164 J. B. CLELAND. 
The success of the fence traps is so great in comparison that 
the question of favus can be dismissed. 
Though, towards the end of the visitation, mice were said 
‘to be dying from disease, there is no clear evidence that 
such was the case, or, if it was so, as to the nature of the 
disease. The subcutaneous abscesses, though doubtless 
crippling, and perhaps finally killing, the affected mice, 
did not seem capable of reaching epizootic proportions. 
The various rat-viruses, members of the food-poisoning 
eroup of the great coliform family of bacilli, have been 
suggested from time to time for the purpose of destroying 
rats and mice. My experience of a number of strains of 
these is highly disappointing. Though with: gross feeding 
we have been able at times to kill rats or mice under labora- 
tory conditions, at other times we have signally failed. We 
have not been able to produce an epizootic in caged animals. 
If such a fatal epizootic as plague makes but a slight dimi- — 
nution in rats, and certainly does not exterminate them, 
can we expect material help from a less virulent organism 
such as one of this group? Still every little might help, 
and it was decided to test the matter as regards the pest 
mice under field conditions in this State. Four different 
strains, one recently obtained, were tried by us in a country 
centre in July, 1917. In spite of liberal. baitings with the 
organisms, which baits the mice were seen eating, no notice- 
able decrease in their numbers could be recognised. They 
were, of course, confined within a limited space. I am in- 
clined to think that the good effects reported of these vi- 
ruses, under collateral but not identical conditions, were 
coincidences, and not consequences. 
The natural enemies of mice in Australia, such as snakes, 
monitor lizards, cats, dogs, and certain birds, probably play 
some part in keeping the numbers down under ordinary 
conditions. These can play little part when abundance of 
