Jak szczekają nasze psy na wschodniej granicy Polski: po rusku czy po polsku?

The text is devoted to the verb brechać, brzechać “bark” which is one of many examples of an overlap between Polish and East Slavonic systemic features, difficult to classify as native or foreign. The analysis of numerous sources and research papers enables to conclude that both Ruthenian brechać (expansive form that influenced derivatives) and Polish brzechać occured on Polish-East Slavonic borderland. This small difference has been either ignored or interpreted incorrectly in previous research.