[perh. some corruption of CASTANE, or L. castanea chestnut, in F. chataigne.] (See quot. and cf. CHESTNUT.)
1888. Brit. Med. Jrnl., 25 Feb., 413/1. The singular patch of hard integument known as the castor on the inside of the foreleg of the horse.
1888. Veterinarian, May, 304. Another organ in process of disappearance is that piece of horn inside the fore-arm, where it is termed the chestnut, and that inside the hock, where it is termed the castor; it corresponds to the finger nail of the thumb of our hand, and of the foot of the five-toed ancestor of the horse.
Castor5. Min. See CASTORITE.
