In the early years of our construction malaria was very common and gave a great deal of trouble. As I have explained before, malaria is caused by a small animal parasite which lives in the blood of man and feeds upon the red globules. The excretions of this parasite poison man and cause the fever and other symptoms which we know as malarial fever. This parasite is transferred from the sick man to the well man by the bite of the mosquito. Now it is quite evident that if in any way we can kill the parasites as they exist in man, we not only cure the individual man of malarial fever, but at the same time prevent his being a means of infection for other men who have not yet acquired the disease. In a purely empirical manner, some one hundred and fifty years ago a drug was discovered which man could take without injury to himself, and which, when absorbed into the circulating blood was deadly to the malarial parasite there swimming about. It is somewhat singular that this drug should have been discovered not very far from Panama. A Peruvian Catholic priest found that the Indians in certain parts of Peru cured themselves of the fevers native to that country by the use of the bark of a certain forest tree common to that region. Its benefits were so evident that the wife of the Captain-General of Peru became interested in the matter, and spread about a knowledge of the virtue of this wonderful bark, and introduced it into the mother country and other parts of Europe. This lady was the Marchioness of Cinchona. No drug ever discovered has been as useful to mankind as quinin, and it remains up to the present time one of the few specifics known to the medical profession. Besides curing the malarial patient after he had gotten the parasite into his blood, it was the desire of the Sanitary Department to have the blood of all persons on the Isthmus in such condition that it would not harbor the parasite. We believed that if everybody would take five grains of quinin a day, this quinin would be absorbed into the blood and render the blood so poisonous to the malarial parasite that when the parasite was injected into the blood by the mosquito it could not thrive and develop, but would die. [Illustration: Distilled Water Cart. Culebra.] [Illustration: Ward at Ancon Hospital.]