Transmissiuii 19 



who voided the egf^s or in the legs and hands of one of his conu'ades 

 working close by him. . . . These possibilities of infection are 

 repeated every time a man urinates into the water. They are 

 perhaps repeated every day the season of the Nile flood lasts." 



(1909.) Brit. Med. Jonrn.[296] : " When once free from their eggs' 

 shells they [the miracidia] disperse in the water to all sides, and the 

 chance of reaching a suitable shelter considerably decreases for the 

 individual miracidium with time and distance. The more I think 

 of this latter circumstance the more I become convinced that the 

 chief foci of infection — that is, the places where strong and repeated 

 infections are contracted — cannot be found in large bodies of waters, 

 as rivers, canals, ponds, etc., but must be sought in small accumula- 

 tions of water, in which the miracidia, once introduced, cannot 

 become widely dispersed." 



" To render an infection of the skin at all possible . . . the 

 following conditions must be realized : An infected person must 

 urinate (or defalcate) in a place where there is water, however small 

 the quantity. The place must remain moist for some time, but not 

 longer than thirty to forty hours. Within this period another 

 person must bring some part of his skin for some time into actual 

 contact with the moisture. If these conditions are fulfilled the 

 miracidia have the possibility of getting from man to water and 

 from water back to man ; their life-cycle may be closed. 



" The infective power of moist places gradually decreases and is 

 again nil at the end of one or two days even if they remain moist. 

 A recent contamination must take place in order to render them 

 infective again for a short period." 



" The moist places demanded for infection are to be found 

 plentiful about town : in the streets there remain puddles for several 

 days after each rain or for several hours after each watering ; the 

 courtyards of the houses also are often watered especially in the 

 warm season. In many Arabic houses water-closets are an unknown 

 institution or they are of the most primitive type. The calls of 

 Nature are often obeyed in the streets, oftener in the courtyards, 

 especially for urinating. There is thus sufficient occasion for the 

 ground to become over and over again populated with live miracidia : 

 their short life is of no consequence. There only remains the host 

 to supply the miracidia and another to take them up again." 



" Contaminated water loses its infective power again after 

 having been protected from fresh contamination for one or 

 two days." 



(1910.) [297] " Taking the [miracidium] infection by the way of 



