The drawing of the barking dog used by Rembrandt as the model for his barking dog in The Night Watch has been identified in the collection of the Rijksmuseum. The pup is in a 1619 drawing by Adriaen van de Venne (15901662), and while there are some differences in the two designs, the dogs share a very specific head angle, expression, posture and collar, and the chalk sketch under The Night Watch exposed by Macro-XRF imagine, shows Rembrandts original design was even more similar to Van de Vennes.The original dog was discovered by researchers working on Operation Night Watch, the Rijksmuseums multi-year, multi-disciplinary project of study and conservation of Rembrandts monumental masterpiece. The drawing caught the eye of Anne Lenders, Rijksmuseum curator of 17th century Dutch paintings, when she happened upon it at an exhibition dedicated to Adriaen van de Venne, a Dutch Golden Age painter and book illustrator who was famous in Rembrandts time and continuing through the 18th century.The dog was part of frontispiece of Self-Conflict, or, The Powerful Motions Between the Flesh & Spirit Represented in the Person and upon the Occasion of Joseph when by Potiphars Wife He Was Enticed to Adultery : A Divine Poem, a popular book by poet Jacob Cats published in 1620. The drawing depicts Joseph standing center in a ray of godly light, his hands raised and his eyes looking into the light. In the background is the scene of Joseph wrenching himself away from Potiphars wifes attempt to drag him to her bed by his cloak. The dog is at central Josephs feet, his forequarters low to the ground, his head up and mouth open in a bark, the same pose of the dog in The Night Watch. The most striking similarity is the identical rotation of each dogs head, with both looking upward in the same direction, their mouths slightly open. Another matching feature is the dark line indicating the position of the right eye. In addition, the skullcap of both animals is divided into two sections, and their collars closely correspond. There are small differences, however: the nose of the dog in The Night Watch is slightly flatter, for example, and its ears hang further down. Rembrandt also made his dogs mouth slightly more open, and added a tongue.The pose of the two dogs is similar, too. As in Rembrandts painting, Van de Vennes drawing depicts the dog positioned diagonally within the picture plane, with its upper body close to the ground. The biggest difference is that the dog in The Night Watch stands on all four legs, whereas Van de Vennes lies on its front legs, with its chest against the ground. Unlike in the drawing, the tail and the hind legs are visible in The Night Watch.In the recently discovered underpainted sketch which was made visible using MA-XRF (macro X-ray fluorescence) analysis, it can be seen that the dog in The Night Watch was initially depicted with its right front leg more bent, and the chest closer to the ground. In this first rendering, the dogs pose in The Night Watch was even more similar to Van de Vennes drawing.We know that Rembrandt was an avid collector of drawings and prints, and that he did use them as inspiration often, including for several of the militia members in The Night Watch. This was a common practice at the time. There are no records that specifically mention the Van de Venne work in his collection, but another painting by Rembrandt, Joseph Accused by Potiphars Wife (1655), shares not just the theme with Van de Vennes drawing, but Josephs raised hand and eyes turned chastely up towards God and away from Potiphars lustful, adulterous wife.The Rijksmuseum has produced a new six-part video series about The Night Watch which will showcase new details uncovered by the research and restoration teams of Operation Night Watch. The videos will be posted every Wednesday on the museums YouTube channel. The mystery of the dog is the subject of the first video.