Careful attention to background detail is the hallmark of cartoons made in this era. Furniture legs, table lamps, a desk blotter, even the colorful test tubes and so much more. That's because a cartoon like this would be shown at the cinema, along with a newsreel and the feature. Adult audiences would have appreciated the realistic rendition.
Irven Spence returned to MGM when he replaced Michael Lah who was credited for this short.
This is two of the Tom and Jerry cartoons that Don Patterson animated.
Disappearing ink was a popular postwar novelty. It had origins in wartime espionage but later became a mainstream gag trick.