Barbara,
I suspect that the infants with Down syndrome that you interpreted as
hypertonic were compensating for hypotonia by "fixing".   I'm sure the
OT's and PT's can explain this one better, but basically the baby
compensates for having a weakness by putting inordinate energy into
holding the body part in question in one position.  I often see babies
who compensate for tongue tie or a low tone tongue by over-using jaw
compression.  This could possibly be the source of the biting you have
observed.
--
Catherine Watson Genna, IBCLC  NYC  mailto:[log in to unmask]