Of course, I would be thoroughly remiss (and I'm sure Dr. Bill would take me to task for it) if I didn't add a few of his more (ahem! ) ribald (albeit always informative) classics:

SUBJECT: Mycobacterium smegmatis

Dear David:
A girl in my class in med school was a good bit older than the rest of us,
because she had had a tyrant mother who would not let her
go until she (the mother) died. She had been a secretary,
and so was very proficient at shorthand, which made her notes
vastly superior to mine. But like many of the other students,
she had the idea that if she let anybody see her notes, it
might help them get above her in class standing. However,
in bacteriology, she kept asking me to tell her what it was
she was seeing in her microscope. So I would look, and then
in her book find the place telling about it.
Then she woulf run up to the prof and tell him what she
had learned, just to make brownie points with him.
He was a friend of my uncle, who just a year
previously had been on the faculty.
But she still
wouldn't let me look at her notes, even though she sat right
in front of me, and there was no chance of their coming to
harm.
When we did cultures of specimens from our own
throats, we first touched cotton swabs to our
tonsils and smeared them on nutrient gelatine media
in Petri dishes, and put them into incubator for a
couple days. When little colonies of germs appeared,
we with platinum loop scooped up a colony,
smeared it on microscope slide, fixed and stained it.
When Annie had made her slide of organisms grown
from her throat culture, as usual she asked me to
come tell her what was on the slide.. Without
any previous plan, something snapped, and I knew how to pay
her back. I looked, and said admiringly;'Why,Annie, you have
the Mycobacterium smegmatis in your throat culture!"
As always, she trotted up to tell the prof about it..
I knew he had noticed what she was doing. He looked like
Groucho Marx, and enjoyed imitating him. So, just as I knew
he would, when she told him she had the Mycobacterium
smegmatis in her throat culture, he tipped his head sidewise,
flutted his bushy black eyebrows, and with a Groucho leer,
asked her if she were inviting comment
concerning her extra-curricular activities. His tone told
her she had been had. She slunk back to her seat, and
looke up the Mycobacterium smegmatis. Suddenly the back of
her neck and ears got very red. That organism is ordinarily
found only on the glans penis and the clitoris.
Annie never bothered me again.
So I was a rat, but I felt it would help her try harder to
help herself. What's your verdict? Bill


[please note: I'm pasting all of Bill's correspondence completely unedited, including any typos]