In the first half of the two parter "Grave Danger" after Nick is Kidnapped, Catherine and Grissom find entrails at the scene where Nick went missing from. Later when they show Dr. Robbins examining the entrails Catherine walks in and asks the usual questions. But then Dr. Robbins said "I found this and thought that you should see it." Catherine then says "a cecum. dog entrails." and then she walks out of the room treating it no longer as a lead because they were not human. That is untrue. According to the basics of Anatomy humans have a cecum on the starting end of the ascending colon from which the appendix resides. Being people who have expert knowledge in the Human body they should have known this unless this was a blooper they did on purpose to go along with the dog theme for the rest of the episode, but that really was a bad mistake to make.