Page:Popular Science Monthly Volume 19.djvu/145

Rh a very complex nitrogenized compound, which thus becomes transformed into an insoluble albuminoid substance. In acute poisoning there is no time for the arseniated lecithine to be subjected to physiological reactions and be eliminated, and the animal dies under the local influence of the poison without sensible variation of the normal phosphorus of the nervous matter. In slow and chronic poisoning the replacement takes place slowly; arseniated lecithine is formed, and acts as ordinary lecithine, passing gradually into the insoluble albuminoid state, while the phosphorus is steadily diminished, giving place to the arsenic.

The Otto of Roses.—The otto of roses consists of an odoriferous liquid containing oxygen combined with a solid hydrocarbon called stearoptene, which is destitute of perfume. The quality of the oil is determined by the relative proportion of these substances, and that is dependent chiefly on conditions of climate. The Bulgarian oils contain about eighteen per cent., the oils distilled in France and England as much as thirty-five and even sixty-eight per cent. of stearoptene. The difference in the proportions is also shown in the higher temperature required to melt the oil which contains a greater relative amount of stearoptene. The Bulgarian oil melts at from 61° to 64°, French and English oils from 70° to 89°. Even in Bulgarian oil a notable difference is observed between that produced on the hills and that from the lowlands. The most important source of otto of roses is a small district in Bulgaria or East Roumelia, stretching along the southern slopes of the central Balkans, and approximately included between the twenty-fifth and twenty-sixth degrees of east longitude and the forty-second and forty-third degrees of north latitude. A suitable soil for the growth of roses is furnished, with need for but little manuring, by the decomposition of the syenite, which is the characteristic rock of the region. The average summer temperatures of the district are 86° at noon, and 68 in the evening. The rose-bushes do best on sandy slopes having a good exposure to the sun. The flowers of bushes which grow on inclined ground are much richer in oil, and that of a stronger quality, than those raised on level land, and are therefore more esteemed and dearer. The flowers when fully expanded are gathered before sunrise, often with the calyx attached, and should be treated the same day. In Bulgaria, roses which have matured slowly in moderately cold weather furnish the richest yields; in England, the contrary appears to be the case. The flowers are distilled for an hour and a half, with double their volume of water, in a copper still from which a pipe passes through a tub that is kept constantly cool by inflowing spring-water. After the distillate has been allowed to stand for a day or two at a temperature exceeding 59°, the oil is skimmed off from it. The residual liquors are used instead of spring-water for subsequent distillations. The rose-water which comes over last is extremely fragrant, and is much prized for medical and culinary purposes. Pure otto, carefully distilled, is at first colorless, but speedily becomes yellowish; has a specific gravity of about 0·87, boils at 444°, and solidifies at from 51·8° to 60·8°, or at higher temperatures in the case of inferior oils, and is soluble in absolute alcohol. It is tested by its odor, which can be judged only after long experience; its congealing-point (a good oil should congeal in five minutes at a temperature of 54·5°), and by the crystallization of the stearoptene with light, feathery, shining plates filling the whole liquid. It is sometimes adulterated with spermaceti, which may be detected by its readiness to solidify, and by other essential oils, the effect of which is sometimes to lower the congealing-point. Rose-water and otto of roses are also produced in India; in Persia, where the trade, formerly important, has nearly disappeared; in the Mediterranean countries of Africa, and in France. The otto of the Provence rose has a characteristic perfume, which arises, it is believed, from the pollen of orange-flowers, which is brought by bees to the petals of the roses.

Effects of Petting on Animals.—Mr. A. D. Bartlett, of the Zoölogical Gardens, London, has remarked that while adult carnivorous animals—lions, tigers, leopards, etc.—can seldom be tamed and then only at the cost of danger, the young become very tame and fond of those who feed and caress