The exceptionally favorable combination of conditions at New Orleans made possible the testing of the efficiency of fumigation. Vessels, subsequent to fumigation performed either at New Orleans city or at the quarantine station, were thoroughly trapped by the experienced force of trappers operating along the New Orleans water front in connection with plague suppressive measures at that place. Depending on the size of the vessel, from 20 to 140 snap traps were placed on the various ships for periods of 1 to 10 days, according to the ship's stay in port. A record was kept of the number of rats killed by the fumigation and also of those that were subsequently trapped. The excellent records maintained by Passed Asst. Surg. Friench Simpson and his painstaking interest in the investigation made possible a fairly accurate estimate of the efficiency of both sulphur and cyanide fumigations. Such an opportunity of obtaining in a practical way an idea of the results of fumigation for rodent destruction has never before been available, and the data is correspondingly interesting.

There have been ample investigations of fumigations by both sulphur dioxide and cyanide gas under experimental conditions, but such conditions rarely can be said to be identical with the natural environment under which the practice is ordinarily carried out.

Of a total of 182 vessels fumigated by cyanide gas, and irrespective of the part of the ship from which the rodents were obtained, or whether the vessel was empty or loaded, there were recovered 2,811 rats, or an average of 15.44 rats per ship, all killed by the fumigating gas. The trapping on these ships after being fumigated resulted in the capture of 121 rats, an average of 0.66 rat per ship. On this basis of computation, therefore, the efficiency of cyanide gas appears to be 95 per cent, i. e., 95 rats of a possible 100 were destroyed by the fumigation.

Considering a group of 62 vessels treated by sulphur dioxide, the results show 12.05 rats per vessel killed by fumigation, and 3.5 rats subsequently trapped per vessel-an efficiency percentage for sulphur fumigation of only 77 per cent as applied to the entire vessel, irrespective of the holds being loaded or empty. Confining the observations to holds of vessels only, it was noted that the percentage of efficiency of cyanide in empty holds was 99 per cent in a group of 34 vessels recorded, and in a group of 28 vessels the percentage of efficiency for sulphur dioxide was 96 per cent. Thus for empty compartments there was no material variation between the efficiency of sulphur dioxide and cyanide gas as a fumigant, although it will be noted that the exposure to cyanide was 14 hours as compared to 6 hours for sulphur dioxide.

The result of fumigation of loaded holds was unsatisfactory for both fumigants, the percentage of efficiency being 80 per cent for cyanide gas and 64 per cent for sulphur dioxide. The observation of the results obtained in the treatment of superstructures, storerooms, crews' quarters, pantries, poop deck, etc., all compartments that as a rule are filled with dunnage, supplies, etc., indicates the marked superiority of cyanide gas as a fumigant over sulphur dioxide. In a series of 32 vessels treated by cyanide gas the percentage of efficiency of this agent as applied to storerooms and other above-deck compartments, was 94 per cent; whereas that of sulphur

dioxide in a series of 32 vessels was only 55 per cent in the treatment of similar compartments. In other words, whereas sulphur fumigation as applied to superstructures destroyed only 55 rats of each 100, cyanide gas killed 94 per 100.

From reports submitted during the past year it appears evident that fumigation by cyanide gas has many decided advantages over sulphur dioxide for the purpose of destroying rats on ships, the only disadvantage of the former being its greater danger to human life. This feature, however, is not an insurmountable objection and can, with ordinary care and attention by responsible persons, be eliminated. On account of an accident and loss of life incident to the fumigation of a vessel at one of the quarantine stations, due to cyanide gas, the following instructions were issued by the Surgeon General:

SAFEGUARDS TO BE OBSERVED IN PERFORMING FUMIGATION WITH HYDROCYANIC ACID GAS.

TREASURY DEPARTMENT,

BUREAU OF THE UNITED STATES PUBLIC HEALTH SERVICE,
Washington, November 4, 1916.

Bureau circular letter No. 100.

To officers of the United States Public Health Service:

1. When a vessel is fumigated with cyanide gas, no one shall be permitted to enter the various compartments of the ship until entry to such space is declared safe by the medical officer in charge of the fumigation.

2. Subsequent to opening hatches, companionways, and ports, not less than 15 minutes shall elapse before anyone shall enter the superstructures, such as staterooms, cabins, saloon, or forecastle, and not less than one hour before entering the holds. This is the minimum, and the time will be prolonged according to the discretion of the officer in charge.

3. If artificial means for ventilation, such as blower or fan, are not available, wind sails shipped into place should be utilized for aeration of holds.

4. Before declaring it safe to enter holds, a captive animal (guinea pig, rat, cat, etc.) shall be lowered and exposed to the aerial content of such compartments, and the effects produced, if any, shall be a guide in estimating the amount of gas present in dangerous quantity.

5. After measures have been taken to free compartments of cyanide fumes, and the application of test by captive animal indicates sufficient dissipation of the gas to make entering the compartments a safe procedure, they should be entered in all parts by one of the fumigators or by the officer himself. This shall be done as a final step before the officer declares the vessel safe to be entered by the personnel connected with the vessel.

6. Decision as to safety of entering compartments shall be made by the officer in charge of the fumigation and on board the vessel concerned; but during the interval between the sealing of compartments undergoing fumigation and the time appointed for determining the safety of entering, the officer may designate a trustworthy employee or employees to attend to the opening up of compartments, the supervising of installation of blower or wind sail, and the prevention of any persons entering compartments before permission of the officer in charge.

7. The provisions of bureau circular No. 79 of 1915 shall be reviewed and the safeguards mentioned therein shall be observed in addition to the foregoing. 8. You will acknowledge receipt hereof.

1

RUPERT BLUE,
Surgeon General.

Since this circular was issued there have been no accidents attributable to cyanide fumigation, although 900 ships have been so treated in the interval up to the end of the year.

1 Approximately.

The economic saving to shipping when cyanide gas is used is very evident, since the duration of exposure to sulphur dioxide varies from 6 to 12 hours, in contrast to that for cyanide, i. e., 1 hour. While the fumes of sulphur dioxide are not so dangerous to human life as cyanide gas, nevertheless the tendency of sulphur fumes to remain in the holds of vessels for a considerable time not infrequently delays the handling of cargo. Surg. Grubbs reports Surg. Grubbs reports a case where the holds of a vessel retained 2 per cent sulphur dioxide fumes for a protracted period on account of unfavorable weather conditionsthat is, a warm day without wind. Six hours after opening the hatchways the fumes were yet too strong to permit the working of cargo, and it required the use of ventilating fans before the holds were free of gas.

Under natural conditions cyanide fumes generally clear from the holds of average size vessels in 1 hour. Asst. Surg. Faget, in reporting the observations collected during the fumigation of some 33 vessels, noted that 25 of the 33 were free of cyanide fumes within 1 hour after opening the holds, although 4 of the 33 were not clear of the gas at the end of 3 hours. Asst. Surg. Faget attributes the inconstancy of the dissipation of cyanide fumes partly to weather conditions (lack of wind, excessive humidity, low temperature) and ship construction, such as multiplicity of decks and small hatchways. It would appear that of the weather conditions, that of wind is the most important, a fair breeze materially hastening the ventilation of holds and other ship compartments.

Whatever danger attaches to cyanide gas occurs not at the time of the evolution of the gas nor at the opening up of the compartments, but is due to persons entering a fumigated compartment before the dissipation of the gas or dilution to a degree nontoxic to man. Artificial ventilation, therefore, following fumigation both by cyanide gas and by sulphur dioxide seems advisable both for economic reasons (expediting the loading of holds) and for the protection of persons working about the vessel. The device that has proven of greatest practicability of application is that known commercially as the "Aerothrust," a two-blade propeller, 32 inches in diameter, operated by a small gasoline-driven motor. According to Grubbs's observations, an Aerothrust fan of 3-horsepower engine attachment will displace 22,700 cubic feet of air per minute by direct application, or if transmitted through funicular chutes (canvas) 20 feet in length the displacement is reduced to 8,340 cubic feet. The observations at Boston quarantine station indicated that the holds of even the largest vessels, irrespective of weather conditions, when all hatchways are removed, can safely be entered one-half hour after the Aerothrust fan has been in operation. This device is portable, is of comparatively reasonable price, and seems to be best adapted for artificial ventilation of vessels.

VIOLATION OF QUARANTINE LAWS.

For the fiscal year ended June 30, 1917, the department passed on 73 cases involving violation of the act of February 15, 1893, due to failure of masters to present American consular bills of health. Of the total 37 were dismissed without penalty because of extenuating conditions, chief of which was the lack of an American consular representative at the foreign port of departure. In 36 cases mitigated

penalties were imposed, the total amount of fines collected being $1,675.

ASSISTANCE EXTENDED TO OTHER GOVERNMENT SERVICES.

During the year the facilities of the Boston quarantine station were in part extended to the Immigration Service for the purpose of interning some 300 German seamen. Quarters and transportation only were furnished, the Immigration Service attending to the maintenance and general supervision of these interned aliens. The Fishermans Island reservation was temporarily turned over to the Army. The quarantine reservation at Port Royal was also temporarily loaned to the Navy Department for use as a training camp. At Reedy Island quarantine station assistance was extended to the customs, immigration, and naval authorities in boarding vessels at that place, quarters being provided for the representatives of the customs and Immigration Service at the station. The facilities of the San Diego quarantine station were likewise extended to the forces of the United States Naval Reserve, and similar provisions were made at the Tampa Bay quarantine station for assisting the patrol forces in that neighborhood. The above is in accordance with Executive order dated April 3, 1917, as follows:

Under the authority of the act of Congress approved July 1, 1902, and subject to the limitations therein expressed, it is ordered that hereafter in times of threatened or actual war the Public Health Service shall constitute a part of the military forces of the United States, and in times of threatened or actual war, the Secretary of the Treasury may, upon request of the Secretary of War or the Secretary of the Navy, detail officers or employees of said service for duty either with the Army or the Navy. All the stations of the Public Health Service are hereby made available for the reception of sick and wounded officers and men, or for such other purposes as shall promote the public interest in connection with military operations.

THE WHITE HOUSE,

April 3, 1917.

WOODROW WILSON.

Assistance was also extended to the Immigration Service in making sanitary surveys of proposed detention camps for the internment of aliens, and the services of medical officers were furnished for such internment camps.

Table giving transactions at national quarantine stations for the fiscal year ended June 30, 1917.

Alexandria.

Beaufort.

Biscayne Bay

Bocagrande.

Boston..

Brownsville
Brunswick

Cape Charles.

Cape Fear.
Cedar Keys.
Charleston
Columbia River.

Coos Bay...

1 Border station.

Does not include local travelers, who however were subject to cursory inspection.

Table giving transactions at national quarantine stations, etc.-Continued.

During the fiscal year ended June 30, 1917, a total of 12,431 vessels were inspected at the various quarantine stations in the United States. Of this number, 2,796 were fumigated, either for the destruction of mosquitoes as a precaution against the introduction of yellow fever, or for the destruction of rats and other vermin as a precaution against plague.

In addition, 365 vessels were spoken and passed, making a grand total of 12,796 vessels and 709,770 passengers and crews passing under the obervation of the service at ports in continental United States. Following are the summaries of the operations at the various quarantine stations: