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September, 1909 1881, and in December, 1883, the total number of employes had reached 10,- 000. In October, 1884, the maximum of 19,000 was reached, and an average number of about 15,000 or 16,000 was maintained until 1888, when it fell rapidly, reaching 900 in September, 1889. A total working force of about 700 men was then continued on the Isthmus until 1895, when a feeble at- tempt was made to renew active work on the canal, but the total number of employes never exceeded 4,000. In 1884, of an average total of about 18,000 employes, the deaths numbered 1,232, an annual death-rate of 70.13 per 1,000. From the beginning of the United States occupation it was recognized that the success or failure of the en- terprise would depend not upon the solution of any engineering problems; complex as these appeared, but upon the outcome of the campaign against yellow fever. It had been noted that the introduction of large numbers of non-immunes into a country where yellow fever was endemic was invari- ably followed by an epidemic of the disease, the severity of which varied in direct proportion to the number of non-immunes introduced, and it was well known that an epidemic would soon develop on the Isthmus after the arrival of the American workmen unless aborted by some means. The first step in the campaign against Isthmian diseases was the organiza- tion of a working force that would cover effectively and at once all parts of the field. To this end the depart- ment of health was made to consist of the following divisions: 1. Hospital division, which attended to the sick and injured. 2. Sanitary division, which instituted an active campaign against filth and mosquitoes; and 3. The quarantine division, whose duty it was to prevent the introduc- tion of new sources of infection. Division of Municipal Engineering. Hand in hand with this sanitary or- ganization the engineering department created a division of municipal engi- neering which should at once proceed with the introduction of sewers, wa- ter supplies and paving to make per- manent the results of other sanitary measures. Of the sum total of sanitary Procedures employed, the greater part had to do directly or indirectly with a war against mosquitoes. It had 'been learned by actual experiment in Cuba that yellow fever was transmitted only by a certain variety of mosquito (stegiomya), whose habits of life and "THE MaRINE REVIEW propagation had become well under- stood, and it was the application of this knowledge in the campaign in Panama that produced the results which have amazed the world, and of which we may justly feel proud. Briefly, the handling of the yellow fever question was as follows: Cases were admitted to the hospitals promptly and screened for a few days to prevent the infection of mos- quitoes in the wards that would transmit the disease to other men; the quarters from which cases were taken, and houses recently visited by them, were fumigated by the "fumi- gation 'brigade," to kill all mosquitoes that might have bitten the patient before he was admitted to the hos- pital, and a relentless campaign was carried on against this special mos- quito in its breeding places by the stegiomya brigade, with the purpose of exterminating the species as nearly as possible. Yellow Fever Transmitted by Mos- quitoes. This stegiomya mosquito, the trans- mitter of yellow fever, is rather do= mestic in its habits, preferring to live and breed in and about human dwell- ings; and when you consider that the entire water supply of the community was from open tanks, barrels or tubs kept full by rain in the wet season and scantily' supplied from carts in the dry season, you will appreciate the task of inspecting every water container in the city at least once every six days, and covering and spigotting those that might not be de- stroyed. This inspection of every room in every house was resented by many of the Panamanians as an in- trusion, and they did not hesitate to obstruct the work repeatedly. Then, again, the delays in obtaining supplies as ordered were most disheartening in the early days. Orders of the chief sanitary officer were often cut one-half or even more reduced, and shipments were exasperatingly slow after the goods were bought. The Last Case of Yellow Fever. Through that trying pertod, April to August, 1905, when yellow fever claimed so many victims, when Mr. Wallace's resignation became the signal for an exodus from the Isth- mus that well nigh assumed the pro- portions of a stampede, and when high officials on the Isthmus became so skeptical of the methods of the chief sanitary officer that they were_ ready to ask for his recall his con- fidence in his ultimate success was 333 unshaken, and the patience and cour- age with which he kept his shoulder to the wheel may well be remembered in these later days when there ap- pears to be a disposition in some quarters to question his share of the credit for present conditions. The last case of yellow fever originating on the Isthmus occurred in May, 1906, and there is no danger of a reappearance except as an importa- tion from some of the infected ports within a few days' sail of the canal. It is safe to say that over one-half the physicians on the Isthmus today have never seen a case of yellow fever. The total number of cases since the American occupation was 246, with 83 deaths. Prevalence of Malaria. But, after all, yellow fever was not the disease that most interfered with canal operations, except that its high mortality (one-third of all cases) alarmed employees and_ prospective employees. The disease that causes more loss of time among the work- men than all other diseases com- bined, and consequently the most im- portant economically, is malaria, the severest types of which are found on the Isthmus. Malaria is also trans- mitted from man to man by a certain mosquito (the anopheles), whose habitat is in the vicinity of swamps and pools and slowly moving streams. The anopheles is every- where in Panama, except where her haunts have been destroyed by the anopheles brigade. <A _ peculiarity of this pest is that she does not fly far from her native haunts except in the protection of vegetation or build- ings. The campaign against mataria, then, consists of cutting vegetation about inhabited dwe'lings for a dis- tance of about 1,000 ft. tperfecting suvface drainage to reduce the num- ber of breeding places, and oiling those waters that cannot be drained away, screening houses and adminis- tering prophylactic doses of quinine daily to those who are not sick. The general distribution of the mosquito that transmits malaria and the pres- ense of the malarial parasite in the blood of 70-80 per cent of the native population as determined by actual blood examinations, the only two conditions necessary for perpetuating the disease, is evidence enough that malaria will never be eradicated from the Isthmus, as was the case with yellow fever, but the sum total of anti-malarial procedures has so far reduced the prevalence of the disease that the sick rate among canal em-