4e. The Pineal Body

The pineal body (epiphysis) is a small reddish-gray body, about 8 mm. in length which lies in the depression between the superior colliculi. It is attached to the roof of the third ventricle near its junction with the mid-brain. It develops as an outgrowth from the third ventricle of the brain. 1 In early life it has a glandular structure which reaches its greatest development at about the seventh year. Later, especially after puberty, the glandular tissue gradually disappears and is replaced by connective tissue. 2 Structure.—The pineal body is destitute of nervous substance, and consists of follicles lined by epithelium and enveloped by connective tissue. These follicles contain a variable quantity of gritty material, composed of phosphate and carbonate of calcium, phosphate of magnesium and ammonia, and a little animal matter. 3 It contains a substance which if injected intravenously causes fall of blood-pressure. It seems probable that the gland furnishes an internal secretion in children that inhibits the development of the reproductive glands since the invasion of the gland in children, by pathological growths which practically destroy the glandular tissue, results in accelerated development of the sexual organs, increased growth of the skeleton and precocious mentality. 4

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