There are things that we just take at face value in the Sherlockian Canon. We focus and overthink on many a point, but there are a lot of things that few of us stop to think about until something in our lives points us in that direction. So let's talk "Dying Detective."
Victor Savage is murdered by his uncle, Culverton Smith, supposedly with a disease.
The transmission method for this disease? Sharp spring in a joke box pricking the finger.
Like certain folk of the modern day, the writer and people of the story try to tell us this disease is the fault of the Chinese people, which demonstrates how little we've really moved on from the prejudices of the Victorian era. But apart from that business, how was this disease supposedly spread in whatever land it came from? Was there a fad of spring-loaded joke boxes?
This supposed disease seems to need to be introduced right into the bloodstream, but how many blood-borne diseases can live on a steel spring for a day or two?
Remembering tetanus fears of years past, which came up whenever a barefoot kid cut their foot on a rusty nail or piece of glass, one might compare the spring-loaded disease to tetanus, but with tetanus it wasn't the sharp object so much as the bacteria-laden soil around it. Put that rusty nail in a box for a few days, would it still have been as deadly?
Sherlockians have attempted to identify the disease Culverton Smith had weaponized in that manner also used to connect someone like Irene Adler to a more historically based figure like Lily Langtry, but as close as they've come, no direct hits. Smith's disease is like Grimesby Roylott's snake or Professor Presbury's serum of langur, something that seems very much to come from some alternate reality where things work a little differently.
Stepping back from what we are told in the story for a moment, taking the basic facts -- Steel spring pricks finger, victim dies -- the thing starts to sound more like a poison than a disease. And how often in earlier times, did murderers use poisons to kill their victims and blame it on illness? If you listen to murder podcasts at all, you start to notice that happened quite a bit.
Of course, a poison that causes as many disease-like symptoms as we see in "Dying Detective" might be unusual, but we don't really see those symptoms in that story, do we? We see Sherlock Holmes pretending to have symptoms, just to satisfy whatever crazy ideas Culverton Smith (not a real doctor) had in his head to get him to confess.
At a time when we're all refreshing our memories on how diseases are transmitted, the whole steel-spring-in-a-box murder method in "The Adventure of the Dying Detective" starts to look a little more shady than even a shady murder weapon should. But, like Culverton Smith, I'm no doctor. And those guys are a little too busy right now to be thinking about such silliness as joke-box germs of the Victorian era. But it'll be worth another look when time is available, to be sure.