RIDGEON. Phagocytes.

SIR PATRICK. Aye, phagocytes: yes, yes, yes. Well, I heard this
theory that the phagocytes eat up the disease germs years ago:
long before you came into fashion. Besides, they dont always eat
them.

RIDGEON. They do when you butter them with opsonin.

SIR PATRICK. Gammon.

RIDGEON. No: it's not gammon. What it comes to in practice is
this. The phagocytes wont eat the microbes unless the microbes
are nicely buttered for them. Well, the patient manufactures the
butter for himself all right; but my discovery is that the
manufacture of that butter, which I call opsonin, goes on in the
system by ups and downs--Nature being always rhythmical, you
know--and that what the inoculation does is to stimulate the ups
or downs, as the case may be. If we had inoculated Jane Marsh
when her butter factory was on the up-grade, we should have cured
her arm. But we got in on the downgrade and lost her arm for her.
I call the up-grade the positive phase and the down-grade the
negative phase. Everything depends on your inoculating at the
right moment. Inoculate when the patient is in the negative phase
and you kill: inoculate when the patient is in the positive phase
and you cure.

SIR PATRICK. And pray how are you to know whether the patient is
in the positive or the negative phase?