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Hit them and they fall off, only to rise again and attack once more; for their bodies are so tough and resistant, that great force is required to destroy them. They are infected with trypanosomes, a kind of attenuated worm that circulates in the blood, but fortunately not the variety that causes sleeping sickness. At least we believe not.
Large doses of arsenic may keep a fly-struck horse alive for months; alive, but robbed of all his life and fire, his free gait replaced by a shambling walk. The wild game, more especially the water buck and the buffalo whose blood is teeming with these trypanosomes, but who, from generations of infection, have acquired an immunity from these parasites, keep these flies infected.
Among the Protozoa referred to in one of the earlier chapters mention was made of certain trypanosomes which inhabit the blood of man and certain animals. Very little was known concerning these parasites previous to the beginning of the present century, but since that time several have been found to be of great economic importance.
This man had used an arsenic compound called atoxyl, till his blood was filled with it and its effects on the trypanosomes nil. There was but one wild experiment more to try the stolen blood of another." Craig paused to let the horror of the crime sink into our minds.
Laveran proved the association of haematozoa with malaria in 1880. In the same year, Griffith Evans discovered trypanosomes in a disease of horses and cattle in India, and the same type of parasite was found in the sleeping sickness.
Some are already beyond saving. It would be interesting to know whether there are trypanosomes or other blood-parasites in whales. I suppose that no one has an ill-feeling towards whales. Most of us have never seen a whale, either alive or in the flesh only a skeleton.
These animal microbes are often spoken of as "blood-flagellates" or hæmo-flagellata, and the larger kinds are called "Trypanosomes," or "screw-form parasites," or whilst a series of more minute ones are called "Piroplasma," or "pear-shaped parasites." Many, but not all, are found during a certain period of their life, actually inside the corpuscles of the blood.
The trypanosomes are fighting with the normal blood cells. Here we have the lowest group of animal life, the protozoa, at work killing the highest, man." Kennedy needed nothing more than the breathless stillness to convince him of the effectiveness of his method of presenting his case. "Now," he resumed, "let us leave this blood-sucking, vampirish tse-tse fly for the moment.
It would now be a matter of extreme interest to ascertain whether the few dwindled herds of bison in North America are infected by trypanosomes, and no doubt we shall soon receive reports on the subject. A most interesting branch of this subject of the unthinking extermination of great animals by man is that of the extermination of whales. Man is worrying them out of existence.
Some of the Lithuanian bison have lately been dying in an unaccountable way, and on investigating a dead individual a Russian observer has discovered a "trypanosome" parasite in the blood. The trypanosomes are microscopic corkscrew-like creatures, of which many kinds have become known within the last ten or fifteen years.
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