Outlines of human physiology; designed for the use of the higher classes in common schools . closelymucus; but this cannot be known with certainty, as itis impossible to obtain them separate. Some of thesefollicles exist on the tongue, and the small openingsthat are seen on the tonsils or almonds of the ears,which are situated in the back of the throat, are sup-posed to be the outlets for the secreted fluids of thesesmall organs. 3d. Of the Glands. Glands are bodies of varioussize, more or less of a rounded form, situated in various 100 SECRETION. parts of the body. They secrete substances of
Outlines of human physiology; designed for the use of the higher classes in common schools . closelymucus; but this cannot be known with certainty, as itis impossible to obtain them separate. Some of thesefollicles exist on the tongue, and the small openingsthat are seen on the tonsils or almonds of the ears,which are situated in the back of the throat, are sup-posed to be the outlets for the secreted fluids of thesesmall organs. 3d. Of the Glands. Glands are bodies of varioussize, more or less of a rounded form, situated in various 100 SECRETION. parts of the body. They secrete substances of verydifferent character, and, in some instances, having littleor no resemblance to the blood from which they se-crete them. In the more perfect glands there is foundone or more arteries, which carry the blood to. thisorgan, a set of veins, which return a portion of it, andanother set of vessels, which usually unite in a commontrunk called an excretory duct, which conveys the fluidformed by the gland to its place of destination. Theintimate nature of the glandular structure is wholly un-. A Gland with an excretory duct, a a The sub-stance of i he gland irregular and lobulaled. bbThe small branches, by which the excretory ductarises from the gland, c i he trunk of the excre-tory duct fully formed. known, and it is by no means determined whether thesecretion is performed by this structure, or whether itis dependent on the action of the vessels alone. Insome instances, where the secreted fluid differs verymaterially from the blood, the secretory apparatus issimple; while in other cases, in which it bears a closeresemblance to the fluid from which it is separated, theorgan by which it is effected is of a complicated char- SECRETION. 101 lacter. It is probably impossible to settle a question ofthis kind by actual experiment. The glands, as has been observed, are of very varioussize. The lachrymal gland, which secretes the tears,is a flat body, not larger than a small almond, while th
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