INSECTS AND DISEASE. 653 



and inexplicable mystery ; a mystery, however, that may be now pos- 

 sibly explained by man's geographical relations with his zoological tor- 

 mentors, the proboscidean diptera. 



That malarial diseases occur frequently without the development 

 of malarial melanosis is not difficult of explanation. The disease is 

 not permitted to pursue its natural course ; it is interrupted by qui- 

 nine. The individual, moreover, is clothed, or protected from the sun 

 an artificial appendage and addition to the organism which the an- 

 cestrally inherited powers of adaptation could scarcely anticipate would 

 occur. Possibly, if every ague-patient were exposed to a broiling sun, 

 naked, during the chill, and were then suffered to follow the bent of his 

 successive inclinations during the remaining stages of the disease, the 

 accumulated pigment enlarging the spleen would find its natural and 

 more salutary destination in an even distribution over the cutaneous 

 surface a phase in the natural career of the disease which seems to 

 be further indicated by the circumstances that the chills of ague only 

 occur, in typical cases, between sunrise and sunset, the paroxysms get- 

 ting of later and later occurrence, as they are wont to do, until reach- 

 ing sunset, when the night is " skipped," and the attacks begin early 

 next morning. It seems as if Nature required the sun during the chill, 

 in order that her beneficent purpose of protective cutaneous pigmenta- 

 tion should be carried out. 



Although the ethnological bearings of this subject hardly belong 

 to a medical paper, I can not refrain from expressing the suggestion 

 that it is not at all impossible that future study and observation may 

 demonstrate that much of the difference in type between the lowest 

 grade of negro and the most perfect Caucasian white may find its true 

 explanation in the changes produced by an environment of inoculat- 

 ing gnats. Even the characteristic type of the negro skeleton and 

 the capacity of his brain, it is not impossible, may be susceptible of 

 explanation in this manner ; for, when we remember that the spleen 

 and its allies are not the only pigment-forming organs, this function 

 being also performed by the marrow of bones, and when we recall, 

 further, the aching of bones that so often attends an ague-chill, in 

 some cases so severe as to have originated the term "break-bone 

 fever," it is not difficult to conceive that the bone-marrow, like the 

 spleen, may become congested during the chill, and in this way, in the 

 course of time, so far lead to modified nutrition of the osseous struc- 

 tures as to set up, finally, a change of type in the embryological forma- 

 tion of the skeleton. 



In certain tropical regions it has already been observed by ethnolo- 

 gists that tribes inhabiting elevated regions in the interior are supe- 

 rior to those dwelling on low tracts on the sea-coast, the superiority 

 being manifest both in mental and bodily qualities. The lowlands 

 and sea-coasts, however, are favorite habitats of the fever-producing 

 and pigment-producing mosquito. 



