934 
diffuses through the agar, evidently without spontaneously oxidising 
at the air. 
From the foregoing it is clear that Actenomyces, as well as the 
bacterium, can only be found in garden soil when germs of both 
species occur in each other’s immediate vicinity. To promote this 
occurrence I have tried first on fit agarplates to grow Actinomyces 
and later floated them with a tyrosin solution, in which the melanin 
bacterium was present in so great quantity, that it could develop 
anywhere on the plate, after the tyrosin had diffused. 
As the various species of Actinomyces are very vigorous, poly phagous 
microbes, which develop especially in dilute media at the side of 
the common bacteria, the most different food may be used for the 
first part of the experiment. 
So, an agarplate, only containing some potassiumfosfate and ammo- 
niumsulfate, was sprinkled with a little dry inulin mixed with garden 
soil. The soon developing flora was washed off under the tap by 
which the loosely adhering bacterial colonies together with the non- 
decomposed inulin, were removed. The agarplate was now clear 
again but in the surface were hundreds of Actinomyces colonies 
which had not been removed by the washing, as they had penetrated 
too deep into the agar. After treating with the tyrosin solution in 
which the melanin bacterium was suspended and a renewed culti- 
vation for some days at 30° C., black melanin spots appeared around 
some six colonies of Actinomyces; this species must thus be rather 
common in the soil. 
The tyrosin Actinomyces can also very easily be isolated from the 
roots of the elmtree (Ulmus campestris), in whose dead periderm 
cells an almost pure Actinomyces flora occurs, as | demonstrated 
before '). For the development of this flora some of the hairroots are 
carefully washed, to remove the adhering soil and are then ground 
in a mortar. The thus obtained brown paste is diluted with water, 
mixed with the tyrosin bacterium (which however is also rather com- 
mon on the elm roots themselves), then sown out on a tyrosinplate 
of the above composition. After a few days numerous colonies of Acti- 
nomyces develop at 30°C., among which some jet-black ones. 
Here it should be called to mind that the two organisms produce 
no pigment on peptone or broth-containing media, neither each for 
itself nor in combination. But herefrom cannot be concluded that 
at their cultivation from peptone no tyrosin originates. Nevertheless the 
conclusion must be drawn, that if at the splitting of the peptone 
1) Centralbl. f. Bakter. 2 Abt. Bd. 6, S. 2, 1900. Arch. Néerl. 1900, p. 327. 
