I'm fairly sure that Lovecraft was having his little joke when he describes Dr. Muñoz as "obviously of superior blood," given what we later find out about the good doctor's blood. This brings up the possibility that he contrasts Dr. Muñoz intentionally with, and thus purposely denigrates, the other lodgers, "mostly Spaniard a little above the coarsest and crudest grade." The same can be said of the contrast between Muñoz' cultured Lovecraftian tones with the stereotyped diction of the landlady, Mrs. Herrero. I'm not sure if it makes it better, or worse, that HPL is consciously using racial or ethnic stereotypes to improve his fiction.
Note that we have entered the realm of the dead -- not just the cold, but the "room smelled like a vault of a sepulchred Pharaoh in the Valley of Kings." Note that workmen and laborers (what HPL would no doubt consider "the lower orders") instinctively fear the doctor, just as animals do a vampire or werewolf. In the absence of animal life, Lovecraft (and other writers of urban fantasy or horror) need some sort of spoor denoting a disturbance of the natural order.
Because Muñoz is not merely a scientist, but a magus. Just as alchemists used highly technical equipment in magical pursuits, so the doctor uses not just "an absorption system of ammonia cooling" and "a scientific enhancement of will and consciousness" (mesmerism? psychic powers?) but "exotic spices and Egyptian incense," and "the incantations of the mediaevalists." We have another note about how Lovecraftian magic functions: "he believed these cryptic formulae to contain rare psychological stimuli which might conceivably have singular effects on the substance of a nervous system from which organic pulsations had fled." We're more than halfway to the Essential Saltes already.
And just what awesome story hooks lie under this section?
"He acquired a habit of writing long documents of some sort, which he carefully sealed and filled with injunctions that I transmit them after his death to certain persons whom he named -- for the most part lettered East Indians, but including a once celebrated French physician now generally thought dead, and about whom the most inconceivable things had been whispered."****
And this is just an average Lovecraft story.
NEXT: "The Call of Cthulhu"