"Don't you see? It diagnoses at the very first stage. You take a small quantity of blood, derive the serum, then introduce a piece of tissue such as you wish to find out whether it is diseased or not. The thing is of overwhelming importance. One can discover a condition even before the organ itself shows it outwardly. It means a new epoch in medicine. As for me, I call it the new 'police service' of the organism—working with perfect, scientific accuracy."
"Wh-what do you find?" reiterated Seabury.
"I have made tests for about everything I can suspect," returned Kennedy, taking the tubes and pouring the liquid from number two into number one until they were equalized in color, thus testing them, while we watched every action closely.
"You see," he digressed, "to get the two the same shade I have to dilute the first by the second. Now, the dialyzers are not permeable to albumin. Therefore the violet color indicates that the blood serum in this case contains ferments which the body is making to split up some foreign substance in the blood, such as I suspected and obtained from the hospital. The test is positive. Mr. Seabury, how long have you felt as you say that you do?"
"Several weeks," the man returned weakly.
"That is fortunate," cried Kennedy, "fortunate that it has not been several months."
He paused, then added the startling statement, "Mr. Seabury, I can find no evidence here of poison. As a matter of fact, the wonderful Abderhalden test shows me that you have one of the most common forms of internal disease that occur for the most part in persons at or after middle life, about the age of fifty, more common in men than in women—a disease which taken in time, as it has been revealed by this wonderful test, may be cured and you may be saved—an incipient cancer of the stomach."
Kennedy paused a moment and listened. I fancied I heard someone in the hall. But he went on, "The person whom you suspect of poisoning you—"
There came a suppressed scream from the door, as it was flung open and Agatha Seabury stood there, staring with fixed, set eyes at Kennedy, then at her husband. Mechanically I looked at my watch. It was precisely eight. Kennedy had evidently prolonged the test for a purpose.
"The person whom you suspected," he repeated firmly, "is innocent!"