>2. Between feeds, some low-fat milk ('foremilk') gradually moves down to
>fill the sinuses.

I thought the foremilk was formed by fluid from the surrounding
breast tissue seeping into the sinuses, thereby diluting the milk
left behind in the sinuses after a feed.  This would explain why the
longer between feeds, the more foremilk there is.  Therefore breast
compression would move milk from the alveoli into the sinuses, which
would increase the fat ratio in the sinuses.

I think this is more or less what Joy said, but I'd like it if
someone could confirm or correct this for me.

Thanks
Jennifer Landels, BA, CE
Vancouver BC