investigators that these creatures are the sole agents of inoculation into man of the germs of malaria, yellow fever, sleeping sickness, plague, East-coast fever, Kala-azar, typhus fever, recurrent fever and other maladies which have brought suffering and death to millions of people. In most cases they are not merely mechanical bearers of disease germs from one victim to another, for if that were so the problem of discovering the part they play would be relatively simple. Usually their bodies are breeding-places of microscopic organisms which they suck from the blood of one victim-beast or man-and these parasites, after undergoing profound transformations within their hosts, are afterwards injected into other victims. Insects have thus been shown to be intimately related to the life of man; and a branch of study which was formerly considered to be of purely zoological interest has proved to be closely connected with practical problems of European colonisation in tropical regions. If it is better to save life than to destroy it, then laud and honour should be given to those patient scientific investigators whose studies have shown how to lessen human suffering and prevent the spread of fatal diseases. Before a disease can be prevented it must be understood; there must be a knowledge of its nature and mode of transmission if a sure remedy is to be found, and that knowledge is obtained by the man of science, whose work meets with little encouragement either officially or publicly, and is usually without reward. No better examples could be found of the benefits of such work to the human race than are afforded by the studies of tropical and other diseases carried on in recent years. Perhaps the most important of these diseases is malarial fever, which causes the death of more than a million people yearly in India alone. When Sir Ronald Ross was carrying out at Bangalore the intricate and minute researches required to determine the cause of malaria and its remedy, he wrote the pleading lines: In this, O Nature, yield, I pray, to me. I pace and расе, and think and think, and take The fever'd hands, and note down all I see, That some dim distant light may haply break. The painful faces ask, can we not cure? We answer, No, not yet; we seek the laws. The unseen, small, but million-murdering cause. At that time it was believed by most people that malaria was caused by some kind of vapour or "miasma which rose from swampy or marshy land. It is now known to be transmitted by a certain kind of mosquito which can harbour the germs of the disease and convey them from one person to another. This conclusion seems simple enough, but it was only proved to be true by slow steps and persistent work. The theory that mosquitoes are carriers of disease, and that malaria is transmitted by them or flies, was put forward fourteen centuries ago, and was revived in more modern times, but systematic practical study was necessary to establish it. The links of evidence by which the mosquito has been convicted of causing many millions of deaths from malaria were not forged together until recent years. First, Dr. C. L. A. Laveran, a French army surgeon, studying malaria in a military hospital in Algiers, discovered that the blood of a person suffering from malaria always contains a peculiar parasite or organism. Sir Patrick Manson then suggested that these parasites pass a part of their existence in the bodies of mosquitoes, which carry them from one person to another. When in the blood of a human being the parasites are in a certain stage of development, but they can only complete their life-cycle in the body of their insect host. To Sir Ronald Ross belongs the honour of tracing the various stages of the existence of the parasite in the body of the mosquito until it was ripe for injection into a human being by the bite of the insect. He proved by numerous experiments that the only means by which a healthy person can acquire malaria is by the bite of a mosquito which has previously bitten someone whose blood contains the particular organisms associated with the disease. In other words, if there were no mosquitoes of the kind required by the malarial parasites to complete their life-cycle, there could be no malarial fever. On the eve of this remarkable discovery, Ross offered up a prayer of thanks which makes a beautiful supplement to the lines written several years before: This day relenting God Hath placed within my hand Seeking His secret deeds, With tears and toiling breath, I find thy cunning seeds, O million-murdering Death. I know this little thing A myriad men will save. The cause of the disease having been found, the remedy was evidently to stamp out the mosquito, so far as possible, by searching out its breeding-places and |