Why, I could tell well in advance when any particular fly was making up its mind to begin to play.  There are a thousand details in this one matter alone that I shall not bore you with, although these details did serve to keep me from being bored too utterly during that first period in solitary.  But one thing I must tell you.  To me it is most memorable—­the time when the one with a grouch, who never played, alighted in a moment of absent-mindedness within the taboo precinct and was immediately captured in my hand.  Do you know, he sulked for an hour afterward.

And the hours were very long in solitary; nor could I sleep them all away; nor could I while them away with house-flies, no matter how intelligent.  For house-flies are house-flies, and I was a man, with a man’s brain; and my brain was trained and active, stuffed with culture and science, and always geared to a high tension of eagerness to do.  And there was nothing to do, and my thoughts ran abominably on in vain speculations.  There was my pentose and methyl-pentose determination in grapes and wines to which I had devoted my last summer vacation at the Asti Vineyards.  I had all but completed the series of experiments.  Was anybody else going on with it, I wondered; and if so, with what success?

You see, the world was dead to me.  No news of it filtered in.  The history of science was making fast, and I was interested in a thousand subjects.  Why, there was my theory of the hydrolysis of casein by trypsin, which Professor Walters had been carrying out in his laboratory.  Also, Professor Schleimer had similarly been collaborating with me in the detection of phytosterol in mixtures of animal and vegetable fats.  The work surely was going on, but with what results?  The very thought of all this activity just beyond the prison walls and in which I could take no part, of which I was never even to hear, was maddening.  And in the meantime I lay there on my cell floor and played games with house-flies.

And yet all was not silence in solitary.  Early in my confinement I used to hear, at irregular intervals, faint, low tappings.  From farther away I also heard fainter and lower tappings.  Continually these tappings were interrupted by the snarling of the guard.  On occasion, when the tapping went on too persistently, extra guards were summoned, and I knew by the sounds that men were being strait-jacketed.

The matter was easy of explanation.  I had known, as every prisoner in San Quentin knew, that the two men in solitary were Ed Morrell and Jake Oppenheimer.  And I knew that these were the two men who tapped knuckle-talk to each other and were punished for so doing.

That the code they used was simple I had not the slightest doubt, yet I devoted many hours to a vain effort to work it out.  Heaven knows—­it had to be simple, yet I could not make head nor tail of it.  And simple it proved to be, when I learned it; and simplest of all proved the trick they employed which had so baffled me.  Not only each day did they change the point in the alphabet where the code initialled, but they changed it every conversation, and, often, in the midst of a conversation.