Every one is familiar with the words in which the Constitution, while not naming Slavery, recognizes, under a certain phase, its existence, and aids it, under certain circumstances, to maintain the rights to involuntary labor which, under State laws, it claims; thus:-- "No person held to service or labor in one State, under the laws thereof, escaping into another, shall, in consequence of any law or regulation therein, be discharged from such service or labor, but shall be delivered up on claim of the party to whom such service or labor may be due." The claims to service or labor here referred to may be for years or for life: both are included in the above provision. In point of fact, there were existing, at the time that provision was adopted, (as there still exist,) both classes: the first class, for a term of years, then consisting, in part, of claims against foreign adults who had bound themselves to service for a limited time to repay the expenses of their emigration,--but chiefly, as now, of claims to the service or labor of what were called apprentices, usually white minors; the second, for life, were claims to the service or labor of men, women, and children of all ages, exclusively of African descent, who were called slaves. The first class of claims were found chiefly in Northern States; the second chiefly in Southern. There was a great disparity between the numbers of the two classes. While the claims to service or labor for years numbered but a few thousands, there were then held to service or labor for life upwards of six hundred thousand persons: and the number has since increased to about four millions. The constitutional provision is, that persons from whom under State laws service or labor is due shall not be exonerated from the performance of the same by escaping to another State. The apprentice, or the slave, shall, in that case, on demand of the proper claimant, be delivered up. Such a provision clearly involves the recognition of certain rights of property; but of what kind? Is the ownership of one human being by another here involved? Is the apprentice, or the slave, recognized in this clause as an article of merchandise?