Now it was the opposite. Animal experiments became the main point.

With great caution, so as not to arouse the suspicions of my wife, I resumed my bacteriological experiments alongside my work as a physician, and as ill luck would have it, two of my patients at the time perished within a short period “following successful surgery.” There are such strings of bad luck everywhere, in accordance with the law of large numbers, but here there was a connection, as follows. I was concerned at that time with the etiology of scarlet fever. Notoriously, the bacterial cause of this exanthem (like that of numerous other infectious diseases, I mention only lethargic encephalitis and yellow fever among many) is still wrapped in complete mystery. Every known method has been tried without success despite the greatest experimental ingenuity and the keenest determination. No one on earth has seen the “virus” of scarlatina, scarlet fever, in the flesh! And yet it exists. It must be possible to find it. But how?

Now the matter of scarlet fever is particularly curious. Other pathogenic microorganisms are found as fellow travelers of this disease, identified streptococci readily seen on suitable specimens under the microscope; spherical bacteria arranged in chains can be cultured without difficulty on synthetic growth media. They cause ulcerations, they excrete extremely virulent toxins, they produce, when injected or circulating “naturally” in the bloodstream of the scarlet-fever victim, dangerous effects, beginning with high fever and ending in death.

The following line of thinking seemed plausible to me. The true pathogen of scarlet fever and yellow fever and so forth must, as has been gathered, be so small that it can traverse even the tiniest pores of the clay filter through which the bacillus cultures have been drawn. But the streptococci involved in scarlet fever, while not as big as potatoes, are of measurable size, even measurable volume and weight–and they never pass through such a small-pored filter, they remain in the old culture fluid, while the scarlet-fever toxin and pathogen slip through.

Would it then be conceivable that the unknown scarlet-fever pathogens are tiny freeloaders or parasites living on the much larger bodies of the streptococci, and that they are both being separated by the filter? Some such thing is imaginable, maybe even worth an experiment. Good! I devoted myself to this question, setting up experiments that would answer it one way or the other.

In my office I discharged my tasks as one discharges a duty. I neglected none of the imperatives of antisepsis when I performed the two operations mentioned above. And yet! And yet!

The first was an appendectomy in the “cold” or nonacute stage, generally an entirely safe intervention. Nevertheless a septic fever resembling streptococcal fever had already developed on the evening following the operation. What was inexplicable to my assistant was the appearance of virulent streptococci in the blood of the patient. I will keep it short. We lost the patient. Had I unwittingly transmitted dangerous microorganisms? My wife tried to console me. She took an interest in my successes and failures as a physician. I could not be silent, the thing touched her. I forced myself to stay away from the laboratory for a few weeks. Everything went splendidly in the interval. Even technically difficult operations were successful, and my patients marveled at my “gentle, blessed touch”!

But the day came when it was necessary to transfer the costly and painstakingly prepared scarlet-fever streptococcus cultures to fresh medium. Otherwise these organisms, which were living in the old culture fluid and continuously excreting toxins in the incubator, maintained at a uniform thirty-seven degrees, would eventually have poisoned, sterilized, exterminated themselves. They had to be settled on virgin soil. This job too I performed with extreme care. I used rubber gloves to handle the glass rods tipped with flame-sterilized platinum loops when I transferred tiny drops of the old culture into vessels containing fresh nutrient. My clandestine visit to the laboratory might have taken six or eight minutes at most.