It is remarkable that anopheles should have bred in this brackish water, as it is a mosquito which generally seeks fresh water. It is probable that the brackish water made some advantageous change in the food supply of the larvæ, and that when the swamp was filled with pure sea water, this food supply was stopped. This is the longest flight of anopheles which we discovered on the Isthmus.
The method worked out by Mr. Le Prince and his assistants was original with them. They would take a screened cage containing a large number of anopheles mosquitoes, and spray them with a solution of analine blue; take them down at night and release them at the suspected spot. They would erect a tent at some convenient place in the town to be examined, put a mosquito-bar in this tent with a man under it as a bait for the lady anopheles, leave the bar open during the night, closing it early in the morning before the anopheles which had bitten during the night had an opportunity to escape. The mosquitoes under the bar were caught and carefully examined. If any blue-stained mosquitoes were found, it was proof that they had come from the point at which the stained mosquitoes had been released the evening before.
The job of acting as bait for the mosquitoes during these investigations was a position much sought after by our negro employees. They were paid by the hour the same wages that the day-laborers received. To be paid full wages for sleeping in a comfortable bed struck the Jamaican as being as near complete bliss as was to be found in this world.
Mr. Le Prince did a great deal of work in experimenting upon the flight of the anopheles at other stations, and during his investigations came across many curious things as to the habits and tastes of the anopheles. He found that the anopheles would show a marked preference for a particular horse; though there might be several other horses near and accessible, they would bite this one horse almost exclusively, the taste of whose blood they seemed to prefer. The same thing was true of men. We had one inspector of whom the mosquitoes were excessively fond. When they were not very numerous, they would scarcely trouble his companions at all, devoting all their attention to him. This poor fellow died as a result of this kind of work. He was Mr. Le Prince’s main dependence for investigations of this kind. He did not suffer particularly from malarial fever while on the Isthmus, but a short time after his return to his northern home, he died of an attack of pernicious malarial fever.
These various methods of combating malaria were very successful. In some of the towns, as I have already said, they were just as successful as they had been in the city of Havana, and I myself have no doubt that, if we could have continued the methods which we inaugurated on the Isthmus, we should have been just as successful with malaria at Panama as we had previously been with the disease at Havana, and at no greater cost. As it was, we succeeded in so protecting the force against malaria that it did not interfere to any appreciable degree with its working capacity.
CHAPTER XV
THE WORK AT THE HOSPITALS
Dr. John W. Ross, of the United States Navy, Major Louis A. La Garde, of the Army, and I had all had a large experience in tropical military service. We were, therefore, thoroughly imbued with the idea that from the very beginning we must make ample and liberal provision for the care of a large number of sick. We were impressed with the fact that the constant sick rate of the Army in the Philippines had been ninety per thousand during the year 1898; that it had been even larger with our Army at Santiago, Cuba. We therefore thought that we should prepare to have at least fifty per thousand of our employees on the Isthmus constantly sick.
Our estimates were based upon fifty thousand employees. If, as occurred with our Army in the Philippines, we should have three hundred per thousand constantly sick, we would need a bed capacity, equipment and personnel for the care of fifteen thousand sick. If, as we hoped, it might not exceed fifty per thousand of our employees sick, we should only need a bed capacity of twenty-five hundred beds. We determined to keep at least fifty beds per thousand for our actual force; that this should be the minimum number, and that the number of beds should be increased as the force increased.
It is a matter of interest to note the fact that during the year that our force was at its maximum, fifty-eight thousand men during the calendar year 1913, we had a hospital capacity of just about twenty-five hundred beds, though the constant sick rate of our employees at this time was only about twenty-two per thousand. The hospital service had become so popular, and had acquired such a reputation for the skillful service and good care which could be obtained there, that a large number of people came to seek its benefits from various Spanish American countries north and south of us.
We had at this time some eight hundred individuals in the hospitals who were not Canal employees. Dr. Ross was determined that our hospital service should be first-class in every respect; that a sick employee of the Canal Commission on the Zone should be able to command just as skillful, and just as good care, as he could command in our largest centers in the United States.