REDEEMING THE TROPICS 



347 



His efforts were rewarded with suc- 

 cess. He proved beyond every perad- 

 venture that the Anopheles mosquito is 

 the intermediate host, and that no one 

 can contract malaria except he be bitten 

 by a mosquito which has previously bit- 

 ten a person suffering from that disease. 



In telling of his achievement, Ross de- 

 clared: "The exact route of infection of 

 this great disease, which annually slays 

 its millions of human beings and keeps 

 whole continents in darkness, was re- 

 vealed. The minute spores enter the sal- 

 ivary gland of the mosquitoes and pass 

 with its poisonous saliva directly into the 

 blood of man. Never in our dreams had 

 we imagined so wonderful a tale as this." 



But even Ross little dreamed when he 

 made his great discovery that the won- 

 derful tale his astute mind had unfolded 

 was to be but the beginning of a long 

 series of related discoveries which would 

 end entirely humanity's helplessness in 

 the face of epidemic diseases. 



The medical world had hardly ceased 

 to wonder at the work of Ross when 

 Reed, Carroll, and Lazear, of the U. S. 

 Army Medical Corps, proved — Lazear at 

 the cost of his life and Carroll at the cost 

 of a severe spell of yellow fever — that 

 the Stegomyia mosquito plays the same 

 role with yellow jack that the Anopheles 

 does with malaria. 



HOW MOSQUITOS, RATS, AND FXlES SPREAD 

 DISEASE 



Then came others with their discover- 

 ies that bubonic plague is transmitted by 

 fleas carried on rats and ground-squir- 

 rels ; that sleeping sickness is carried and 

 transmitted only by the tsetse-fly ; that 

 dengue is carried by other species of 

 mosquitoes, and more recently that the 

 body louse is the culprit which carries 

 typhus from man to man. 



Likewise has our increasing knowledge 

 of the principles of the spread of typhoid 

 fever led us to the point where the only 

 reason we contract it is because some one 

 has been careless with the excreta that 

 comes from persons having typhoid in 

 their systems. We know that milk is a 

 frequent vehicle of infection. We know, 

 through the researches of Dr. Howard 

 and his associates, that the house-fly, 



which he has christened the "typhoid fly," 

 constantly furnishes free transportation 

 for germs that are seeking an entrance to 

 some human system. We know how 

 much water has to do with its dissemina- 

 tion, from the fact that in cities in Eu- 

 rope where there is a perfect water sup- 

 ply the number of cases is seldom above 

 ten per hundred thousand people, and in 

 America seldom above twenty per hun- 

 dred thousand, while in cities where there 

 is impure tap water the rate goes up to 

 two hundred and even three hundred per 

 hundred thousand population. It has 

 come now to be accepted by sanitarians 

 that in any average city of considerable 

 population and ordinary sanitary regula- 

 tions all sickness from typhoid fever over 

 twenty cases per hundred thousand in- 

 habitants is attributable to the water. 



How much the fly has to do with the 

 spread of the disease is illustrated by the 

 experience of the army encampment at 

 Jacksonville during the Spanish-Amer- 

 ican War. The lime that was carried on 

 the feet of the flies from the latrines to 

 the mess-tables showed that nearly all of 

 the hundreds of cases of typhoid that in- 

 fested the camp were caused by germs 

 carried to the food of the men from the 

 latrines. The fly has been caught red 

 handed in divers instances. Some of 

 them have been permitted to walk over 

 infected material and then to walk over 

 culture plates. In every case almost 

 every point on which they set their feet 

 brought forth a colony of typhoid germs. 

 In other cases flies have been caught and 

 given a bath in sterile water, with the 

 result that a single bath has brought a 

 hundred thousand germs from the body 

 and legs of one fly. 



THE SAD HISTORY OF "TYPHOID MARY" 



There is one class of people who are a 

 permanent menace to humanity. About 

 2^ per cent of those who contract ty- 

 phoid fever live to become germ carriers. 

 The germs like them so well that they 

 agree to dwell in peace and harmony 

 with their hosts ; but as they go about 

 they spread a trail of typhoid fever. An 

 illustration of this is to be had in the 

 case of that celebrated woman, "Typhoid 

 Mary." She had suffered an attack of 



