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CHAPTER IX.

ANIMAL FIBRES. THICKENINGS Of ANIMAL ORIGIN.

'T'HE classification of fibres according to their origin is important in ascientific point of view, as it is based upon a difference of chemicalcomposition. A similar link of connection exists between wool and silk asthere does between hemp, flax, and cotton, the latter being intimately alliedto the neutral carbo-hydrates, while silk and wool belong to the nitrogenousalbumenoid substances, which sometimes contain sulphur as well as nitrogen.

We are here led by analogy to the consideration of albumen, caseine, gluten,fibrine, and gelatine, all of which now play an important part in the fixing ofcolouring matter and pigments to woven tissues.

Albumenoid Substances.

These are very widely dispersed both in the vegetable and animalkingdoms, though they are often considered to belong chiefly to thelatter. The number of these bodies is very large, but their characteristicdifferences are not great. The chief substances of this kind which demandattention in this work are albumen, fibrine, gluten, and caseine, to whichis often added the diastase of malt, diastase being the name given to albumenin that state in which it effects the conversion of starch into dextrine andcellulose. The plastic substances of the animal organism, as, for instance,that membranous secretion called wool, the fibroine of silk, gelatine, and thetissues which yield gelatine, on being boiled in water, are in some respectssimilar to the albumenoid substances; they differ from them, however,sufficiently to admit of a separate classification.

The following table exhibits the composition of the most prominent of thesesubstances, many of which are only molecular modifications of each other:—

Albumen, Fibrine,Caseine.

Epidermic

Produ&ions.

Gelatine yieldingTissues.

Fibroine.

Carbon

•* 53*5

50-6

49’38

5°'5

Hydrogen ..

.. 7-1

TO

6-51

7'°

Nitrogen ..

.. i 5 -8

T 7'5

I 7 - 6 o

i8-o

Oxygen

.. ig'8

226

26'50

2 4'5

Sulphur

.. i-8

2'3

O’OO

o-o

The albumenoid substances are generally solid, and not capable of assuminga crystalline shape: the protein substance of the blood globules has occasionallybeen seen in a crystalline state. As to their solubility in water, this seemsl o depend entirely upon certain salts or acids with which they are combined ;