igo SMELLS AND PERFUMES 



remaining in the mouth. The volatile odoriferous matter 

 of the onion is absorbed into the blood. It passes out first 

 through the lungs and later through the small fat-forming 

 glands in the skin. It is difficult to ascertain how far 

 animals derive their odours in this way in a complete state 

 from their food, and how far they chemically construct 

 them afresh by their own activity. No doubt both 

 processes occur ; but in plants the odorous bodies are built 

 up entirely by the chemical action of the plant itself upon 

 simple salts of carbonic acid, ammonia and nitrates. 

 Animals can certainly take highly elaborated chemical 

 bodies into their digestive organs without destroying them 

 and absorb them unchanged into the blood and deposit 

 them in the tissues. Thus the canary is made to take up 

 the red colour of cayenne pepper and deposit it in the 

 feathers. Thus the green oysters of Marennes acquire 

 their colour from minute blue plants (diatoms) on which 

 they feed. And thus, too, the canvas-backed ducks of the 

 United States take into their tissues the odorous matter 

 of celery, and our own grouse the flavour of heather, whilst 

 fish-eating birds and whales in this way acquire a fishy 

 taste. So, too, the flounders and the eels of the Thames, 

 and even salmon in muddy rivers, acquire a taste like the 

 smell of river mud. It is probable that many of the odours 

 of animals (but by no means all) are thus derived directly 

 from their food, or are produced by very slight changes of 

 the odorous bodies absorbed in food. Mutton and beef 

 owe their savour in some degree to the scents of the 

 grasses on which sheep and oxen feed. And it is not im- 

 probable that the sheep-like smell which the Chinese detect 

 in the European, comes to the latter direct from his 

 general use of the sheep as food. 



Plants are the great chemical manufacturers in the world 

 of life, and second to them come our human industrial and 

 scientific chemists. And though we must claim for animals 



