A funny nymph story

I have a vast personal library of fishing/flyfishing books.  More angling books than the Towanda, Sayre, and Bradford County Libraries combined.  Some I've read and put aside.  Some I read at least once or twice a year.  Presently, I'm reading A. J. McClane's book The Masters On The Nymph for my 16th time.
 
I've encountered a humerous story I'd like to share:
 
Dan Todd was an old time fly angler who lived in the Delaware Valley.  He was the stationmaster of the Ulster & Delaware Railroad in Margaretville, NY.  He amassed a considerable collection of trout foods preserved in formalin that he kept in his office.  One morning a man named Olson (whom Dan detested for his murderous consistency in killing large quantities of trout with spoons and worms) saw a mason jar of pebble-type cased caddis sitting on his desk.
 
"What's them things?"  Olsen asked Todd.
 
Dan looked pained.  "I just had an operation.  Them's my kidney stones."
 
Olsen stared closely at the jar.  "God Almighty!  No wonder you can't fish."