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 poad. 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 



