What role does Meyer Wolfsheim play in The Great Gatsby?

In The Great Gatsby, Meyer Wolfsheim
is Jay Gatsby's mentor, father-figure, accomplice, business partner, a friend, and one
who eulogizes Gatsby after his death.  Really, "Meyer" is an alias that Fitzgerald uses
for Arnold Rothstein, the famous gangster who fixed the 1919 World
Series.

Meyer, in chapter 4, helps to legitimize Gatsby to
Nick during lunch.  He says:

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‘There’s the kind of man you’d like to take home
and introduce to your mother and sister.’.” He paused. “I see you’re looking at my cuff
buttons.”

So, Meyer, like Dan
Cody (in the middle of the book) and Henry Gatz (at the end) is a father-figure to
Gatsby--possibly the most important of all since he helped Gatsby with his "gonnections"
to the underworld.  In other words, he helped Gatsby become great (he helps him amass
his fortune through gambling).

Meyer also serves as an
overt criminal, someone who brags about his human molar
cuff-buttons:

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“Finest specimens of human
molars...”

In The
Great Gatsby, you are what you wear: clothing reveals character and wealth.
 Here, Meyer's cuff-buttons show his power, authority, ruthlessness, and his extravagant
tastes.  In a novel where Daisy cries over Gatsby's silk shirts and Tom shows off his
superiority in his polo outfit, Meyer's cuff-links are a grotesque reminder of his
corruption.  They should signal warning to Nick; however, Nick is strangely attracted to
his power.

In the end, Meyer sends Nick a note about
Gatsby's death.  Tom, Daisy, and Jordan send nothing.  Meyer's notes shows, at the very
least, his compassion:

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DEAR MR. CARRAWAY. This has been one of the most
terrible shocks of my life to me[.]  I hardly can believe it that it is true at all.
 Such a mad act as that man did should make us all think.  I cannot come down now as I
am tied up in some very important business and cannot get mixed up in this thing now.
 If there is anything I can do a little later let me know in a letter by Edgar.  I
hardly know where I am when I hear about a thing like this and am completely knocked
down and out.

Yours truly MEYER
WOLFSHIEM

Remember, it is
Meyer's chauffeur who finds Gatsby's body, and it is Meyer's note here that lays his
mythological story to rest.