Ds are engaged in the business of buying livestock at stockyards throughout the country. Ds then slaughter such livestock at their respective plants in places named, in different States, and convert the live-stock into fresh meat for human consumption. Ds then sell such fresh meats to dealers and consumers in different States. Ds then ship the same meats, when so sold from the said places of their preparation, over the several lines of transportation of the several railroad companies serving the same as common carriers. It was alleged that Ds made agreements amongst themselves to refrain from bidding against each other. Ds also agreed to bid up, through their agents, the prices of livestock for a few days at a time, 'so that the market reports will show prices much higher than the state of the trade will warrant,' thereby inducing stock owners in other States to make large shipments to the stockyards to their disadvantage. This scheme is effected by secret periodical meetings where they fix prices to be enforced until changed at a subsequent meeting. They impose penalties for deviations and notify one another of the delinquencies of such errant dealers and keeping a blacklist of delinquents, and refusing to sell meats to them. They also colluded to get less than lawful rates from the railroads to the exclusion of competitors. The United States (P) sued Ds for violating the Sherman Antitrust Act of 1890. Ds demurred to the bill itself and also argued that the agreements did not affect interstate commerce and was, therefore, not subject to the Act. Ds appealed from an injunction granted. The Supreme Court granted certiorari.