Knox & Crawford v. Summers and Thomas, 3 Cranch 496

The Court were unanimously of opinion, that the appearance by attorney cured all irregularity of process. The defendant, perhaps, might have appeared in propria personó,, and directly pleaded in abatement. But having once appeared by attorney, he is precluded from taking advantage of the irregularity. The judgment reversed, the defendant ordered to answer over, and the cause remanded for further proceedings.