OF WASHINGTON, VOLUME XV, 1913 117 



Both of these species are, in my experience strictly sylvan in habi- 

 tat, never being found beyond the confines of dense bush. Neither 

 I nor any of the party were attacked by Anopheles while traveling 

 up or down the river, during which journeys we camped for a num- 

 ber of nights, entirely without protection, upon the dry shoals at 

 the edge of the river, nor during the whole of my stay near the head- 

 waters. There our protection consisted of a tent fly, open at the 

 sides, pitched at the river's edge and before retiring at night we 

 invariably sat about by the light of lanterns. 



In spite of this exposure and the attraction offered by a consid- 

 erable number of men and unscreened lights, we escaped attack. 

 This may be partly accounted for by the comparative lack of abun- 

 dance of mosquitoes, but their being unaccustomed to feed upon 

 such hosts as man is also suggested as a factor. Some monkeys are 

 present in these forests but large mammals of all kinds seem to be 

 rare and represented principally by a few herds of peccaries, an 

 occasional tapir and very rarely a deer. This may be a coincidence 

 and the correlation, if it exists, between an uninhabited country 

 and biting habits may be purely local, but it must be remembered 

 that the country which Doctor Lutz describes is also normally 

 uninhabited. 



In spite of the conditions I have described, malaria was frequent 

 and severe. 



Malaria is endemic and highly prevalent in Panama and the 

 Canal Zone outside of the controlled areas, and the engineers 

 engaged upon the work had been exposed to infection for more or 

 less lengthy periods during their Isthmian experience. The bush- 

 cutters, boat-men, etc., were recruited principally from among West 

 Indian negroes, long resident in the country and from the native 

 population, more particularly from those of a migratory and roving 

 disposition. From the known prevalence of latent malarial in- 

 fection among the Panamanian population and from the habits 

 of the class of men comprising the laborers attached to the party, 

 as well as the antecedents of the engineers, it is safe to assume that 

 practically every man of the five parties on the work, or possibly 

 150 men, carried with him into the bush a latent infection which 

 required only hardship and exposure to develop an acute attack of 

 malaria. 



