What clues made homes believe that doctor raylott had a snake?

Homes deduced that Dr. Raylott had a snake based on several clues, including the presence of a mysterious and peculiar odor in the house that suggested the presence of a reptile. Additionally, he found a shed snake skin, which indicated that a snake had been kept there. The doctor's evasive behavior and knowledge about snake venom further supported Holmes's suspicion. Together, these elements pointed toward the likelihood that Dr. Raylott owned a snake.