Book II. ANIMAL CHEMISTRY. 291 



of it. It appears likewise as a constituent of bone and shell ; and there are few of 

 the fluid or soft parts of animals in which it does not exist in abundance. What has 

 iiitherto been termed the Resin of Bile is, according to Berzelius, analogous to albumen. 



1940. Albu7nen is extensively used in the arts. When spread thin on any substance, it soon dries, and 

 forms a coating of varnish. Its adhesive power is likewise considerable. When rubbed on leather, it 

 increases its suppleness. But its chief use is in clarifying liquors. For this purpose, any substance 

 abounding in albumen, as the white of eggs, or the serum of blood, is mixed with the liquid, and the 

 whole heated to near the boiling point. The albumen coagulates, and falls to the bottom, carrying along 

 with it the impurities which were suspended in the fluid, and which rendered it muddy. If the liquor 

 contains alcohol, the application of heat is unnecessary. 



1941. Fibrin exists in the blood, and was formerly called the fibrous part of the 

 blood. It likewise exists in all muscles, forming the essential part, or basis, of these 

 organs. It exhibits many remarkable varieties, as it appears in the flesh of quadrupeds, 

 birds, and fishes ; but has not hitherto been turned to any particular use. 



1 942. Extractive exists in the muscles of animals, in the blood, and in the brain. It 

 communicates the peculiar flavour of meat to soups. In the opinion of Foiu"croy, the 

 brown crust of roasted meat consists of it. 



1943. The soft parts of animals are constituted of these four substances, which also enter 

 into the composition of the hard parts and of the fluids. They are readily distinguishable 

 from one another- Extractive alone is soluble in alcohol ; gelatine is insoluble in cold, 

 but soluble in hot, water ; albumen is soluble in cold, and insoluble in hot, water ; the 

 fibrin is equally insoluble in hot and cold water. They are variously mixed or united ; 

 and as they consist of some elementary principles, chiefly carbon, hydrogen, oxygen, and 

 azote, it is probable that they are in many cases changed, the one into the other, 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. 



1944. Muciis 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 of the urine ; 

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

 any suspended particles like the blood, but is homogeneous. {Dr. Young, Annals of Phil, t 

 vol. ii. p. 117.) When inspissated, it constitutes, in the opinion of some, the basis of the 

 epidermis, horns, nails, and 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. 



1 945. Urea is a substance obtained by evaporation and trituration frcan 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. 



1946. Sugar exists in considerable abundance in milk, and in the urine of persons 

 labouring 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, however, it exists 

 as a constituent principle, and may readily be obtained by the following process : evapo- 

 rate 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. 



1 947. Oils 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, ambergris, fat, and common oils. 



1948. 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. 



1949. Ambergris 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 

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



1950. 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. 



1951. Tallow is the fat of ruminating animals, and is hard and brittle j 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 oint- 

 ments, and to diminish friction, are well known. 



1952. The properties of oils depend in a great degree on the mode of preparation, with the exception of 

 the odour, 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 procured 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 



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