Professor Keener says that the obligation must be one which is imposed "because of the interest which the public has in its performance." 1 This seems too broad, since it includes, apparently, any obligation the breach of which constitutes a criminal offense. If, for instance, every citizen were required by the tax law to file a statement of all property owned by him and it were made a misdemeanor to neglect so to do, the public would be interested, in a sense, in the performance of this obligation; yet it is improbable that a person who performed the duty for another without authority would under any circumstances be permitted to recover the value of his service. The true limitation, it is believed, is that the obligation must be such that actual and prompt performance of it as distinguished from the payment of a penalty for non-performance, is a matter of grave public concern. The obligation of a man to support his wife is perhaps the best example that can be given. The moral sense of the community requires that such an obligation be actually performed; the imposition of a penalty for its non-performance is not enough. If, therefore, the person upon whom the obligation rests fails to perform it, intervention is clearly a duty.

1 ."Quasi-Contracts," p. 341. 310