It is impossible to advance in ADA without turning back again and again, now because of the return of two words: Pastrouil and varicolored, plus a bespattered milk-maid.
While reading about Van´s adventures in Villa Veen and still thinking about Fartingben or Fartukoff´s warning about a dangerous contamination ( a venereal disease, I assumed ), I came across the word "milkman", soon after a description of a catamite´s distressing dysentery, "defaced by varicolored imprints of bestial claws...".

"Their joint efforts failed, however, to arouse the pretty catamite, who had been exhausted by too many recent engagements. His girlish crupper proved sadly defaced by the varicolored imprints of bestial clawings and flesh-twistings; but worst of all, the little fellow could not disguise a state of acute indigestion, marked by unappetizing dysenteric symptoms that coated his lover’s shaft with mustard and blood, the result, no doubt, of eating too many green apples. Eventually, he had to be destroyed or given away (...) In 1905 a glancing blow was dealt Villa Venus from another quarter. The personage we have called Ritcov or Vrotic had been induced by the ailings of age to withdraw his patronage. However, one night he suddenly arrived, looking again as ruddy as the proverbial fiddle; but after the entire staff of his favorite floramor near Bath had worked in vain on him till an ironic Hesperus rose in a milkman’s humdrum sky, the wretched sovereign of one-half of the globe called for the Shell Pink Book..."

"Milkman": a "cowboy", perhaps. But then I remembered the "accidental milkmaid" who was as bespattered by blood as both seconds, "Mr. de Pastrouil and Colonel St Alin".

"had bespattered two hairy torsoes, the whitewashed terrace, the flight of steps leading backward to the walled garden in an amusing Douglas d’Artagnan arrangement, the apron of a quite accidental milkmaid, and the shirtsleeves of both seconds, charming Monsieur de Pastrouil and Colonel St Alin, a scoundrel, the latter gentlemen separated the panting combatants, and Skonky died, not ‘of his wounds’ (as it was viciously rumored) but of a gangrenous afterthought on the part of the least of them, possibly self-inflicted, a sting in the groin, which caused circulatory trouble..."

In B.Boyd´s Ada Online I found: charming Monsieur de Pastrouil: Signficance unknown.
Colonel St. Alin, a scoundrel: a play on the name of Soviet dictator Joseph Stalin (1879-1953), whose name does not usually suggest saintliness. Whether or not Stalin exists on Antiterra is a moot point: see 582.19-20.

Milkmaids brought to my mind two names: Louis Pasteur (1822-1895), the first scientist to admit that small-pox was caused by microorganisms and the British doctor Edward Jenner ( 1796) who discovered a "vaccination" ( a new word that refers to "cow" - in French, "vache", in Portuguese, " vaca" ) by observing a milkmaid´s immunity to small-pox after contagion with "cow-pox".
Pastrouil could be the scientist Louis Pasteur? And small-pox, or "varíola", could it be also have been indicated by a word such as "varicolored" ( multicolored), plus all the symptoms of fever, pain and intestinal problems that come before the rash and the pustules?

But then, why not Pastrouil and Nerjen, for example, as the seconds, instead of St. Alin? Is there another kind of contamination ( such as the spread of "varicolored lands") that arises not by an organic, tesselated or biological kind, but in reference to Antiterra´s political affairs? What was Fartukoff´s real warning?