I made up some data to simulate what you said you have.  There are about
21 Tables missing, but the remainder are left as an exercise for the
reader.  :-)

The example Tables look like these:

[Cell01] Table Datasheet View:

  Hour       mL of O2    mL kg-1
  -----      --------    -------
  436.5      15.1        17
  437        18.2        19

[Cell02] Table Datasheet View:

  Hour       mL of O2    mL kg-1
  -----      --------    -------
  436.5      17.1        17
  437        18.2        19

[Cell24] Table Datasheet View:

  Hour       mL of O2    mL kg-1
  -----      --------    -------
  436.5      22.1        17
  437        19.2        19

I combine them using the following Query (which you'll have to complete
yourself to add the other 21 Tables, but it's an easy pattern):

[Q_TimeVsO2] SQL:
  SELECT T.Hour,  01 AS Cell, T.[mL of O2]
  FROM Cell01 AS T
  UNION SELECT T.Hour,  02 AS Cell,T.[mL of O2]
  FROM Cell02 AS T

  UNION SELECT T.Hour, 24 AS Cell, T.[mL of O2]
  FROM Cell24 AS T
  ORDER BY T.Hour, Cell;

This produces the following combined results:

[Q_TimeVsO2] Query Datasheet View:

  Hour        Cell     mL of O2
  -----       ----     --------
  436.5       1        15.1
  436.5       2        17.1
  436.5       24       22.1
  437         1        18.2
  437         2        18.2
  437         24       19.2

If you need to do any filtering, transformations, &c., I suggest you
leave [Q_TimeVsO2] alone (it's long enough already) and write another
Query based on it that you can use for graphing.

What I did with [Q_TimeVsO2] was to set up a line Chart with 24 data
series (well, actually only 3 ... use your imagination) and based on the
following Query:

[Q_PlotData] SQL:

  TRANSFORM Avg(Q_TimeVsO2.[mL of O2]) AS [AvgOfmL of O2]
  SELECT Q_TimeVsO2.Hour
  FROM Q_TimeVsO2
  GROUP BY Q_TimeVsO2.Hour
  PIVOT Q_TimeVsO2.Cell;

That Avg() function could just as easily have been Max() or Min(), as
there's only one of each value to be plotted.

The values were plotted in multiple series (more imagination needed to
see the graph here), but in tabular form they look like this:

[Q_PlotData] Query Datasheet View:

  Hour          1            2            24
  ------        -----        -----        -----
  436.50        15.10        17.10        22.10
  437.00        18.20        18.20        19.20

  -- Vincent Johns <vjohns@alumni.caltech.edu>
  Please feel free to quote anything I say here.

It sounds as if you are keeping 24 separate tables, one for each cell.  I
would suggest another way of dealing with your data.  Keep all of the data in
one table, but add another column, which will contain the cell number.  When
you create your text files, make sure you include that extra column there, so
as you append new data, it contains the cell number for each record.

When you create your graph, use the cell number field for filtering, and
then choose which cell number to graph out, or select several if you want to
compare them.

Hope this makes sense.  The important thing for a database, is to let the
database do as much of the work as possible.