Anne,
The 7 minute myth came from a study published in Lancet in the 1970's I
beleive (volume 1 or 2, I think) by Dr. Lucas of the breastmilk and IQ in
preterm infants studies.  His work is at least partially funded by artificial
baby milk manufacturers (Farley's), and the milk he uses in his studies to
compare to special preterm formulas is drip milk collected in a
breast shell while the donor nurses her own full term baby.  He used donor
milk in an
attempt to randomize out the mother and just get the effect of the breastmilk.
 I would have loved to see the point difference in the IQ study if he had used
the infants' own mother's preterm milk pumped with a quality electric pump!  I
do not know why he chose to use drip milk as opposed to pumped milk.  You
cannot get a lower quality/calorie/fat milk than drip milk.  Other concerns
with drip milk are contamination from contact with the skin and prolonged
warmth from body heat.  Dr. Lucas said at the 1994 ILCA conference that the
next study he would like to do is to take the mothers of premies who have
decided not to bf or porvide their milk, and randomize them into a bottle
feeding and breastfeeding group.  He feels  half the babies who would
otherwise not get human milk from their mother would get it, and he could
totally eliminate the maternal factors associated with the decision to
breastfeed (higher Socioeconomic status and education, etc.)  He also said
that his own research has convinced him of the value of human milk over the
years, that he was not previously a proponent of breastfeeding. The 7 minute
study came from that earlier period in Lucas' career.
        Sorry so wordy, but I wanted to give you some background.
        I believe Michael Woolridge did studies of the increasing fat content
of human milk obtained over time during a feeding.  Paradoxically, Woolridge
often publishes in Lancet as well. This is the one I use to justify longer
breastfeedings for slow gaining babies.
        Todays electronic scales would make a test of the 7 minute myth
possible by interrupting and test weighing breastfeeding babies at intervals
throughout a feeding.  Any takers?
Catherine Watson Genna, IBCLC