Practically, the knowledge obtained dictates in a most emphatic manner that every stock-grower use his utmost endeavor to obtain the services of the best sires; that is, the best for the ends and purposes in view--that he depend chiefly on the sire for outward form and symmetry--and that he select dams best calculated to develop the good qualities of the male, depending chiefly upon these for freedom, from internal disease, for hardihood and constitution, and, generally, for all qualities dependent upon the vital or nutritive system. The neglect of the qualities of the dam, which is far too common--miserably old and inferior animals being often employed--cannot be too strongly censured. With regard to the laws which regulate the sex of the progeny very little is known. Many and extensive observations have been made, without reaching any definite conclusion. Nature seems to have provided that the number of each sex; produced, shall be nearly equal; but by what means this result is attained, has not as yet been discovered. It has long been a disputed point, whether the system of _breeding in-and-in_, or the opposite one of frequent crossing, has the greater tendency to improve the character of stock This term, in-and-in, is often very loosely used and as variously understood. Some confine the phrase to the coupling of those of exactly the same blood, as brothers and sisters, while others include in it breeding from parents and offsprings; and others still employ it to embrace those of a more distant relationship. For the last, the term breeding-in, or close breeding, is generally deemed more suitable. The current opinion is decidedly against the practice of breeding from any near relatives; it being usually found that degeneracy follows, and often to a serious degree; but it is not proved that this degeneracy, although very common and even usual, is yet a necessary consequence. That ill effects follow, in a majority of cases, is not to be doubted; but this is easily and sufficiently accounted for upon quite other grounds. Perhaps, however, the following propositions may be safely stated: That in general practice, with the grades and mixed animals common in the country, _close-breeding should be scrupulously avoided_ as highly detrimental. It is better _always_ to avoid breeding from near relatives whenever stock-getters of the same breed and of equal merit can be obtained which are not related. Yet, where this is not possible, or where there is some desirable and clearly defined purpose in view--as the fixing and perpetuating of some valuable quality in a particular animal not common to the breed--and the breeder possesses the knowledge and skill needful to accomplish his purpose, and the animals are perfect in health and development, close breeding may be practised with advantage.