NOTES ON MICRO-ORGANISMS. 23 
boiled vegetables, and of some fruits such as melon, when left 
under bell-jars, standing in a plate of water. In this way I have 
obtained micrococcus forms giving red, yellow, and blue pigments. 
The best nourishing material is undoubtedly boiled white of egg, 
and this will yield them almost to a certainty. The spots of 
colour Bacteria can be picked off and resown. Lately I obtained 
a beautiful growth of Micrococcus violaceus in this way, covering 
quite half a square inch of surface. The colouring matter is 
external to the organism. 
Production of colouring matter is not confined to Bacteria, but 
is not unfrequently exhibited in mould growths, as, for example, 
in Penicillium, Aspergillus glaucus and niger, and some moulds 
that develop spindle-shaped compound spores. Neither in the 
case of colour Bacteria, nor with the colour-producing moulds, 
have the colouring matters been satisfactorily identified. They 
are said to show some relation to the Aniline dyes. At present 
they only help to identify a particular mould or Bacterium. 
Another interesting phenomenon, associated with the growth of 
some putrefactive organisms, is a phosphorescent or luminous 
appearance exhibited in the dark by meat and fish in a state of 
decomposition. Shell-fish show it very frequently. The organisms 
causing the appearance can be resown on animal substances, and 
again give rise to the characteristic appearance. It will be re- 
membered that some of the microscopic fungi have the same 
property, rotten wood occasionally showing it. Phosphorescence, 
whether in the animal or vegetable kingdom, is a very remarkable 
occurrence, and would afford an interesting field for study, for as 
yet very little light has been thrown on the matter. 
A great variety of products are obtained from Bacterial decom- 
position. Amongst the commonest are free acids, such as lactic, 
acetic, and butyric, formed from such substances as glycerine 
vegetable gums, starchy bodies, and the carbohydrates generally ; 
or we have a production of ammonia from certain nitrogenous 
bodies, or an oxydation of these last to nitric acid and nitrates, -a 
highly important action that is always going on in porous soils 
charged with sewage and decomposing animal and vegetable 
