Yellow Fever and Mosquitoes.--Another disease carried by mosquitoes is yellow fever. In the year 1878 there were 125,000 cases and 12,000 deaths in the United States, mostly in Alabama, Louisiana, and Mississippi. During the French occupation of the Panama Canal zone the work was at a standstill part of the time because of the ravages of yellow fever. Before the war with Spain thousands of people were ill in Cuba. But to-day this is changed, and yellow fever is under almost complete control, both here and in the Canal zone, where the mosquito (_stegomyia_) which carries yellow fever exists. [Illustration: Notice the difference in the number of yearly deaths from yellow fever before and _after_ the American occupation of Havana.] This is due to the experiments during the summer of 1900 of a Commission of United States army officers, headed by Dr. Walter Reed. Of these men one, Dr. Jesse Lazear, gave up his life to prove experimentally that yellow fever was caused by mosquitoes. He allowed himself to be bitten by a mosquito that was known to have bitten a yellow fever patient, contracted the disease, and died a martyr to science. Others, soldiers, volunteered to further test by experiment how the disease was spread, so that in the end Dr. Reed was able to prove to the world that if mosquitoes could be prevented from biting people who had yellow fever the disease could not be spread. The accompanying illustration shows the result of this knowledge for the city of Havana. For years Havana was considered one of the pest spots of the West Indies. Visitors shunned this port and commerce was much affected by the constant menace of yellow fever. At the time of the American occupation after the war with Spain, the experiments referred to above were undertaken. The city was cleaned up, proper sanitation introduced, screens placed in most buildings, and the breeding places of the mosquitoes were so nearly destroyed that the city was practically free from mosquitoes. The result, so far as yellow fever was concerned, was startling, as you can see by reference to the chart. Notice also the rise in the death rate when the young Cuban Republic took control. How do you account for that? We all know what American scientific medicine and sanitation is doing in Panama and in the Philippines. [Illustration: Stegomyia, the carrier of yellow fever. (After Howard.)]