HEALTH CONDITIONS OF PANAMA. 101 



The average num'ber of workers was : — 



I have taken 1906 as a starting point because that is the first 

 year for which I have been able to obtain detailed statistics. 



I may mention that the last case of yellow fever originating 

 on the Canal Zone was in November, 1905. 



In 191 2 there were living on the Canal Zone, which is in the 

 Tropics, 4,502 white women and children from the United States, 

 and the mortality from disease amongst them was at the rate of 

 5.55 per thousand per annum, a record which compares favour- 

 ably with the mortality rates of women and children in many 

 European health resorts. 



Colonel Gorgas attril^utes the phenomenal success of the 

 Isthmian Canal Sanitation Department to 



The great discoveries in Tropical medicine made during the time 

 between the coming of the French to the Isthmus and the coming of our- 

 selves. 



Colonel Gorgas's policy appears to be based mainly on the 

 following discoveries : — 



1. Tn 1898 Sir Ronald Ross proved that malaria is caused by a parasite 



which is transmitted through the agency of a mosquito belonging 

 to the genus anopheles or other closely related genera. 



2. Tn 1900 and 1901 a Board composed of four surgeons of the United 



States Army Medical Corps conducted a series of experiments in 

 Cuba, which proved conclusively that the virus of yellow fever is 

 conveyed from one person to another by the mosquito stegomyia 

 calopus and in no other way, excepting by experimental injections. 



3. In 1898 Dr. Simmonds claimed to have proved that plague was 



spread by fleas from plague infected rats. This claim was not 

 hnally accepted by medical men until 1905. In 1902 and 1903 Dr. 

 D. J. Verjbitski, by a scries of experiments, showed that plague 

 ; could be communicated to healthy men and animals by bujfs as well 



as by fleas. 



4. In 1900 the United States Government published an abstract of a 



report by the Commission which investigated the origin and 

 spread of typhoid fever in the United States Military Camps 

 during the Spanish War. One of the conclusions of the Commis- 

 sion was that " flies undoubtedly serve as carriers of infection." 

 Previous to the publication of the Commission's Report, Dr. L. O. 

 Howard, Chief Entomologist of the United States Department of 

 Agriculture, had warned the American public tliat the common 

 house fly was in all probability a disseminator of typhoid fever. 



Lieutenant-Colonel Macpherson. of the Royal Army Medi- 

 cal Corps, who visited the Panama in March, 1908, stated in a 

 paper read before the United Services Medical Society, July ist. 

 1908, that there had been a considerable incidence of enteric 

 fever in the labour camps on the Canal Zone, and that 



