“This is particularly useful as the production of the intoxicating liquor sold at the trial is much more satisfactory as evidence than is oral evidence of an agent that he bought and consumed liquor at a certain time, open as it is to all the attacks against oral testimony and to the further attack that an agent who consumes a considerable quantity of liquor in the course of a day is liable to impeachment as a witness on the ground that he was likely intoxicated and therefore his testimony is not to be believed.”
