COCCYGEAL 

BODY This is a small median body, about the size of a pea, situated in front of the apex of the coccyx and between the insertions of the levatores ani muscles . It resembles the carotid body in its microscopical structure, but is not so vascular . Concentric corpuscles, like those of the thymus, have been recorded in it . It derives its arteries from the middle sacral and its nerves from the sympathetic . Of its embryology and comparative anatomy little is known, though J . W . Thomson Walker has recently shown that numerous, outlying, minute masses of the same structure lie along the course of the middle sacral artery (Archie f. mikroscop . Anat . Bd. lxiv.) . The probability is that, like the carotid body, it is sympathetic in origin . (Quain's Anatomy gives excellent illustrations of the histology of this as well as of all the other ductless glands.) For the literature on and further details concerning the foregoing structures the following works should be consulted: Quain's Anatomy,vol. i (19o8,London,Longman & Co.) ; McMurrich'sDeaelopment of the Human Body (London, Rebman, 1906); Wiedersheim's Vergleich . Anat. der Wirbeltiere (Jena, 1898) .

' (F . G .