I began to suspect that he was trying over some phrases for a coming lecture; but it was early yet and I could not decently make an excuse for leaving him. I took a fresh cigar and let him go on without interruption.
“It always seems strange to me how little the man in the street knows of the things around him. The microscopic world has no existence as far as his mind is concerned. A grain of dust is too small for him to notice; it must blow into his eye before he appreciates that it has perceptible size at all. And yet, all about him and within him there lives this wonderful race of beings, passing to and fro in his veins as we do in the streets and avenues of a great city; coming to birth, going about their concerns, falling ill and dying, just as men do in London at this hour. Think of the battles, the victories, and the defeats which take place minute by minute in the tiniest drop of our blood; and the issue of the war may be the life or death of one of us. They talk of the struggle for existence; but the real struggle for existence is going on within us and not in the outer world. Phagocyte against bacterium—that is where the fitness of an organism comes to its ultimate test. A slight hitch in the reinforcements, a minute’s delay in bringing numbers to bear, and the keystone is out of the edifice; nothing is left but a ruin.
“It always reminds me of those frontier skirmishes—a mere handful of troops engaged on either side—upon the issue of which the fate of an empire may depend. Get a new set of enemies, some novel type of bacteria with fresh tactics which the phagocytes cannot cope with—and down comes a human being. It strikes wonder into me, that, you know. A human body is so colossal in comparison with these bacteria that they can have no idea even of our existence; and yet they can destroy the whole machinery upon which our life depends. It’s almost as if a few shots fired in Africa could crumble the whole Earth into an impalpable dust.
“And it is not only within us that these struggles are going on. When you came in, I was just studying some specimens of organisms which are equally vital to us. Come over here to the microscope, Flint, and have a look at them yourself.”
When I had got the focus adjusted to suit my eyes, I must confess that I was astonished by what I saw. Somehow, in the course of my reading, I had picked up the idea that bacteria were rod-like creatures which floated inertly in liquids at the mercy of the currents; but at the first glance I realised how much below the reality my conception had been. In the field of the instrument I saw a score of objects, rod-like in their main structure, it is true, but so mantled with the fringes of their fine, threadlike cilia that their baculite character was almost concealed. Nor were they the inert things which I had supposed them to be; for, as I watched them, now one and again another would dart with prodigious swiftness from point to point in the circle of illumination. I had rarely seen such relative activity in any creature. The speed of their movements was so great that my eye could not follow them in their tracks. They appeared to be at rest one instant and then to vanish, reappearing as suddenly in some fresh spot. I watched them, fascinated, for some minutes, trying to trace the vibrations of the cilia which projected them from place to place at such enormous speeds; but either my eye was untrained or the movements of the threadlike fringes were too rapid to be seen. It was certainly an illuminating glimpse into the life of the underworld.
When I had risen from the microscope table, Wotherspoon took me over to one of the benches before the window and showed me the glass vessels containing the pinkish gelatine. These slabs, he told me, were cultures of bacteria. One placed a few organisms on the gelatine and there they grew and multiplied enormously.
“These specimens here,” said Wotherspoon, “are not the same variety as the ones on the microscope slide. They have nothing whatever to do with disease; and yet, as I told you, they have an influence upon animal life. I suppose you never heard of nitrifying and denitrifying bacteria?”
I admitted that the names were unfamiliar to me.
“Just so. Few people seem to take any interest in these vital problems. Now you do know that internally we swarm with all sorts of germs, noxious in some cases, beneficent in others; but I suppose it never struck you that our bodies form only a trifling part of the material world; and that outside these living islets there is space for all sorts of microscopic flora and fauna to grow and multiply? And need these creatures be absolutely isolated from the interests of animals? Not at all.
“Now what is the essential thing, apart from air and water, which we derive from the outside world? Food, isn’t it? Did it ever occur to you to inquire where your food comes from, ultimately?”
“Well, of course,” I said, “it comes from all over the world. I don’t know whether the wheat I eat in my bread comes from Canada or the States or Argentina, or was
