Responsa of the Rashba, Part I
Teshuvot haRashba part I 98:1
The Rashba engages with the question of whether treifot are fixed by tradition or subject to empirical verification, weighing in on the tension between Talmudic authority and anatomical/medical knowledge — a key parallel discussion to the Ramban's position.
...Regarding the question of an animal which suffers a wound which would be considered a treifa, and behold, it lives more than 12 months, should we say that since it lived more than a year, the wound was not in fact a treifa - and thus the animal should be considered kosher? My answer is, if you have seen or heard of someone who is lenient in such a case, do not listen to them! Anyone who is would claim that this animal is kosher is, in my eyes, as one who is insulting the words of the Sages.... everyone who is truly God-fearing must be as a firm wall against this, and not to make the words of the Sages like a broken and pierced wall, through which the fox enters...