CHEMISTRY OF ANIMAL SUBSTANCES.

347

Nails of animals, Mr. Hatchett has shown, are chiefly com-posed of a membranous substance, resembling coagulated al-bumen.

Horns and Hoofs of animals greatly resemble the former inall their properties.

Hair, according to Bertholet, yielded carbonate of ammonia,charcoal, nitrogen, and sulphur.

Feathers yield nearly the same products as hair. Mr.Hatchett has proved that the quill is chiefly composed of coagu-lated albumen.

Shells, or the crustaceous coverings of certain animals, suchas echini, lobsters, crabs, cray-fish, &c. and also the shells ofeggs greatly resemble bones in their composition, but the pro-, portion of the carbonate of lime they contain far exceeds that ofthe phosphate. Mother of pearl is composed, according toHatchett, of carbonate of lime and membrane. Fish scales arecomposed of membrane and phosphate of lime.

Blood is concrescible by repose and cold, and coagulable byheat. It separates into two different parts by rest. The cause ofthis spontaneous separation is unknown. The white part is calledthe serum, the other coloured part is denominated the crassa-mentum, or clot. The serum consists of albumen, gelatine,carbonate, muriate, and phosphate of soda, phosphate of lime,and sulphur. The crassamentum contains albumen, soda and sub-phosphate of iron. When blood, the moment it is drawn froman animal, is strongly agitated with a stick or other substance, awhite, solid, elastic matter separates, called fibrin, or animalgluten. It contains more nitrogen than any of the former part*of the blood.