When it is possible to choose the season most favorable for the operation, and for securing the best chances of recovery, the spring, or the early stages of the fall, are those to which the operator should give the preference, provided the atmospheric temperature is moderate and not susceptible to sudden variations. It is to be remembered that at some periods of the year, without any known or apparent cause, a tendency appears in wounds to take on gangrenous or septicemic complications which are not so generally observed in the mild weather of spring and early fall. Another essential condition which surgeons will do well to take into consideration is the general health of the subject, as in all cases of surgical interference, any diseased tendency already existing (perhaps latent) in the patient, such as an anæmic condition, a gourmy predisposition, or typhoid susceptibility are likely to give rise to the development of serious and perhaps fatal sequelæ to an operation which, simple as it may be in itself, is nevertheless not without danger, or of possible complications of its own. PREPARATIONS. The preparations to which the animal is to be subjected previous to undergoing the operation are the same as those which are required in other cases of surgical manipulation. Some portions of the preparations are, perhaps, of even greater importance, and may not, on any account, be overlooked, when we take into consideration the peculiar position in which the animal must frequently be secured in order effectually to control his movements. Hence, a low diet for twenty-four hours preceding that appointed for the operation, and an empty stomach at the time of castration, with a thorough washing of the sheath, are precautions which no surgeon entitled to the name will overlook or neglect, especially when a soliped is to be subjected to the knife. We shall discuss hereafter the indications in the case of the castration of large females. RESTRAINT. Two modes of restraint are employed in securing the animals during the manipulations for the removal of the testicles, one which is applied to all the various methods yet to be described, and the other applicable principally to the method of amputation of the cord by the use of the _écraseur_. In the former, the animal is thrown down and secured with one of his hind legs fixed in a position in which the inguinal region is fully exposed. In the latter he is allowed to remain in a standing posture, and is kept quiet by the application of a twitch upon his upper lip. As the first mode of securing the patient is the safest for all parties engaged in the undertaking, and from the further fact of its applicability in all methods of operating, we shall first consider it somewhat in detail. [Illustration: FIG. 1. Condition of the horse in lying posture. Steps to bring one of the hind legs upon the corresponding front one.]