@jAujAl1

Explanation for each joke : * The telegraph was the ancestor of the phone line, except it didn't transmit sounds, but beeps depending on button presses on either end, and you could transmit individual letters using a combination of short and long presses following the Morse code alphabet. The telegraph was using a long network of electric lines across the country, but at the beginning of the century, some recent technological breakthroughs, mostly from the Italian inventor Guglielmo Marconi, allowed wireless telegraphy to work using radio waves, even opening up the first transatlantic communication lines. You could say the wireless telegraph was practically sending "words over nothing". * The original oyster soup jokes goes something like "Waiter, I can’t seem to find any oysters in this oyster soup." and the waiter to reply "Why, would you expect to find angels in angel cake?" (alternative reply: "Would you expect to find soldiers in a soldier biscuit") which implies the restaurant cheapened out on expensive oysters and used a clever comeback to justify it. Finding an oyster in a tomato soup, however, would at the very least be quite surprising. * Painter's colic was a symptom of lead poisoning which came from paints using lead in their recipes at the time. Back in the 16th century, some makeup even used lead carbonate powder for its pale yellowish color, most famously in Venetian ceruse. Catching painter colic from a kiss on a cheek would indicate the recipient of the kiss was wearing an abundant quantity of such lead-based makeup. * The trace is the part of the harness that attaches the horse to a wagon, so in this context "leaving without a trace" is a pun that could either mean that the thief left no hint, or that he was very thorough in his robbery and left nothing. * The doctor being a woman implies the "incurable heart disease" is an anti-euphemism for "falling in love". Edit: added some context on lead powder makeup thanks to @dzinypinydoroviny's remark.