YELLOW FEVER EXPEDITION 
557 
These sites, with possibly the main sewers which are constantly fed from gutters, 
etc., filled with larvae, seem to be the chief breeding-places about the paved part of the 
town ; the gardens, often with fountains and circular water troughs round the plants 
for keeping off the destructive Sauba ant, also require attention for they form a fertile 
source of S. fasciata. In the unpaved parts, naturally, there are many odd pools 
from time to time, those of natural origin from the configuration of the ground, and 
those due to obstructions in the roadside channels, especially the unconcreted ones. 
The pools in which Anopheles larvae were found, as mentioned elsewhere, are 
eminently adapted for treatment by filling up on account of their small and shallow 
nature ; a complete survey of these is required. Living specimens of the larvae 
and adults of the Anopheles were shewn to many of the local medical men and 
others. 
Experiments were intended, but never carried out owing to stress of other things, 
to try the culicicidal effect of poisonous plants in the local flora. About Para are 
numerous examples of the Solanaceae (for instance, the 'jurubeba ' Solatium grandi- 
florum), and if means like the leaves or other parts of common local plants will act, 
when placed in casual waters from which drinking supplies are not obtained, by killing- 
contained mosquito larvae, a simple and economical warfare can be waged on the 
insects without much exertion. 
A few words may be said about mosquitoes on the ships about Para. It is said 
by captains that mosquitoes only commence to come on board when the lighters 
which are used for the discharge of the cargo are brought alongside. Seeing that the 
anchorage for the large ships is some two miles below the city, and the lighters lying 
about the neighbourhood of the city are brought to wharfsides for discharge, they 
are a means of bringing city mosquitoes to the ships. On examination, several ot 
the large barges (which are covered with a rainproof metal cover) were found to 
harbour a certain number of the insects, both S.faciata and C. fatigans were found 
in the adult condition and a few larvae of the former in the bilge water ; but these 
lighters had recently been cleaned up and painted ; open lighters are also used, these 
were seen to contain abundant rain water and tar and oily material from the coal for 
which they are used ; no larvae were found in them. 
During my trip up to Manaos, indiscriminate collection of all and any mosquitoes 
that could be found on board was made. Although a number were collected it was 
not until after anchoring at Manaos and the lighters came alongside that the species 
S. fasciata was taken. It appears that the method of discharge by means of lighters 
may be almost as risky for the importation of mosquitoes infected in the city, as if the 
vessel was actually brought to the wharfside. The only recommendation that seems 
likely to be effectual would be to fumigate the lighters some time before they were 
brought alongside by burning sulphur within them. 
T I 
