KB, 5 Roberg: Bacterial Infections 327 
present, in order to isolate them on Dieudonné’s medium. When 
four or five flies were employed, it was necessary to enrich the 
vibrios present in only one or two changes of Dunham’s peptone 
solution. 
OUTLINE OF EXPERIMENTS 
SERIES I. BIOLOGICAL FEATURES 
On the evening of March 29 four traps were set to catch flies, 
with the object of securing Apiochxta ferruginea and to breed 
them after their eggs had been deposited upon the substances 
contained in the traps. 
Three of these traps consisted of wide-necked 8-ounce bottles, 
containing a perforated stopper in which was placed the stem of 
a glass funnel. Over the orifice of the funnel was stretched a 
single layer of cloth gauze, having 20 squares to the linear inch. 
The fourth trap consisted of a 6-inch beaker, over which was 
stretched a layer of the same gauze. . 
Into each of the three bottles were placed, respectively, the 
following food substances for breeding the flies: agar-agar, a 
mixture of human feces and melted agar, and a dead snail. In 
the beaker was placed a mixture of human feces and melted 
agar. 
On the following morning (March 30) these traps were set 
at 5-foot intervals in a room, carefully screened with wire netting 
(having 16 squares to the linear inch), which prevented larger 
flies from entering the room. 
In the vicinity of the beaker, which smelt strongly of feces, 
there began soon to appear a few small flies which could scarcely 
be seen at a distance of 3.5 meters. During the course of the 
day great numbers of these hovered about the beaker; some were 
seen to alight upon the surface of the gauze, readily pass through 
into the beaker, and settle upon the feeces-agar mixture, which 
they greedily devoured. 
The bottle trap which, also, contained a feces-agar mixture, 
smelt less strongly, and fewer flies were seen hovering about it. 
Some of them passed through the gauze and into the bottle. 
The bottle containing the dead snail smelt of putrefaction, but 
fewer flies were seen there than in the two previous traps. 
The bottle containing plain agar attracted no flies. 
On the morning of March 31 a considerable number of flies 
were still in the bottle and beaker which contained the feces- 
agar mixture. These were covered to prevent further ingress 
or egress of flies and kept for observation. 
The bottle containing the dead snail contained only a few 
flies. This was covered. 
