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TILE AMERICAN MUSEUM JOURNAL 



gence that leads us, or ought to lead us, 

 to the use of microscopes, laboratories, 

 and through these to a successful com- 

 bat with disease; but as an oflfset to 

 this, she has, as a rule, made us more 

 susceptible to disease tliaii are the lower 

 animals. As far as we know the ante- 

 lope with trv])anosom('S in the l)lood is 

 not made ill Ijy them. Tlie killing of 

 the vast herds of buffalo that once 

 ranged our own western prairies was 

 necessary in order that these lands 

 might support great herds of cattle : 

 and so perhaps when the Dark Conti- 

 nent comes to be settled, it mav be 

 necessary to kill most or all of the wild 

 game animals in oi'dci- to cliiiiinatc this 

 terril)le disease. 



One of the most jiecnliar of all tropi- 

 cal diseases, and one that is very com- 

 mon in some parts of Africa, is filari- 

 asis, caused by a ]iarasite called the 

 filaria. In the blood of persons sulTer- 

 ing from it there are found innumer- 

 able little worn)s that can be seen only 

 by the aid of a microscope. These are 

 present only at night in the hhiod that 

 is circulating. At about iive o'clock in 

 the afternoon they begin to ajJiH'ar in 

 the blood, having been hidden away in 

 the body until this time, aiul thev rt'- 

 main in the eirculatiiui until about 

 midnight when they begin to diminish. 

 By eight or nine o'clock in the morning 

 they have all disa])])eare(l, and a search 

 of the blood under the microsco]je after 

 this fails to reveal any. They are ]iow 

 collected in certain large blood vessels 

 deep in the body, especially in the 

 lungs, where they remain hidden until 

 they go out on their next nocturnal ex- 

 cursion. 



The parasite is conveyed to human 

 beings by the bite of certain kinds of 

 mosquitoes. The mosquito bites, and 

 takes from a man (or from some ani- 

 mal as the case may be) blood which 

 contains these small worms. In the 

 stomach of the mosquito (the interme- 

 diate host) the parasite goes through 

 certain definite changes or metamor- 

 phoses which are Just as necessary to its 

 complete life as are the different phases 

 in the lives of butterflies, moths, and a 

 great many insects. First it escapes 

 from a skin or shell in which it has 



existed. Then it Ijores its way through 

 the wall of the mosquito's stomach, and 

 travels forward through the body until 

 it arrivt's at the base of the bill or pro- 

 boscis. Here it curls itself up and waits 

 until its host begins to feed upon a 

 warm-hlooded animal, when it passes 

 out and finds its way into the circu- 

 lation of the animal. These filariae 

 behave in a curious way which has the 

 same effect as though dictated by intel- 

 ligence: that is, when the mosquito, in 

 the al)sence of animal food, feeds Upon 

 fi'uit. such as bananas, the filaria does 

 not leave its comfortable berth but con- 

 tinues to wait until it has the chance to 

 entei' the circulation of a warm-blooded 

 animal. A ])ossible explanation of this, 

 however, is that when a moscpiito bites 

 a human being, it first injects a small 

 iimount of fluid secreted in its salivary 

 gland. 'I'his fluid prevents the blood 

 fi'om coagidating and stopping up the 

 \crv small bill through which it is 

 drawn. 'I'his poisonous substance is 

 the cause of the swelling and itching 

 that follow mosquito bites. It is not 

 known but that the filaria is injected 

 along with this, for it is fair to assume 

 that the insect would not nee(l to inject 

 the seci-etion when feeding on Ijananas, 

 as banana juice does not coagulate. 



When tlie parasites find themselves 

 injected into the blood of a man. the 

 "final host," they travel about in the 

 circulation until they find a resting 

 ])lace in one of the larger main lymph 

 vessels, and here they settle down for 

 the rest of their lives, one or more males 

 and one or more females coiled up to- 

 gether. From this point they send out 

 into the ])lood current every evening 

 innumerable broods of young which are 

 the ones that rest by day and circulate 

 by night ; and so the life cycle is run, 

 over and over again. Their nocturnal 

 activity is supposed to be related to the 

 fact that their intermediate hosts, the 

 mosquitoes, carry on their predatory 

 excursions after dark, and therefore it 

 would be of no avail for the little para- 

 sites to get into the circulation in the 

 daytime. This is an evidence of Na- 

 ture's thought for the preservation of 

 a species that, from our point of view, 

 is useless. 



