150 THE HOUSE FLY—DISEASE CARRIER 
Ainsworth concludes, “It seems to me that enteric pre¬ 
vention naturally groups itself under five headings, 
namely, (i) Isolation of the human carrier, failing 
(2) elimination of the bacillus by means of some drug 
as yet undiscovered; (3) rendering excreta innoxious 
by disinfection, water carriage, and similar sanitary 
measures; (4) the establishment of immunity; and (5) 
the destruction of the go-between, to wit, the fly.” 
Cholera 
One of the earliest accurate scientific studies of the 
agency of insects in the transfer of human diseases was 
with regard to flies as spreaders of cholera. The be¬ 
lief in this agency long preceded its actual proof. Dr. 
George E. Nicholas (1873) is quoted by Nuttall as 
writing as follows regarding the cholera prevailing at 
Malta in 1849: 
“My first impression of the possibility of the trans¬ 
fer of the disease by flies was derived from the observa¬ 
tion of the manner in which these voracious creatures, 
present in great numbers, and having equal access to 
the dejections and food of the patients, gorged them¬ 
selves indiscriminately and then disgorged themselves 
on the food and drinking utensils. In 1850 the ‘Superb,’ 
in common with the rest of the Mediterranean squad¬ 
ron, was at sea for nearly six months; during the 
greater part of the time she had cholera on board. On 
putting to sea the flies were in great force; but after 
a time the flies gradually disappeared, and the epidemic 
slowly subsided. On going into Malta harbor, but 
