by tannic acid. It follows from 

 this observation that in the original case the ropiness had developed liefore much 

 tannin had passed into the water, otlierwise the slime ])roduced by the bacteria 

 would have been coagiilated upon the bodies of the bacteria, and would have pie- 

 vented them becoming distributed in the bulk of the liquid. To prove the rea- 

 soning, wattle bark, sterilised at 130°. was covered with water, seeded with the 

 bacterium, B2, and incubated at 28°. In sixteen hours a ropy infusion was ob- 

 tained. A repetition gave the same result. 



So far we have arrived at the stage that ropiness is developed in weak in- 

 fusions of bark substance and not in strong, and it remained to determine the 

 amount of tannin wliich would permit or prohibit the production of slime. 



On account of the inability to obtain a pure tannin, tannic acid was employed 

 in the experimental wdik with s^Tithetic media. TVattle bark infusion contains 



