118 

 6 



the fever-producing substances which 

 produce the symptoms ot malaria. 

 I have given but a rough outline of 

 the process, but it will serve to show the 

 main points of this complicated life- 

 history. 



It will be seen, however, that the 

 process of infection by Anopheles is 

 7iot a simple mechanical transference of 

 blood from infected to healthy people, 

 that human cases can only infect the 

 Anopheles at a particular stage in the 

 history of the parasite in their blood, and, 

 particularly, that an Anopheles which 

 does not bear in its poison gland the 

 thread-like spores of malaria representing 

 the last stage of the extra corporeal cycle 

 of the organism passed wiihin its body 

 is as harmless as an empty gun. 



It will be readily understood that the 

 work of Ross and his colleagues in other 

 parts of the world gave a huge impetus to 

 the study of insect-borne diseases, and it 

 has borne noble fruit. The connection 

 of Yellow fever with Havana is almost 

 proverbial, and the average deaths from that 

 disease alone were over 800 in each year. 

 It has been estimated that some 36,000 

 persons died of it from 1853 to 1900, and 

 in addition the island of Cuba and ad- 

 joining parts of Brazil acted as an 

 endemic focus, whence, at various times, 

 the disease spread to many parts of the 

 world, mcluding Spain, Africa, and even 

 England. In 1897, there were 6000 

 deaths from it in Cuba. In Bio from 

 1868-1897, 41,726 deaths. The Southern 

 States of America have also experienced 

 dreadful visitations from it. " Yellow 

 Jack " was a dreaded name throughout 

 South America, the West Indies, and the 

 Southern United States. With the open- 

 ing of the Panama Canal and the conse- 

 quent shortening of the voyage from 

 these localities to Australia and the Far 

 East, it is very probable that Yellow fever 

 will some day be introduced to this side of 

 the world. Three or four years ago, Aus- 

 tralian sanitarians regarded this possi- 

 bility with awe and foreboding ; to-day 

 they look upon it certainly as a serious 

 problem, but as one which would give 

 comparatively little trouble compared to 

 the introduction of a few cases of small- 

 pox. I will endeavor to explain how this 

 remarkable change in views has come 

 about. 



In 1900, after the occupation of Cuba 



by the American forces, a commission 

 of four medical men was appointed 

 to investigate the alarming prevalence of 

 Yellow fever there, and to devise, if pos- 

 sible, means for combating ifc» A great 

 deal of work had been done by various 

 observers in seeking for the cause of it ; 

 but nothing was accurately known, and 

 the early work of the commission, devoted 

 to the examination of the blood and 

 tissues of patients, only served to disprove 

 previous theories, and not to discover 

 anything new. Absolutely nothing 

 was apparent in the blood or 

 elsewhere as a result of the 

 most careful bacteriological research. 

 The next step was to enquire into its pro- 

 pagation. Now, one attack of | Yellow 

 fever safeguards the patient against a 

 second one, producing a condition of im- 

 munity, as it is called. It had been noted 

 that patients could be safely nursed by 

 non-immune nurses, and that patieats 

 discharged after an attack did not cause 

 fresh outbreaks of disease in those non- 

 immune persons they came in contact 

 with. It was obviously, therefore, not 

 contagious, nor did the infection persist 

 in a virulent form in the discharges. The 

 next matter was to settle the disputed 

 question of the mfectivity of clothing and 

 bedding which had been in contact with 

 patients. To this end, a small hut was 

 erected, very deficient in ventilation, and 

 specially constructed so as to maintain a 

 hot moist atmosphere within it. The 

 windows and doors — please note this — 

 were carefully screened with fine wire 

 gauze, of small enough gauge to prevent 

 the entry of mosquitoes. Into this house 

 were piled sheets, blankets, mattresses, 

 pillows, and clothing of all description 

 from the Yellow fever hospitals, and 

 amongt them, in the beds and covered 

 with the bedding of patients, who had 

 just died of Yellow fever, even wearing 

 the clothing taken from the bodies, and 

 stained with the blood and " black vomit" 

 discharge, seven young non-immune 

 Americans, including members of the 

 commission, slept two or three at a time 

 for a total period of sixty-three nights in 

 all. Not a single one of these non-im- 

 mune men developed the disease. This 

 effectually proved that clothing and bed- 

 ding alone were incapable of conveying 

 the disease, however grossly they were 

 contaminated. 



