Q:

what word class is the 'follow' in 'as follows'?

I am curious about this sentence, 

The list is as follows.

Can I take it as original form for ?

a) The list is as it follows.
b) The list is as (many) follows.

That is, I'd like to know if 'follow' is a verb or  a noun.

A:

The expression "AS FOLLOWS" is now idiomatic and is an elliptical version of,
AS IT FOLLOWS, 
which in Fowler's view  is now a cataphoric phrase. Fowler writes, "The reason for its fixed form is that it was originally an impersonal construction= 'as it follows ' ".
OED defines the phrase as a prefatory formula used to introduce a statement, description,  list or the like. It cites earliest example from year 1426.
als here fast folowys.(as here directly follows)
So 'follows' is a verb always singular, no matter the subject  of reference is singular or plural or what it goes on to elaborate is a long list.
Garner's Modern American Usage-3rd.ed.-also  endorses the view that expression is shortened from  of 'as it follows'.  He says, "even for enumeration of many things the expression is elliptical for 'as it follows' – not as they follow." He goes on to refer Lindley Murray, An English Grammar 222(5th.ed.1828) to show 'follows' we make use of in the phrase is an impersonal verb as in 'as it appears' and, therefore, should be "confined to singular number, the construction being ' as it follows ', 'as it appears ' ".
Back to basics, ' follow'  remains a verb of one dummy "IT". We may consider the rest as hereinabove to be just meaningful digression.

