What is the relationship between disease and art or aesthetics in Thomas Mann's Death in Venice and Tristan? How does this relationship reflect...

Thomas Mann's Death In Venice is, at its heart, entirely concerned with the relationship with disease and art, as symbolised by the setting of Venice itself. As the disease progresses through the story and towards Venice, so does Aschenbach's moral and personal decay and his obsession with the symbol of the aesthetic in the story: the boy, Tadzio. Mann's message is fairly overt. Aschenbach has been in a state of repression for much of his life, incubating, as it were, the "disease" of his naturally artistic nature. Having been restrained for so long, when Aschenbach finally allows his inclinations to break free, they overtake him completely, like a fever pushing him towards insanity. The appearance of Tadzio is only a carrier for Aschenbach's metaphorical disease, rather than the contagion itself. Meanwhile Venice, the city of culture and art, is shown to be sinking deeper daily into its own decay. Venice represents not only the lie that is art—a beautiful front that deceives us into believing there is not something ugly beneath—but also the lie that was Aschenbach's life before he fell into his final two illnesses: the literal sickness that killed him and the passion for aesthetics that drove him mad. 

A similar attitude of distaste towards the so-called "artist" can be seen in the short story "Tristan", in which the artist, Spinell, is described similarly to Aschenbach in his period of decay: as effeminate, affected, and staying in a sanatorium because he "likes the décor". The implication here is evident: an "artist" without morals will wander into the most unhealthy place because of an appreciation for its appearance, without any concern about how it might negatively affect him. Spinell, in the story, is in love with a dying woman who also lives in the sanatorium, the wife of another man. He accuses the other man, Kloterjahn, of having only interest in his wife's body, while Spinell has a deeper appreciation for her soul. This is shown by the narrative to be a falsehood, however, as the two men end up arguing with each other while their supposed beloved, Gabriele, dies in the garden. Thus, a fixation upon art for art's sake in this story is shown to be, as in Death in Venice, a mere cover for moral decay. What is interesting, however, is that "Tristan" also suggests that the opposite extreme--brutish men obsessed with the physical--are also morally corrupt. He seems to indicate that an appreciation for art is important, as is an appreciation for the physically, but that one must include a balance in order to approach to world in a moral way.