Castration, a surgical operation practised upon some of the domestic animals, which consists in taking away the necessary and essential organs of reproduction, namely, the testicles in the male or the ovaries in the female. When performed upon the female, the operation is more commonly known as spaying. The object to be accomplished in either case is to moderate the impetuosity of the animals, to render them more docile and submissive, or more adapted to the kind of labor required of them, to increase their size, or to dispose the system to the accumulation of fat. The advantages which it sometimes confers in these respects are, however, often more than counterbalanced by other effects. Thus it undoubtedly diminishes the activity, the courage, the endurance, and even the intelligence, or at least the quickness of its manifestation. It is not therefore an operation to be performed on all animals, even of the male sex, indiscriminately, but should be applied with judgment only to those cases in which it is required by the special conditions, the particular employment, or the peculiar natural disposition of the animal. Castration may be performed at all ages; but its effects are more decided if performed before than after the age of puberty.

In the first case, the animal never arrives at the usual fully developed adult condition, and, if of the male sex, does not acquire the external marks which distinguish him from the female, nor the general masculine bodily contour. On the other hand, if these sexual characters have already been developed, they do not disappear on castration, and the animal simply loses the power of reproducing Ids species. (See Eunuch.)