known tse-tse fly found over a large area of Africa. It has a bite something like a horse-fly and is a perfect blood-sucker. Vast territories of thickly populated, fertile country near the shores of lakes and rivers are now depopulated as a result of the death-dealing bite of these flies, more deadly than the blood-sucking, vampirish ghosts with which, in the middle ages, people supposed night air to be inhabited. For this fly carries with it germs which it leaves in the blood of its victims, which I shall show next."
A new film started.
"Here is a picture of some blood so infected. Notice that worm-like sheath of undulating membrane terminating in a slender whip-like process by which it moves about. That thing wriggling about like a minute electric eel, always in motion, is known as the trypanosome.
"Isn't this a marvellous picture? To see the micro-organism move, evolve and revolve in the midst of normal cells, uncoil and undulate in the fluids which they inhabit, to see them play hide and seek with the blood corpuscles and clumps of fibrin, turn, twist, and rotate as if in a cage, to see these deadly little trypanosomes moving back and forth in every direction displaying their delicate undulating membranes and shoving aside the blood cells that are in their way while by their side the leucocytes, or white corpuscles, lazily extend or retract their pseudopods of protoplasm. To see all this as it is shown before us here is to realise that we are in the presence of an unknown world, a world infinitesimally small, but as real and as complex as that about us. With the cin-
