100 Proceedings of Royal Society of Edinburgh. [jan. 31, 
damaged ginger beer which was quite thick and jelly-like This 
injury was caused “ by a minute ferment which can easily be de- 
stroyed by salicylic acid ” (Gadd). 
1. Micrococcus prodigiosus. 
The spherical micro-organism ( Micrococcus prodigiosus) which 
has been found upon cooked and raw meat kept in the dark, was 
found on transplanting into 1000 c.c. of sterilised beef-broth 
(neutral) to grow well in the dark, and formed a thick pellicle on 
the surface of the liquid. On the addition of 0*2 grm. of salicylic 
acid to the broth, the growth ceased; and on transferring a portion 
of this broth into another flask containing sterilised broth, no 
Protoplasmic 
mass. 
M. prodigiosus. 
Ked oil globules 
in interstitial 
substances 
Fig. 2. — M. prodigiosus (zoogloea state) (much enlarged). 
development took place, not after remaining in this fluid at a 
temperature of about 34 C. for two weeks. I may say in passing 
that I have found that the red pigment produced by this “ chromo- 
genic micrococcus ” contains some compound of iron. On treating 
these organisms upon a slide under the microscope, with a weak 
solution of potassium sulphocyanate, a deeper red colour was pro- 
duced, no doubt due to the formation of ferric sulphocyanate. 
Again, when a solution of potassium ferrocyanide was run between 
the slide and cover-slip containing Micrococcus prodigiosus , a blue 
coloration was obtained of “ Prussian blue.” It appears from the 
above that the colour produced by this micro-organism is some 
iron compound. 
2. Micrococcus aurantiacus and Bacterium aeruginosum. 
I have also found that the salicylic acid solution proved fatal to 
Micrococcus aurantiacus and Bacterium aeruginosum , the micro- 
organisms found upon badly -made bread, that has been kept in a 
