Book II. ANIMiAL CHEMISTRY. 289 



guished from vegetables. Azote likewise occurs, in an uncomblned state, in the air-bag of some 

 fishes. 



1885. Phosphorus. Tliis inflammable body exists, in union with oxygen, in the state of phosphoric 

 acid, in many of the solids and fluids of animals. Its existence, however, in an uncombined state, has 

 not been satisfactorily determined, although there appears a tendency to refer the luminousness of se- 

 veral animals to the slow combustion of this substance. Even phosphoric acid can scarcely be said to 

 exist in a separate state, being found in combination with potash, soda, ammonia, lime, or magnesia. 



1886. Sulphur, in combination, exists in considerable abundance in animal substances. It can scarcely 

 be said to occur in a separate state in animals ; at least the experiments which may be quoted as encour- 

 aging such a supposition, are by no means decisive. United with oxygen, in the form of sulphuric acid, 

 it exists in comljination with potash, soda, and lime. 



1887. Fluoric acid has been detected in bones and urine, in a state of combination with lime. 



1888. Muriatic acid exists in a great number of the animal fluids, in combination with an alkali, as in 

 the ammonia and soda of urine. 



1889. Iodine has been detected in sponge. 



1890. Potash exists in combination with the sulphuric, muriatic, or phosphoric acids ; but it is far from 

 abundant in animal fluids. 



1891. Soda is present in all the fluids in various states of combination, and is more abundant than the 

 preceding. It gives to many of the secretions the alkaline property of changing vegetable blues into 

 green. It is found in union with the carbonic, phosphoric, sulphuric, and muriatic acids. 



1892. Ammonia exists in its elements in all the fluids, and many of the solids of animals, and is fre- 

 quently produced during putrefaction. These elements are likewise found united in the system, and the 

 alkali then appears in union with the various acids, as the phosphoric, muriatic, and lactic. 



1893. Lw^, of which the hard parts of animals, such as bones and shells, are chiefly composed, is of 

 universal occurrence. It is always in a state of combination^ and chiefly with the carbonic or phosphoric 

 acids. 



1894. Magnesia occurs sparingly. It has been detected in the bones, blood, and some other substances, 

 but always in small quantity, and chiefly in union with phosphoric acid. 



189a. Silica occurs more sparingly than the preceding. It is found in the hair, urine, and urinary 

 calculi. 



1896. Iron has hitherto only been detected in the coloring matter of the blood, in bile, and in milk. Its 

 peculiar state of combination in the blood has given rise to various conjectures ; but a satisfactory solu- 

 tion of the question has not yet been obtained. In milk, it appears to be in the state of phosphate. 



1897, Manganese, in oxide, has been observed, along with iron, in the ashes of hair. 



1898. Such are the simple substances which have been detected by chemists in the 

 solids and fluids of animals ; but seldom in a free state, and often in such various pro- 

 portions of combination as renders it extremely diflScult to determine their true 

 condition. 



1899. The compounds of organization are gelatine, albumen, fibrin, mucus, urea, 

 sugar, oils, and acids. 



1900. Gelatine occurs in nearly a pure state in the air-bags of different kinds of fishes, as, for example, 

 isinglass, dissolved in hot water and allowed to cool, forms jelly. When a solution of tannin is dropped 

 into a solution of gelatine, an union takes place, and an insoluble precipitate of a whitish color falls to the 

 bottom. It is on the union of the tannin of the oak bark with the gelatine of the hides, that the process 

 of tanning leather depends. Gelatine exists in abundance in different parts of animals, as bones, muscles, 

 skin, ligaments, membranes, and blood. It is obtained from these substances, by boiling them in 

 warm water ; removing the impurities, by skimming, as they rise to the sufface ; or by subsequent 

 straining and clarifying. It is then boiled to a proper consistency. It is the characteristic ingredient of 

 the softest and most flexible parts of animals. 



1901. Gelatine is extensively used in the arts, under the names of glue and size, on account of its adhesive 

 quality, and to give the requisite stiffness to certain articles of manufacture. In domestic economy, it is 

 likewise employed in the form of jelly, and in the formation of various kinds of soup. "What is termed 

 Portable Soup is merely jelly which has been dried, having been previously seasoned, according to the 

 taste, with different spices. 



1 902. Albumen, the white of an egg, exists in great abundance, both in a coagulated 

 and liquid state, in the different parts of animals. Hair, nails, and horn, are composed 

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

 the fluid or soft part of animals, in which it does not exist in abundance ; what has 

 hitherto been termed the Resin of Bile, is, according to Berzelius, analogous to 

 albumen. 



1903. Albumen is extensively used in the arts. When spread thin on any body, 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. 



1904. 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. 



1905. Extractive exists in the muscles of animals, in the blood and in the brain. 

 It communicates the peculiar flavor of meat to soups. In the opinion of Fourcroy^ 

 the brown crust of roasted meat consists of it. 



1 906. 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, 



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