ODORS AND THE SENSE OF SMELL. 689 



ground of a few square millimetres is enough to enable the dog 

 to follow the scent. In birds, the sense of smell appears to be 

 little developed ; in mollusks and insects the smelling apparatus 

 has been located in the antenna?. Below the group of worms, no 

 olfactory reactions have been, so far as I know, definitely estab- 

 lished. 



The mechanism of the olfactory apparatus is, as a whole, 

 simpler than that of sight and hearing ; but the sensation is sub- 

 ordinated to many individual anatomical peculiarities. As much 

 can be said of touch and taste, which require contact of the 

 excitant, while sight and hearing merely register the vibrations 

 transmitted by a medium. It is easy to conceive how the con- 

 dition of the membranes, the form of the nasal passages, etc., 

 may affect the sensation. 



A distinction is made in medicine between respiratory anos- 

 mias which depend on the formation of the organs and the 

 condition of the connective tissues, and essential anosmias which 

 result from atrophy of the nerves. Anosmias are frequent ; some 

 are congenital, many are senile and temporary, and connected 

 with traumatisms, hemianesthesia, aphasia, and hemiplegia. We 

 can not expect to find as concordant reactions for the smell as for 

 the sense of color or the sense of form. It is nevertheless a matter 

 of interest to investigate, on as good subjects as we can get, the 

 influence of different odors on sensibility ; or, in other words, to 

 determine the weight of odorous vapor which it is necessary to 

 breathe and accumulate in the nasal f ossse to make a perfume per- 

 ceptible. That is the purpose of olfactometers. The olfactometer 

 gives, besides this, the intensity of a perfume. The larger the 

 perceptible minimum of a perfume, the less intense the perfume 

 is, and it is this intensity which determines the price of a per- 

 fume, the delicacy of its odor being the same. 



The olfactory sense is followed by effects of different kinds 

 of intensity from those of sight and hearing, and may be accom- 

 panied by a kind of poisoning. The old medical books are full of 

 stories of it. There are those of a girl killed by the exhalations 

 of violets; of a woman seized with a violent headache from 

 sleeping on a bed of roses ; and of a girl who lost her voice by 

 smelling of a bouquet. Ancient medicine attributed curative 

 properties to perfumes, particularly to those of the rose, musk, 

 and benzoin. The intensity of the effects of perfumes makes a 

 rapid succession of sensations almost impossible ; for consecutive 

 odors cause a rapid anesthesia of the sense ; on the other hand, 

 if the times separating two successive sensations are too long, it 

 becomes impossible to combine them, and the anticipated effect 

 is disturbed by strange feelings. In short, smell is rather the 

 complement of other excitations than an artistic excitation like 



VOL. XLI. 50 



