Day 099 - 08 Mar 95 - Page 21

     
     1        A.  That is right.
     2
     3   Q.   So you put your piece of meat in and you expect then
     4        colonies to form?
     5        A.  Exactly.  You take them away and put them on a suitable
     6        growth medium in ideal conditions and one bacteria will
     7        grow into one colony.
     8
     9   Q.   So if at the end of the growth period you are able to
    10        count, let us say, 500,000 colonies, do you then deduce
    11        backwards, as it were, that you started out with 500,000
    12        bugs?
    13        A.  That is, essentially, it, yes.
    14
    15   MR. JUSTICE BELL:  Presumably, you have a very small number of
    16        colonies and a very small equivalent of the weight of the
    17        original meat, is that how it works?
    18        A.  No, what you have to do, because obviously if you had a
    19        million colonies that would be far too many to count.
    20
    Q.   It would take a long time?
    22        A.  What you would actually do, you take a solution and you
    23        dilute it and you keep diluting it down.  You then factor
    24        that up to -----
    25
    26   Q.   You end up in your solution with the product of an
    27        infinitesimal small amount of meat?
    28        A.  Correct.
    29
    30   Q.   Presumably?
    31        A.  Correct.
    32
    33   Q.   How much of a gramme?
    34        A.  You would normally only ever be able to count up to 50
    35        or 100 colonies on a plate.  So, if you were looking for a
    36        million bacteria, you would dilute your original solution.
    37
    38   Q.   1/10,000th of a gramme of meat, it would be the equivalent
    39        of?
    40        A.  It would be 1/100,000th, yes.
    41
    42   Q.   That was extremely helpful because for myself I had not
    43        understood -----
    44
    45   MR. RAMPTON:  I have been swimming around.
    46
    47   MR. JUSTICE BELL:  I did not know what the mechanism was of
    48        doing it or what the approach was, as it were.  So that is
    49        the whole point of taking a very small amount of meat and
    50        emulsifying it? 
    51        A.  And then you prepare a series of dilutions because, 
    52        obviously, before you do the test you are not sure how many 
    53        organisms are there, so you may be prepare a series
    54        of  ------
    55
    56   Q.   So you divide down and then when you have your reading you
    57        multiply up again?
    58        A.  Exactly.
    59
    60   MR. RAMPTON:  Yes.  We notice there that it says:  "Not more