. The Ontario public school hygiene . is not caused by bacteria, which as younow know are plants, but by a very tiny animal, whichpasses part of its life in a mosquito, and the other partin the blood of a human being. Hence, no mosquito,no malaria ; no man, no malaria. It is believed that the germs of 3ellow fever, a veryfatal disease and one much dreaded in the West Indiesand the southern United States, are carried by anotherkind of mosquito—Stegomeyia. At any rate, the recentoutbreaks of this disease have all been successfullyfought by securing great cleanliness and by avoidingmosquito bites
. The Ontario public school hygiene . is not caused by bacteria, which as younow know are plants, but by a very tiny animal, whichpasses part of its life in a mosquito, and the other partin the blood of a human being. Hence, no mosquito,no malaria ; no man, no malaria. It is believed that the germs of 3ellow fever, a veryfatal disease and one much dreaded in the West Indiesand the southern United States, are carried by anotherkind of mosquito—Stegomeyia. At any rate, the recentoutbreaks of this disease have all been successfullyfought by securing great cleanliness and by avoidingmosquito bites. Time from Exposure to Signs of Disease. Malaria 10-30 days Yellow Fever. 2-15 Time from Exposure to Signs of Disease. Scarlet Fever 1-7 days Small-pox 12 There is much more doubt as to the cause of scarletfever and small-pox. Some medical men believe thatthese diseases also are caused by animal germs, but they DISEASE GERMS 43 are certainly not carried by mosquitoes. They seemrather to spread through the air from germs which are. Figure 14.—The statue of Dr. .Tenner. Erected to commemorate his great discoverythat a person becomes immune to small-pox by undergoing vaccination, discharged from the nose, eyes, and mouth, and from bigpimples, or peelings from the skin. 44 PUBLIC SCHOOL HYGIENE CHAPTER X HOW GERMS SPREAD Let us now try to understand how disease germs arespread. But first let me ask you how plant seeds arespread. You have often seen the downy seeds of the dandelionand of the thistle carried along in the wind. Or youmay have noticed burs sticking to the hair of a dog, thewool of a sheep, or the tail and mane of a hard seeds of currants and berries are often seenin the droppings of birds. On one occasion CharlesDarwin got no fewer than 80 seeds to sprout from asmall piece of mud which he had removed from abirds foot. In all these cases, seeds may have beencarried a long distance from the plant or shrub onwhich they grew. The seeds of many common plantsa
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