114 INSECTS AND DISEASE 
that I have described. But it may be communicated 
artificially by the direct inoculation of the blood of a patient 
suffering from the disease. Nevertheless, the most refined 
microscopical and cultural methods have not been successful 
in revealing in this blood the living organism that causes 
the fever. The germ of yellow fever still rema'ns undis- 
covered. There is indeed good evidence that it is ultra- 
microscopic, for, unlike the smallest living organisms 
discovered by the microscope, it passes through the pores 
of a Berkefeld filter. The discovery of its method of pro- 
pagation depends entirely on experiment, and is indeed 
one of the best instances of the application of the experi- 
mental method in medicine. As such, it is one of the 
greatest triumphs achieved in modern times in the prevention. 
of one of the most deadly epidemics known to afflict 
mankind. 
RATS, FLEAS, AND PLAGUE. 
‘Early in 1900, Australia was invaded by the plague. 
Human nature is so constituted as to tolerate with 
indifference and apathy those epidemic diseases which are 
familiar, but to fly into a panic at the mere report of those 
which are novel. In the present instance, panic was doubly 
inevitable, for the plague had been practically unknown 
for centuries among European peoples, and the very name 
was charged with the vague terrors of old epidemics ; and 
particularly with recollections of the great plague of London 
in the seventeenth century, described by De Foe, an author 
distinguished for his talent in writing fiction so realistic 
in style, as to be indistinguishable from the facts, which 
are no doubt imbedded in his narrative. 
At this juncture, I was appointed a special medical 
officer by the Government to advise and report regarding 
the epidemic in Northern and Central Queensland, some 
cases of plague having been reported in Rockhampton 
and Townsville. My first duty was to visit Sydney, where 
plague had been rife for several months, to acquire informa- 
tion. The situation, as 1 found it in that city, was certainly 
remarkable. On the one hand were a populace and a 
Government treating plague as a virulently infectious 
disease to be stamped out at any cost, regardless of expense, 
