460 CHAMBERLAIN. 



very doubtful in our minds whether chemical rays of the sunlight and 

 complexion types of Caucasians are factors of any importance in tropical 

 pathology. The experiences of Gorgas in Panama, the reports of various 

 other workers from many countries, and our own general observations 

 in the Philippines, all lead us to the conclusion that the main cause of 

 tropical deterioration, as seen in the past, was infection of the skin, 

 blood, intestines, and other regions, with those parasites which are more 

 common in tiie Tropics than in the temperate zone. The vast improve- 

 ment in the health conditions in Cuba, Panama, and the Philippines, 

 which has followed action based on such a parasitic theory, is strong 

 evidence in favor of our assumption. The enervating effects of con- 

 tinued heat and humidity doubtless play some part, especially in the 

 direction of discouraging out-door exercise. Nostalgia, isolation, and 

 monotony, and the excessive use of alcohol resulting therefrom, are 

 factors of considerable importance. To account for what is observed 

 in the Philippines it does not seem to us necessary to call in the 

 hypothetical action of the actinic rays in the sunlight, nor do we think 

 that there is any adequate evidence that such action is a factor in 

 tropical morbidity and deterioration. It appears that the men who 

 spend much time actively engaged out of doors in the Philippines 

 are the ones who remain in the best health. Those who suffer most 

 from nervous affections are the women, and they pass practically all 

 their time in. the shade. The situation is well described by Castellani 

 and Chalmers who state that "the basis of the largest proportion of 

 illness and death in the Tropics is bad sanitation and not climatic 

 influences." <7) 



The direful effects of the Philippine climate, which have been so vividly 

 depicted by Woodruff, relate to the earlier days of the American occiipa- 

 tion and are not seen at the present time. It is our belief that these 

 unfortunate occurrences were due chiefly to infections resulting from the 

 poor hygienic conditions unavoidable in the early campaigns. It does 

 not seem that any effort is now made to spare officers or men from ex- 

 posure to the sunlight, yet the morbidity and the mortality continually 

 decrease. Affections of the nervous system, including insanity, are among 

 the diseases considered by Woodniff to be particularly likely to occur in 

 the Tropics, as a result of excessive light stimulation, and he bases his 

 argument on statistics from the reports of the Surgeon- General covering 

 the calendar years 1901 and 1902. To determine if the same argument 

 holds good at the present time, the figures for the last seven years for 

 which statistics are available have been compiled from the reports of the 

 Surgeon- General of the Army and are shown in Table XXIX. 



