Kaz had no idea who the Donner Party was, but in this context, it couldn't be anything good. Kaz was used to going to non-medics for medical treatment, too, so his thoughts on Billy's ability to handle this were a lot more callous. Kyle's comment made Kaz curl his lip with disgust. His first impulse was to deny it but then decided it would probably be better if it made him seem more human.

"If you mean other people who have lost a limb just say that."

Definitely more callous. Though the fact he was sticking around might be saying more than he thinks.