Final answer:
Mark Twain did not directly protest against animal cruelty and research in a specific written work according to the information provided. His stance on animal welfare can be inferred from the broader historical context of the middle-class reformers' responses to animal acts in his era. Twain's literary works often addressed societal issues, but there is no direct evidence of a written protest against animal cruelty in the references provided.
Step-by-step explanation:
The inquiry about Mark Twain's protest against animal cruelty and research does not appear to correspond directly to a specific written work. Although Twain, born Samuel Langhorne Clemens, was a noted humorist and author who often used literature to criticize societal norms and injustice, such as slavery and social hierarchy, the provided references do not highlight a specific instance where he protested animal cruelty and research in a published work. However, Twain's general stance on animal welfare can be inferred from broader historical contexts, such as the middle-class reformers' reactions against animal acts at Coney Island, which were contemporary to Twain's lifetime.
Despite being best known for his novels like Adventures of Huckleberry Finn and his story The Celebrated Jumping Frog of Calaveras County, Twain's views on animal cruelty might be part of his less-known personal beliefs or activities not covered in major literary works or easily accessible historical records. It's conceivable that Twain, as a prominent public figure of that era, may have had opinions on such matters, as did other social reformers of his time.