I recognized Professor Paul Ehrlich from Frankfurt-on-Main, bushy haired, neatly bearded, unaccustomedly smart in wing collar and spotted tie and broadcloth cutaway, with his soft mouth and his glasses halfway down his nose, looking up amiably from some chemical tome as though surprised at someone snatching the habitual box of cigars from under his arm and taking his portrait. In 1909, Ehrlich exploited the German genius for systematic chemistry by testing 605 compounds of arsenic before discovering 'Salvarsan' or '606', which killed the treacherous spirochaete _Treponema pallidum._ He cleared syphilis from the veins of the world, many of them blue-blooded.

On a table against the window a microscope stood tilted for the eye. I idly turned the knurled fine-adjustment screw, focusing the fuzzy blue circle on the glass slide.

I am a biochemist, a student of the molecular mechanism of life, but I had worked on bacteria and recognized a specimen of human pus. I saw the globular scavengers of the blood, resembling the pond amoeba, the simplest of God's creatures, which expresses the mystery of existence in a single cell. Among them were twisted minute, dark, exactly similar dots, some in chains of twenty or more, some in fives and sixes, others in pairs, like broken beads on a ballroom floor. They were _Streptococcus pyogenes,_ an enemy of mankind only less deadly than man himself. Some of the chains had penetrated the blood cells, to lie against the blobs of a nucleus deep stained by the blue dye. The streptococcus germs were winning this complex and subtle battle. They were killing the body's scavengers, on their way to killing the body itself.

I straightened up, noticing with surprise that the colourful, bold landscape which had already caught my eye on the wall above was an original painting. It was an unusual find in the study of a scientific professor.