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 that such right is in truth only a personal obligation. For example, a personal obligation can be enforced only against the obligor and his representatives; but an equitable obligation will follow the res which is the subject of the obligation, and be enforced against any person into whose hands the res may come, until it reaches a purchaser for value and without notice. In other words, equity imposes the obligation, not only upon the person who owned the res when the obligation arose, but upon all persons into whose hands it afterward comes, subject to the qualification just stated. But the moment it reaches a purchaser for value and without notice, equity stops short; for otherwise it would convert the personal obligation into a real obligation, or into ownership. Why is it, then, that equity admits as an absolute limitation upon its jurisdiction a principle or rule which it yet seems always to be struggling against, namely, that equity acts only against the person,—æquitas agit in personam? One reason is (as has already appeared) that equity has no choice or option as to admitting this limitation upon its jurisdiction. Another reason is that if equitable rights were rights in rem, they would follow the res into the hands of a purchaser for value and without notice; a result which would not only be intolerable to those for whose benefit equity exists, but would be especially abhorrent to equity itself. Upon the whole, it may be said that equity could not create rights in rem if it would, and that it would not if it could.

The Roman pignus and hypotheca were rights in rem. The pignus was admitted into our law because it affected chattels only, and because it could not be effected without delivery of possession; but the hypotheca was rejected because it affected