But it alarmed the South. By the Southerners of the more radical pro-slavery school it was accepted as a notice to quit; a notification that so far as Northern anti-slavery sentiment could control the matter, there was to be no further addition of a single acre to the slave territory of the Union; that so far as that sentiment could influence national politics, the power of the Federal Government was thenceforth and forever to be exercised to prevent the extension of slavery into any new territory acquired or to be acquired by the Union north or south of the Missouri Compromise line, and in the end to abolish the system altogether. Let us clearly understand this situation. The Wilmot Proviso and all the attempted legislation, by which it was sought to confine slavery within the boundaries prescribed for it by existing conditions, seemed to the opponents of slavery merely a legitimate effort to emphasize the fact that free labor was national, while slavery was a permitted evil within prescribed limits permitted solely because within those limits the national power was not authorized to exert itself for the extermination of the system. On the other hand, all these things seemed to the Southern mind to be an utterly unjust discrimination against a part of the people. The territories involved in the controversy had become national possessions, they contended, largely through the activities of Southern men and Southern statesmanship. It was felt to be a grievous wrong that Southern men should be forbidden to emigrate to those territories on equal terms with other citizens of the Union or that thus emigrating they should be forbidden to take with them their slave property, which represented in part their industrial system but in far greater part their domestic life. The very proposal thus to exclude them from an equal participation in the opportunities and the privileges opened to other citizens of the Republic by the acquisition of these new territories seemed to them a threat, a notification that henceforth they were to be treated not as citizens of the Union entitled to the same protection and the same privileges that were extended to other citizens, but as inferior and offending persons, persons graciously permitted to exist, but persons to be excluded, because of their offenses, from an equal participation in the conquests and land purchases of the Nation and from the enjoyment of a share of the benefits resulting from the addition of a great and immeasurably rich territory to the national domain.