Burton was thinking of the brain even at this early stage of his investigation. In retrospect, it is frustrating that he did not follow this line of inquiry to its logical conclusion. He was prevented from doing this by the evidence of the scans, which told him that clotting began in the lungs and progressed up the carotid arteries to the brain one or two seconds later.

So Burton lost immediate interest in the brain. And his mistake was compounded by his next experiment.

It was a simple test, not part of the regular Wildfire Protocol. Burton knew that death coincided with blood clotting. If clotting could be prevented, could death be avoided?

He took several rats and injected them with heparin, an anticoagulating drug—preventing blood-clot formation. Heparin was a rapid-acting drug widely used in medicine; its actions were thoroughly understood. Burton injected the drug intravenously in varying amounts, ranging from a low-normal dose to a massively excessive dose.

Then he exposed the rats to air containing the lethal organism.

The first rat, with a low dose, died in five seconds. The others followed within a minute. A single rat with a massive dose lived nearly three minutes, but he also succumbed in the end.

Burton was depressed by the results. Although death was delayed, it was not prevented. The method of symptomatic treatment did not work.

He put the dead rats to one side, and then made his crucial mistake.

Burton did not autopsy the anticoagulated rats.

Instead, he turned his attention to the original autopsy specimens, the first black Norway rat and the first rhesus monkey to be exposed to the capsule. He performed a complete autopsy on these animals, but discarded the anticoagulated animals.

It would be forty-eight hours before he realized his error. The autopsies he performed were careful and good; he did them slowly, reminding himself that he must overlook nothing. He removed the internal organs from the rat and monkey and examined each, removing samples for both the light and electron microscopes.

To gross inspection, the animals had died of total, intravascular coagulation. The arteries, the heart, lungs, kidneys, liver and spleen—all the blood-containing organs—were rock-hard, solid. This was what he had expected.

He carried his tissue slices across the room to prepare frozen sections for microscopic examination. As each section was completed by his technician, he slipped it under the microscope, examined it, and photographed it.

The tissues were normal. Except for the clotted blood, there was nothing unusual about them at all. He knew that these same pieces of tissue would now be sent to the microscopy lab, where another technician would prepare stained sections, using hematoxylin-eosin, periodic acid-Schiff, and Zenker-formalin stains. Sections of nerve would be stained with Nissl and Cajal gold preparations. This process would take an additional twelve to fifteen hours. He could hope, of course, that the stained sections would reveal something more, but he had no reason to believe they would.

Similarly, he was unenthusiastic about the prospects for electron microscopy. The electron microscope was a valuable tool, but occasionally it made things more difficult, not easier. The electron microscope could provide great magnification and clear detail—but only if you knew where to look. It was excellent for examining a single cell, or part of a cell. But first you had to know which cell to examine. And there were billions of cells in a human body.