ODOURS. 165 



membrane of the tongue. It was conceived that the shape of the mole- 

 cules of a pungent odour is pointed, that of an agreeable one, round. 

 Others, again, were of opinion, that olfaction is owing to some chemi- 

 cal union between the odorous molecule and the nervous fluid, or be- 

 tween it and the nasal mucus. None, however, have attempted to 

 specify the precise chemical composition that renders a body odorous. 

 The sensations do not present the most favourable occasions for exhi- 

 biting chemical agency ; and, in this particular sense, it is probably no 

 farther concerned than in the sense of touch; and not so much as in 

 that of taste. It is sufficient for the odorous particle animal, vege- 

 table, or mineral to come in contact with the olfactory nerves, in 

 order that the odour shall be appreciated ; and we may, in vain, look 

 for chemical action in many of those animal and vegetable perfumes, 

 as musk, amber, camphor, vanilla, &c. which astonish us by their 

 intensity and diffusibility. 



The same remarks, that were made on the classification of savours, 

 are applicable to that of odours. They are not less numerous and 

 varied ; and each substance, as a general rule, has its own, by which 

 it is distinguished. Numerous attempts have been made to group them; 

 but all have been unsatisfactory. The classification proposed by Lin- 

 nseus, 1 was into Odores aromatici, those of the flowers of the pink, 

 bay leaves, &c. ; 0. fragrantes, those of the lily, jessamine, &c. ; 0. 

 ambrosiaci, those of amber, musk, &c.; 0. alliacei, those of garlic, 

 assafoetida, &c. ; 0. hircini, (like that of the goat,) those of the Orchis 

 hircina, Chenopodium vulvaria, &c. ; 0. tetri, repulsive or virous, 

 those of the greater part of the family solanese; and lastly, 0. nau- 

 seosi, those of the flowers of the veratrum, &c. A simple glance at 

 this division will exhibit its glaring imperfections. No two persons 

 could agree to which of any two of the cognate classes a particular 

 odour should be referred. None of the other classifications, that have 

 been proposed, are more satisfactory. M. Fourcroy divided them into 

 extractive or mucous, fugaceous oily, volatile oily, aromatic and acid, 

 and hydro sulphureous ; and Lorry into camphorated, narcotic, ethe- 

 real, volatile acid, and alkaline. The distinction into animal, vegetable, 

 and mineral, is not more commendable. Musk is the product of an 

 animal of the ruminant family ; but the odour is not confined to that 

 animal. It is contained in the civet; in the flesh of the crocodile; and 

 in the musk-rat. Haller asserts, that his own perspiration smelt of it. 

 It is met with, likewise, in the vegetable kingdom; in Erodium mos- 

 chatum, in the seeds of Abelmoschus, the flowers of Rosa moschata, 

 and Adoxa moschatellina, and in some of the varieties of the melon 

 and pear; and, what is perhaps more surprising, in mineral sub- 

 stances; as in certain preparations of gold; and in some earths of 

 which tea-pots are made in China and Japan. The odour of garlic, 

 again, is found not only in that vegetable, but in assafoetida, in 

 arsenic, when thrown upon hot coals ; and in Bufo pluvialis, a species 

 of toad. 



In by far the majority of cases, we can only designate an odour by 



1 Arncenitat. Academic. Erlang, 1787, 1790. 



