Report on the Bacteriology of Water. 



245 



Part II. 



" Experimental Investigations on the Behaviour of Bacillus 

 anthracis in Water." By Professor Marshall Ward, D.Sc, 

 F.R.S., assisted by G. E. Cartwright Wood, M.D., B.Sc * 



It is obvious that some of the questions raised in our Report can 

 only be settled by experimenting directly with the freshly collected 

 water, and, since we selected a definite type of Thames water for our 

 work, ib was necessary to determine the main points in the natural 

 history of this water itself, and to employ it directly for cultures. 



Some of the principal results are submitted as follows : — 



Bacteriological Examination of the Thames Water in its Natural 



Condition. 



Preliminary. 



On January 21, 1892, three samples of Thames water were sub- 

 mitted to examination immediately after collection, to obtain an 

 answer to the question, Does the Thames water selected for inquiry 

 contain bacteria at the moment of collection ? 



Plate cultures were made in the usual way, by dropping known 

 quantities, so many drops from a pipette containing 1 c.c, and 

 known to emit so many drops per 1 c.c, of the water into gelatine 

 melted at 30° C. 



Sample I gave the following results : — 



(a.) 1-drop plates incubated 5 days at 15° C. (drop = c.c.) gave 

 an average of 2 colonies per plate = 46 bacteria per 1 c.c. 



(b.) 3-drop plates in 7 days gave an average of 8 colonies per 

 plate = 61 bacteria per 1 c.c. 



(c.) 9-drop plates in 5 days gave an average of 8 colonies per 

 plate = 10 bacteria per 1 c.c. 



So far, it was clear that the river water contains some bacteria, 

 30 to 61 per c.c, which develop on gelatine. These were of several 

 kinds, and developed at different rates, and pure cultures of the 

 different forms were isolated for future reference, as it was part of 

 our object to familiarise ourselves with the normal bacterial flora of 

 the river. 



Samples II and III were similarly examined, and with similar 

 results, which need not be detailed here. 



* All experiments on animals hare been made by Dr. Cartwright Wood. 

 VOL. LIU. S 



