Jacob receiving Joseph's tunic - Velázquez

Joseph's brothers, having sold him to Midianite merchants, stain his tunic with goat's blood and make old Jacob believe that his youngest son has been devoured by a wild beast.
The scene before us is one of mystification, constructed by Joseph's brothers to deceive Jacob. It refers to a factitious scene of Joseph's death, a virtual, invisible scene. The blood-stained tunic is the central instrument of this mystification. Velázquez shifts it slightly to the left, so as to create an empty space between Jacob and his sons, a central void around which they all seem to be meditating (see in particular the attitude of Jacob's closest brother, in his red tunic, one hand against his chin). This void is nevertheless occupied by the father's cane, fallen to the ground, which indicates what is at stake in the mystification: who will raise this cane, who will recover the father's sceptre?
The dog, in the foreground on the right, is a symbol of the mystification. The dog, in the right foreground, seems to be barking at the mystifying brothers: is it Joseph's dog, indignant at what has been plotted against his master? At the same time, it serves as a visual clutch for the scene, like the dog in Veronese's Banquet at Levi's .