x INTRODUCTION. 
perfection is in a great measure attributable to their mode of 
living ; hunting and war are their chief pursuits, to which they 
are trained from their earliest childhood, and, although often 
subject to privation, their hardy vigorous life in the free air is 
healthful in the highest degree; their physical faculties are 
developed by constant practice. The senses of sight and hearing 
in these wanderers are as singularly perfect as their sense of 
scent. Such perfection is quite unknown to dwellers in cities, 
whose physical faculties are deteriorated by luxurious habits of 
civilization, idleness, sedentary toil, disease, and other causes and 
curses, 
The organic compound mercaptan above referred to is intensely 
powerful in odour, otherwise it could not be perceived by such 
minute molecules of its vapour. Although a laboratory product, 
it occurs in nature in the plant Allium ursinum, a species of onion. 
In small quantities the flavour of onions is pleasant, but the odour, 
even in very small quantities, is to most people unpleasant. 
The Allium ursinum, sometimes called “‘ Ramson’s garlic,” is 
frequently found in shady meadows; it diffuses when in flower an 
odour of garlic, and imparts this flavour to the milk of the cows 
that feed upon it. This odour, occurring in different degrees of 
strength in most alliaceous plants, appears to be mainly due to the 
presence of a sulphide of allyl, the principal constituent of essen- 
tial oil of garlic. The difference between oil of garlic and oil of 
asafoetida seems to be that the plant furnishing this last contains 
a larger proportion of sulphur, consequently develops the odorous 
principle in a more offensive degree. A number of plants belong- 
ing to the genus Ferula possess an alliaceous odour ; it is most 
intense in the Ferula fetidissima (Regel), which also secretes 
more asafcetida than any other asafcetida plant. The Scorodosma 
fetida, a gigantic umbelliferous plant found in the sandy Steppes 
east of the Caspian, and closely allied to the Ferula, is also said to 
furnish a sort of gum asafcetida. On cutting into the upper part 
of the root a juice exudes, which hardens by exposure. Persians 
and other Asiatics use it as a condiment; they even call it “ the 
