748 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XLIII. — On the Development of Mixed Cultures of Bacteria and 
Lower Fungi in Liquid and Solid Media. By Emil Wester- 
gaard, Lecturer on Technical Mycology, Heriot - Watt College, 
Edinburgh. 
[. Preliminary Notice.] 
An investigation was undertaken in order to ascertain to what extent and 
in what manner the individual species and varieties of lower fungi and 
bacteria present in liquid and solid media affect the simultaneous develop- 
ment of other similar organisms. The preliminary experiments were carried 
out with a culture of streptococcus lactis acidi, which was added in varying 
proportions to cow’s milk immediately after milking, and gelatine plates 
were made at once, partly from the milk to which the cultures had been 
added and partly from the natural milk. The gelatine employed contained 
either glucose and peptone (Witte), or in addition an excess of calcium 
carbonate. The proportion in which the culture was added to the milk 
varied from 1 c.c. in 500 c.cs. of milk to one drop of the culture in half a gallon 
of milk. The results were in all cases practically the same, namely, that 
the plates infected with the normal milk gave an abundant development of 
bacteria and were in all cases rapidly liquefied, whereas the plates made 
from the infected milk showed a far less varied bacterial contents and a 
total suppression of the liquefying species. 
The results obtained with the plates containing an excess of calcium 
carbonate were the same as those obtained with the plates which did not 
contain this, showing that the observed results are not due to any formation 
of free lactic acid. The most probable explanation of the facts just 
mentioned seems to be the production of anti-enzymes which, by binding 
the proteoclastic enzymes of the liquefying species, prevent the development 
of the latter. This view seems to find some support in the fact that 
spontaneously soured milk as a rule ultimately undergoes proteoclastic 
decomposition (i.e. after the lactic acid bacteria have been paralysed by the 
free acid). 
The experiments are now being continued with a number of pure 
cultures of well-known bacteria and lower fungi, and an endeavour is being 
made to demonstrate the presence of the anti-enzymes referred to. 
( Issued separately December 2 , 1909 .) 
