"I tried mopping the floors with rather a strong solution of creolin but it did little good. Previous experience with pyrethrum was not very satisfactory. Knowing the volatility of naphthalene in warm weather and the irritating character of its vapor led me to try it. I took one room at a time, scattered on the floor five pounds of flake naphthalene and closed it for twenty-four hours. On entering such a room the naphthalene vapor will instantly bring tears to the eyes and cause coughing and irritation of the air passages. I mention this to show how it acts on the fleas. It proved to be a perfect and effectual remedy and very inexpensive, as the naphthalene could be swept up and transferred to other rooms. So far as I am concerned the flea question is solved and if I have further trouble I know the remedy. I intend to keep the dog and the cats." CHAPTER X OTHER DISEASES, MOSTLY TROPICAL, KNOWN OR THOUGHT TO BE TRANSMITTED BY INSECTS SLEEPING SICKNESS One of the worst scourges of Africa and one that is to-day attracting world-wide attention is the disease known as trypanosomiasis, the terminal phase of which is sleeping sickness, one of the most ghastly diseases that we know. 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. The group is being studied extensively and every day our knowledge of them is increasing so that we now know quite definitely the life-history of several. _Trypanosoma lewisi_, a parasite of rats, is perhaps the best known as it is always common where-ever rats are found. Sometimes as many as 30% or 40% of the rats of certain districts are infected. It is thought that these are transmitted from rat to rat by the common rat-louse which serves as an intermediate host. Fleas may also act as disseminating agents. A few other kinds cause serious disease of animals, but we are more interested just now in the particular one that is causing so much trouble in Africa. This parasite was discovered in 1902 and was named _Trypanosoma gambiensi_ (Fig. 111). Since then it has been found to be widely distributed. Although the natives have doubtless long been subject to the disease caused by this parasite, the recent influx of whites to these regions and the consequent movements of the natives have caused a great spread of the disease so that whole regions are now made desolate, the inhabitants dying or fleeing to escape the uncanny death.