ed flow of livestock from the ranges and
farms of the West and Southwest through the great stockyards and
slaughtering centers on the borders of that region, and thence in the
form of meat products to the consuming cities of the country in the
Middle West and East, or, still as livestock, to the feeding places and
fattening farms in the Middle West or East for further preparation for
the market."[433] The stockyards, therefore, were "not a place of rest
or final destination." They were "but a throat through which the current
flows," and the sales there were not merely local transactions. "They do
not stop the flow;--but, on the contrary" are "indispensable to its
continuity."[434]

In Chicago Board of Trade _v._ Olsen,[435] involving the Grain Futures
Act, the same course of reasoning was repeated. Speaking of the Swift
Case, Chief Justice Taft remarked: "That case was a milestone in the
interpretation of the commerce clause of the Constitution. It
recognized the great changes and development in the business of this
vast country and drew again the dividing line between interstate and
intrastate commerce where the Constitution intended it to be. It refused
to permit local incidents of a great interstate movement, which taken
alone were intrastate, to characterize the movement as such."[436] Of
special significance, however, is the part of the opinion which was
devoted to showing the relation between future sales and cash sales, and
hence the effect of the former upon the interstate grain trade. The
test, said the Chief Justice, was furnished by the question of price.
"The question of price dominates trade between the States. Sales of an
article which affect the country-wide price of the article directly
affect the country-wide commerce in it."[437] Thus a practice which
demonstrably affects prices would also affect interstate trade
"directly," and so, even though local in itself, would fall within the
regulatory power of Congress. In the following passage, indeed, Chief
Justice Taft whittles down, in both cases, the "direct-indirect" formula
to the vanishing point: "Whatever amounts to more or less constant
practice, and threatens to obstruct or unduly to burden the freedom of
interstate commerce is within the regulatory power of Congress under the
commerce clause, and it is primarily for Congress to consider and decide
the fact of the danger and meet it. This court will certainly not
substitute its judgment for that of