290 SCIENCE OF AGRICULTURE. Part IL 



hydrogen, oxygen, and azote, it is probable that they are changed, the one into the other, 

 in many eases by the living principle, a transmutation which the chemist has succeeded 

 in accomplishing, and which may soon be of advantage in the arts. The proportion of 

 carbon appears to be least in gelatine and greatest in fibrin. 



1907. Mucus occurs in a liquid state in the animal economy, as a protecting covering 

 to different organs. It necessarily differs in its qualities, according to the purposes it is 

 destined to serve. In the nose it defends the organ of smell from the drying influence 

 of the air, in the bladder, it protects the interior from the contact of the acid urine, 

 while it preserves the gall-bladder from the action of alkaline bile. It does not 

 contain any suspended particles Hke the blood, but is homogeneous. (Dr. Youngs 

 Annals of Phil. ii. p. 117.) When inspissated, it constitutes, in the opinion of some, 

 the basis of the epidermis, horns, nails, feathers. But the difficulty of obtaining it in 

 a pure state, and the discordant characters assigned to it by different chemists, prevent 

 us from reposing confidence in the accuracy of the analysis of those substances, of 

 which it is considered as forming an essential ingredient. 



1908. Urea is a substance obtained by evaporation and trituration from the urine of 

 the mammalia when in a state of health. In the human subject it is less abundant 

 after a meal, and nearly disappears in the disease called diabetes, and in affections of 

 the liver. 



1909. Sugar exists in considerable abundance in milk, and in the urine of persons 

 laboring under diabetes. In the latter fluid, it is to be considered as a morbid 

 secretion of the kidneys, occupying the natural situation of the urea. In milk, how- 

 ever, it exists as a constituent principle, and may readily be obtained by the following 

 process : evaporate fresh whey to the consistence of honey, dissolve it in water, clarify 

 with the whites of eggs, and again evaporate to the consistence of syrup. On cooling, 

 white cubical crystals will be obtained, but less sweet than vegetable sugar. 



1910. Oi/s vary greatly as to colour, consistence, smell and other characters. They 

 possess, however, in common, the properties of the fixed oils, in being liquid, either 

 naturally or when exposed to a gentle heat, insoluble in water and alcohol, leaving a 

 greasy stain upon paper, and being highly combustible. They are distinguished as 

 spermaceti, ambergrease, fat, and common oils. 



1911. Spermaceti constitutes the principal part of the brain of the whale, and is freed from the oil which 

 accompanies it, by draining and squeezing, and afterwards, by the employment of an alkaline lie, which 

 saponifies the remainder. It is then washed in water, cut into thin pieces with a wooden knife, and 

 exposed to the air to dry. It is used in medicine and candlemaking. 



1912. Ambergrease is found in the intestines of the spermaceti whale, and in those only which are in a 

 sickly state. It appears to be the excrement, altered by a long retention in the intestines, and therefore 

 scarcely merits a place among the natural ingredients of the animal system. Upon being voided by the 

 animal, it floats on the surface of the sea, and has been found in various quarters of the globe. It usually 

 contains the beaks of cuttle fish adhering to it. It is employed in small quantities by druggists and 

 perfumers. 



1913. Fat consists of two substances, suet and oil. It is usually purified by separating the vessels and 

 membranes which adhere to it, by repeatedly washing with cold water, and afterwards melting it, along 

 with boiling water. 



1914. Tallow is the fat of ruminating animals, and is hard and brittle, while the fat of the hog, called 

 lard, is soft and semifluid. Its uses as an article of food, in the making of candles, hard soap, and 

 ointments, and to diminish friction, are well known. 



1915. The properties qf oils depends in a great degree on the mode of preparation, with the exception of 

 the odor, which arises from the kind of animal from which the oil has been derived. Spermaceti oil is 

 considered as the thinnest of the animal oils, and the fittest for burning in lamps. It is obtained from the 

 spermaceti, by draining and pressure. Train oil is prooured by melting the blubber, or external layer of 

 fat, found underneath the skin of different kinds of whales and seals. From the process employed, it 

 contains, besides the oil, gelatine, albumen, and other animal matters, which render it thick, dark-' 

 colored, and disposed to become rancid. Fish oil is sometimes extracted from the entire fish, (as the 

 sprat, pilchard, and herring, when they occur in too great quantities to be salted) by boiling in water, and 

 skimming off the oil, as it appears on the surface. In general, however, the oil is obtained from the livers 

 of fish, in which it is lodged in cells. 



1916. The acids found in animals consist of various proportions of carbon, hydrogen, 

 oxygen, and azote. Some of them are peculiar to the animal kingdom, and others exist- 

 in equal abundance in plants. 



1917. The uric or lithic acid, abounds in urine, and appears to be a production of the kidneys. The 

 lactic acid is common in the animal fluids. The amniotic acid has been found in the uterus of a cow. 

 The/ormic acid, by distilling ants. The benzoic, oxalic^ acetic, and malic acids, are common both to plants 

 and animals, but occur but seldom in the latter. 



1918. These elementary substances, by combining in different proportions, exhibit a 

 great variety of separate substances. The earthy salts are likewise abundant ; and when 

 they occur in a separate state, they strengthen the albuminous framework, and form the 

 skeleton, giving stability to the body, and acting as levers to the muscles. The alkaline 

 salts occur in the greatest abundance in the secreted fluids. 



1919. The Jiuids consist of those juices which are obtained from our food and drink, 

 such as the chyle, and are termed crude of the blood; or prepared from the crude fluids, and 

 destined to communicate to every part of the body, the nourishment which it requires, 

 and of those fluids which are separated from the blood, in the course of circulation, such 



