We are here in the presence, it may be insisted, not of a nervous influence only, but of a direct effect of odor on the vital processes.  The experiments of Tardif on the influence of perfumes on frogs and rabbits showed that a poisonous effect was exerted;[83] while Fere, by incubating fowls’ eggs in the presence of musk, found repeatedly that many abnormalities occurred, and that development was retarded even in the embryos that remained normal; while he obtained somewhat similar results by using essences of lavender, cloves, etc.[84] The influence of odors is thus deeper than is indicated by their nervous effects; they act directly on nutrition.  We are led, as Passy remarks, to regard odors as very intimately related to the physiological properties of organic substances, and the sense of smell as a detached fragment of generally sensibility, reacting to the same stimuli as general sensibility, but highly specialized in view of its protective function.

The reality and subtlety of the influence of odors is further shown, by the cases in which very intense effects are produced even by the temporary inhalation of flowers or perfumes or other odors.  Such cases of idiosyncrasy in which a person—­frequently of somewhat neurotic temperament—­becomes acutely sensitive to some odor or odors have been recorded in medical literature for many centuries.  In these cases the obnoxious odor produces congestion of the respiratory passages, sneezing, headache, fainting, etc., but occasionally, it has been recorded, even death. (Dr. J.N.  Mackenzie, in his interesting and learned paper on “The Production of the so-called ‘Rose Cold,’ etc.,” American Journal of Medical Sciences, January, 1886, quotes many cases, and gives a number of references to ancient medical authors; see also Layet, art.  “Odeur,” Dictionnaire Encyclopedique des Sciences Medicales.)

An interesting phenomenon of the group—­though it is almost too common to be described as an idiosyncrasy—­is the tendency of the odor of certain flowers to affect the voice and sometimes even to produce complete loss of voice.  The mechanism of the process is not fully understood, but it would appear that congestion and paresis of the larynx is produced and spasm of the bronchial tube.  Botallus in 1565 recorded cases in which the scent of flowers brought on difficulty of breathing, and the danger of flowers from this point of view is well recognized by professional singers.  Joal has studied this question in an elaborate paper (summarized in the British Medical Journal, March 3, 1895), and Dr. Cabanes has brought together (Figaro, January 20, 1894) the experiences of a number of well-known singers, teachers of singing, and laryngologists.  Thus, Madame Renee Richard, of the Paris Opera, has frequently found that when her pupils have arrived with a bunch of violets fastened to the bodice or even with a violet and iris sachet beneath the corset,