Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 CUTANEOUS GLANDS. 77 tubule, into which projects the glomerulus (fig. 72). coil of arterial blood vessels known as Yery generally tlie outer body surface is the seat of special secre- tions which frequently play an impor- tant part in the economy of the animal, and are used especially as a means of protection and defence. The same is true also of the secretions of the accessory glands opening into the anterior or posterior end of the al
Elementary text-book of zoology, general Elementary text-book of zoology, general part and special part: protozoa to insecta elementarytextbo00clau Year: 1892 CUTANEOUS GLANDS. 77 tubule, into which projects the glomerulus (fig. 72). coil of arterial blood vessels known as Yery generally tlie outer body surface is the seat of special secre- tions which frequently play an impor- tant part in the economy of the animal, and are used especially as a means of protection and defence. The same is true also of the secretions of the accessory glands opening into the anterior or posterior end of the ali- mentary canal (salivary glands, poison glands, anal glands) (fig. 73). To the class of cutaneous glands belong, in the first place, the sweat- glands and the sebaceous glands of Mammalia. The fluid secretion of the former, on account of the ease with which it is evaporated, is of special use in keeping the body cool, while that of the latter keeps the integument and Pig. 71.—Diagrammatic represen- tation of the kidney (segmental organs) of a dog-fisli embryo (after C. Semper). Wtr, ciliated funnels ; Ug, kidney duct. its special coveringsoft and supple. The coccygeal glands of water- birds are derived from an aggre- gation of sebaceous glands; their secretion by keeping the feathers oiled preserves them from becom- ing saturated with water during swimming. The unicellular and multicell- ular integumentary glands, which are found so widely present in Insects, belong, for the most part, to the category of oil and fat glands. Aggregations of cells whose function is to secrete calcareous matters and pigment are especially ^videly present in the integu- ment of the Mollusca, and serve for the building up of the beautifully
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