or death to him.

Carefully Kennedy took from each tube a few cubic centimeters of the
dialyzate and into each he poured a little liquid from a tiny vial which
I noticed was labelled "Ninhydrin."

"This," he explained as he set down the vial, "is a substance which
gives a colorless solution with water, but when mixed with albumins,
peptones, or amino-acids becomes violet on boiling. Tube number three
must remain colorless. Number two may be violet. Number one may
approximate number two or be more deeply colored. If one and two are
about the same I call my test negative. But if one is more deeply
colored than two, then it is positive. The other tube is the control."

Impatiently we waited as the three tubes simmered over the heat. What
would they show? Seabury's eyes were glued on them, his hand trembling
in the presence of some unknown danger.

Slowly the liquid in the second tube turned to violet. But more rapidly
and more deeply appeared the violet in number one. The test was
positive.

"What is it?" gasped Seabury hoarsely, leaning over close.

"This," exclaimed Kennedy, "is the famous Abderhalden
test--serum-diagnosis--discovered by Professor Emile Abderhalden of
Halle. It rests on the fact that when a foreign substance comes into the
blood, the blood reacts, with the formation of a protective ferment
produced as a result of physiologic and pathologic conditions.

"For instance," he went on, "a certain albumin always produces a certain
ferment. Presence in the blood stream of blood-foreign substances calls
forth a ferment that will digest them and split them into molecules. The
forces of nature form and mobilize directly in the blood serum.

"Let me get this clearly. Albumin cannot pass through the pores of an
animal membrane, since the individual molecules are too large. If,
however, the albumin is broken up by a ferment-action, then the
molecules become small enough to pass through."

Seabury was listening like a man on whom a stunning blow was about to
descend.

"Thus we can tell," proceeded Kennedy, "whether there is such a ferment
in blood serum as would be produced by a certain condition, for when the
ferment is there blood from the individual possessing it will digest a
similar proteid in a dialyzing thimble kept at body temperature.

"Why," cried Kennedy, swept along by the wonder of the thing, "this test
opens up a vista of alluring and extensive possibilities. The human
organism actually diagn