ODORS AND LIFE. 189 
ted that these animals have a very highly-developed sense 
of smell. Scarpa, who has made admirable researches on 
this subject, found that they refuse food which is saturated 
with odorous substances, and, as an odd instance, that a 
duck would not swallow perfumed bread till after it had 
washed it in a pond. The waders, which have the largest 
olfactory nerves, are also those birds that display the great- 
est keenness of scent. Reptiles have very large olfactory 
lobes, leading us to believe that they discern odors readily, 
but at present we know little of the impressions they are 
sensitive to in this respect. Fish also have an olfactory 
membrane. Fishermen have always remarked that they 
may be attracted or driven off by throwing certain odorous 
substances into the water. Sharks, and other voracious fish, 
collect in crowds and follow from very far about a body 
thrown into the sea. It is even said that, when blacks and 
whites are bathing together in latitudes where these fish 
abound, they particularly single out and pursue the more 
strongly odorous blacks. Nor are the crustacea indifferent 
to emanations which act on the olfactory nerve. The 
method used for attracting and taking crabs is familiar. 
Regarding the lower animals, we have only still more 
uncertain information, except as to insects. Entomologists 
maintain that scent is very delicate in most insects, and rely 
on plausible conjectures on this subject, but they do not as 
yet know what the seat of the sense of smell in insects is. 
When meat is exposed to the air, in a few moments flies 
make their appearance in a place where none had before 
been seen. If refuse matter or bodies of animals are left 
on the ground, insects flock to them at once, feeding on 
such substances, and depositing their eggs in them. Scent 
alone seems to guide them, exclusively of sight even, for, 
if the object of their desire is hidden, they easily manage 
to find it. A curious fact as to the scent of insects is fur- 
nished by those kinds that prefer decaying substances. A 
