The work of the Department of Sanitation is of such primary interest and importance, especially to geographers, that I deal with it separately in the next chapter. CHAPTER V HEALTH ON THE ISTHMUS AND THE FUTURE OF THE WHITE RACE IN THE TROPICS _Yellow Fever._ THE cities of Colon and Panama have never been particularly unhealthy to the Panamanian born, whether white or coloured, or to the West Indian stranger. This population has merely been subject to the malaria common to equatorial towns, especially when in the neighbourhood of swamps, and to the evils which attend imperfect sanitation in a hot climate. The intervening country is very malarious in the low-lying parts, less so on the hilly divide, differing in no way from other similar localities in the same latitude. [Illustration: READING ROOM, EMPLOYEES' CLUB, CULEBRA.] [Illustration: HALL OF EMPLOYEES' CLUB, CULEBRA.] The reputation of the Isthmus of Panama as a death-trap is due to the sickness which (previous to 1906) has always been prevalent among white strangers, and most other visitors, and particularly to the high percentage of death from yellow fever. To this short, sharp, and most deadly disease the native-born is immune; hence the affairs of the city of Panama have gone on well enough for centuries, as far as the residents are concerned, except that travellers by the Isthmian route tarried no longer than they could help. Whenever large numbers of strangers have congregated on the Isthmus, as during the Californian gold-rush, the construction of the railway, and the Canal construction of the French Companies, there has been an epidemic of yellow fever among them, and a very large proportion of cases have terminated fatally. The immunity which the West Indian negro enjoys from this disease gave him a superiority over other labourers on the Isthmus which, since the extinction of the disease, is no longer his. During the American occupation of Havana, after the American-Spanish War, yellow fever broke out among the strangers, and the mere cleaning up of the city, though carried out with military thoroughness, had no effect in checking the disease. A medical board was sent to study the matter. This was in 1900, four years after Major Ronald Ross, of the Indian Medical Service, had discovered the cause of malaria. Ross had proved that the cause of malaria in man was the presence in his blood of an organism introduced by the attack of the _anopheles_ gnat (or mosquito), and that the species was only poisonous to man if it had itself become infected with the germ of this organism in biting a man suffering from malaria. Thus man and _anopheles_ act alternately as hosts to the organism, which apparently requires their co-operation for the continuance of its species.