I have not touched upon the numerous internal parasites that prey upon humanity. Only a scientific expert ought to risk telling extensively of these incredibilities. Among them is the _eye-worm_, one of the _Filaria_, which in spite of its euphonious name is an abomination. It is a white, thread-like worm, an inch long, that goes all through the body beneath the epidermis. It becomes visible only in the white of the eye, and while there a doctor can remove it. But it must be done, not only with extreme care, but promptly, for it does not stay long in one place. It is extremely irritating in the eye, but in other parts of the body, although it causes distressful itching, it is not so irritating as one would expect. It sometimes causes swelling, especially in the back of the hand. Every few days my forearm or my hand was swollen from the presence of this worm. I have seen a ridge across the nose where a colony was passing. I have been told that the eye-worm and the worm that circulates beneath the epidermis are not identical. I am not sure about it; but I hope there are not two of them. The guinea worm belongs to the same family, with the beautiful name, the _Filaria_. The larva enters the human body in drinking-water and makes its way to the subcutaneous tissue of its host’s leg, where it often causes serious abscesses. It grows rapidly, curling round and round and raising the skin. It often reaches a length of ten feet and sometimes more. All African houses are infested with rats and mice. The white man has introduced the cat. But there are still very few and they are so highly valued that among the Fang in late years a cat has been made a part of the dowry which a man pays for his wife. It was several months after our first house was built at Efulen before we were able to procure a cat from the coast. In that time the rats had full possession of the house and merely tolerated us. They gambolled all night over the beds in which we were sleeping, and over ourselves, sometimes even getting under the cover. I had always abhorred them, and I was led to use a mosquito-net, not for mosquitoes, but to keep the rats out. I never got so used to them but that I sprang out of bed whenever they got into it. Finding that the mosquito-net did not altogether suffice, I hit upon the happy expedient of keeping a lamp lighted in my room all night. This was effective to some extent, but only by driving them into the rooms occupied by my fellow missionaries, Dr. Good and Mr. Kerr, whose abhorrence of them, however, was not equal to mine. They wondered why I kept the lamp burning, but I did not tell them; for if we all had lamps the rats would have no choice of room, and surely a man has some right to profit by his own discovery. I desisted from this practice as soon as Dr. Good solved my purpose, which he did one night after he had gone to bed, and instantly announced it with a shout.