More Science From an Easy Chair

flavours) are not matters of general agreement. Thus the smells of garlic and of onions, and even of assaf?tida, are to many men among the most attractive and appetising in existence-to ve

d, but by a smell like that of putrid meat, which so far misleads blue-bottle flies as to cause them to lay their eggs on the reeking blossom. So diverse are the tastes of men and animals in these matters that it is remarkable

e mathematical laws as to harmony and melody in sound and colour which affect animals and ourselves to a large extent similarly. Sweets are agreeable and bitters are disagreeable, though it is the fact that the snail, which loves sugar, recoils from saccharine, and there are "mites" (Acari) which feed with avidity on bitter strychnine! Excess of heat and of cold is disliked by animals and all men, whilst the sense of touch is pleasurably or painfully affected in much the same way in most men and animals, more than is the case with regard to any other of the senses. The sense of smell depends up

strange surroundings, solitude). Hence it is intelligible that the man accustomed to garlic or onions in his food is strongly attracted by their smell. So too the man whose tribe or companions have learnt by necessity to eat slightly putrid meat, fish, and cheese is attracted by their odour, though for others these odours are associated rather with what is poisonous and injurious. The dislike of the smell of sewer-gas and foul accumulations of refuse was not known to former generations of men (even in European cities a couple of hundred years ago) any more than it is to-day to the more unfortunate poorer classes, to many modern savages, to hyenas, and several other animals and b

produce phosphorescent light in special organs so as to attract the opposite sex. Again, we find that the red-coloured oxygen-seizing crystalline substance h?moglobin exists in the blood of a vast number of animals, and might as well be green or colourless for all the good its colour does them. Yet here and there the splendid red colour which this chemical gives to the blood becomes of great importance as a "decoration," or "sex-ornament." The comb of the domestic fowl, the watt

cumbers: the green-bone fish and the mackerel smell alike. One of the common earth-worms has a strong aromatic smell, and the common snail, as well as the sea-hare and one of the cuttle-fishes (Eledone), smells like musk. Musk itself is produced, as a scent attracting the opposite sex, by several animals-musk-deer, musk-sheep, musk-rats. I am not now attempting to enumerate the well-recognised odours of animals such as are extracted from them by man in order to "opsonize" himself, but am pointing to the more obscure cases. There is not a very great or marked variety in the odours of fishes; but reptiles with their dry, oily skins give off various aromatic smells, none of which are valued by man. Toads have distinct odours, and one kind (Pelobates fuscus, or the heel-clawed toad), common in Europe, but not British, is known locally as the garlic toad on account

l changes set up in secretions of the body-surface by bacteria. Several distinct repulsive smells liable to occur on the human body are due to want of cleanliness in destroying bacteria by proper antiseptics. The fatty and waxy secretions of the skin are often decomposed by bacteria, even before complete extrusion from the glands in which they are formed, whilst the decomposition of food in the mouth and intestines by bacteria alters materially both the natural

his 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

must claim for animals some power of manufacturing distinct odorous bodies from inodorous nutritive matter assimilated by them, it is probable that in

ttle-fishes (the Eledone moschata) has a strong odour of musk, and it is possible that ambergris owes its perfume to the musk-like scent of the cuttle-fish eaten by the whale in whose intestine it is formed. Another "smell" which is extremely mysterious is that produced by two quartz-pebbles, or even two rock-crystals, or two pebbles of flint or of corundum, when rubbed one against the other. A flash of light is seen, and this is accompanied by a very distinct smell, like that given out by burning cotton-wool. It is demonstrated-by careful chemical cleaning before the experiment-that this is not due to the presence of any organic matter on or in the stones or crystals used. It seems to be an exception to the rule that "odo