The case of the heartless chicken

News today (reported in the Jerusalem Post, and quickly picked up by the bloggers -- see Jewlicious , who gets straight to the point) is of the Rabbinic counter-attack to the PETA accusations.
I totally agree that to defend the apparent practices at Postville as acceptable shechitah, and the PETA revelations as an attack on shechitah generally, is a **huge** mistake -- not only to the non-Jewish world, but to the Jewish world as well. What kosher-observing consumers want to hear at this point is that Postville was an aberration that will never happen again -- not that the shechitah was kosher, and therefore the animals were by definition dead, and therefore by definition not feeling pain, end of story, everyone who says otherwise is an antisemite and Nazi. (We also want some definitions of what hashgachah actually means , now that the credibility of the long list of 'choshever hashgochos' at Postville has been entirely discredited.)
Anyway .... one of the interesting points raised is how the halacha is going to reconcile current scientific data with psak halachah regarding animals' ability to feel pain after correct shechitah has been carried out. This raises the whole question of halachic adaptation to scientific knowledge, especially where that knowledge contradicts exisitng halachic assumptions.
One of the classic cases here is the 'Case of the heartless chicken', considered by the Chacham Tzvi in the early eighteenth century in Amsterdam. The Chacham Tzvi (Teshuvot 74 et seq) considered the case of a young girl who claimed that she opened a chicken after slaughter, and found that it had no heart. Was it kosher? (Central to the case was the presence of the household cat in the vicinity). The Chacham Tzvi ruled that it was inconceivable, given the state of scientific knowledge at the time, that any animal could exist without a heart, even though classic Jewish sources could be brought to hypothesise such a possibilty. He was attacked for this, but held his ground. In other words -- he based his halachic position fairly and squarely on new, contemporary scientific knowledge.
Poskim dealing with shechitah -- please take note, and stop the King Canute act (who sat on the sea shore trying to command the tide not to come in).

UPDATE: Looking at the refs, or at least the first few listed on Google, it seems that Canute himself initiated this theatre to show his courtiers that he had no power, being fed up with their fawning. That's not quite how I remember it, but you get the principle. You cannot hold out against the tide, or reverse the inexorable facts of nature by commanding them that they are wrong. And, by the way, what have the EDAH or Chovevei crowd commented on the Postville debacle?