BACTERIAL FLORA OF RIVER-WATER 271 



doubted, for Ward established the remarkable fact that the 

 walls of the hyphae contain no cellulose, but are composed of 

 chitin. Onygena has, in fact, abandoned a plant for an animal 

 nutrition. This would place the germination of the species at 

 a great disadvantage. But he found that this difficulty was 

 overcome by the spores which had been licked from the skin 

 germinating in the gastric juice of the animal's stomach, and, 

 when voided in the excreta, infecting a new host by accidental 

 contact. In the case of both Stereum and Onygena he accom- 

 plished for the first time the difficult task of tracing their life- 

 history from spore to fructification. 



Ward had prepared himself for the study of bacteria, and 

 in the nineties he undertook, with Prof. Percy Frankland, a 

 prolonged research on behalf of the Royal Society as to the 

 conditions of their occurrence in potable water. The reports of 

 the results fill a thick volume, and the amount of work involved 

 is almost incredible. The bacteriology was entirely due to 

 Ward. 



That bacteria are not an inevitable element in potable water 

 is proved by their absence from that of deep springs. They are 

 arrested by filtration through the earth's crust. In any river 

 system they are comparatively fewer towards the watershed, and 

 more frequent towards the mouth. The obvious conclusion is 

 that they are derived from the drainage of the land. As it is 

 known that the bacteria of cholera and typhoid are water-borne, 

 it becomes a problem of vital importance to ascertain if river 

 water is a possible means of distributing these diseases. Ward 

 set to work to ascertain : (i) What was the actual bacterial flora of 

 Thames water; (ii) if this included any pathogenic organisms; 

 (iii) if not, what became of them.-' The labour required by the 

 first two branches of the enquiry was enormous; he identified 

 and cultivated some eighty species; the resulting answer to the 

 second was happily in the negative. 



As to the third, two facts were known. First, that river 

 water, if stored, largely cleared itself of bacteria by mere sub- 

 sidence; secondly, that Downes and Blunt, in a classical paper 

 communicated to the Royal Society in 1877, had shown that 

 exposure to direct sunlight is fatal to bacteria in a fluid medium. 



