By crossing the blood we undiTstand the scleotion of a sire oomposed wholly of different blood fVom that of the dam, or as different as oan be obtained of such quality as is suitable to the particular purpose in view. Tiras, in binding race horsea, it is i'ound that oontinuing in thn same strain beyond two stupes deteüorates the constitutional health, dixuinishes the bone, and lowers thehtight; henee it is important to ivoid tïiis evil, and snother strain must be aelootecl which shall lead to the sume resulta which were previously in existen ce, without the above deterioration ; and tliis is t.rmed out-crossing, or, inoie comuionly, ciossiug. ïhe great difficulty is to obtai i this object without destroying the haimony of propoitious, aml due subordina tion of one part to anothei', which is ntiessary for the race horse, and without wh c'i he seldom obtains high speed. lenost every individual breed has peculiar characteristics, and so long as the si e und dam are both in possrbsion ol' them, they will continue to reappear in the produce; but if a dam possessintr them is put to a horse of a different chiiracter, the result is often that the produce is uot a medium between the two, bnt is in its ai tarior paris like its dam, and in ite poFt-rior resemblling its sire, nr vioe versa, thiin which no more un fortúnate result can occur. Thus, vc will suppose that a very strong, mnscnlftr horsc is ]ut to a, light racingmaie: instead oí the produce being moderatply stout 11 over, hp will often be very stout and strong 1 ehind, nd very light and weak befnre, ni, as a consequence, liis hind-quarters wli tire his foro lirabs, by ffiving theiu inore to do tban they have the power of acuomplishiug.