190 NATURE AND LIFE. 



beautiful arum is found in our woods, the cuckoo-pintle, 

 whose white flower diffuses a disgusting odor. Now, the 

 inside of this flower is often filled with flies, snails, and 

 plant-lice, seeking the putrid source of this fetid smell. We 

 may see the little creatures, in quest of their food or of a fit 

 place to lay their eggs, move about in all directions, and quit 

 most unwillingly the flower whose scent has misled them. 



II. 



Having thus learned what physiologists think of the 

 sense of smell and the conditions of the perception of odors, 

 let us see what naturalists and chemists have ascertained 

 respecting the latter as viewed in themselves, what place 

 they give to odorous bodies, and what character they at- 

 tribute to them all. The three kingdoms possess odors. 

 Among mineral substances, few solids, but quite a number 

 of liquids and gases, are endowed with more or less power- 

 ful scents, in most cases not very pleasant ones, and usually 

 characteristic. Those odors belong to simple substances, 

 such as chlorine, bromine, and iodine ; to acids, as hydro- 

 chloric and hydrocyanic acid ; to carburets of hydrogen, as 

 those of petroleum ; to alkaline substances, ammonia, for 

 instance, etc. The odors observable among minerals may 

 almost all be referred either to hydrocarbonic or hydrosul- 

 phuric gases, or to various solid and liquid acids produced 

 by the decomposition of fats, or to peculiar principles se- 

 creted by glands, such as musk, ambergris, civet, and the 

 like. Vegetables present quite another variety of odors, 

 from the faintest to the rankest, from the most delicious to 

 the most disgusting. Absolutely scentless plants are very 

 rare, and many, that seem to be so while they are fresh, 

 gain, on drying, a very decided perfume. 



The odor of plants is due to principles very unequally 

 distributed throughout their different organs ; some solid, 

 as resins and balsams ; others which are liquid, and known 



