162 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. I. 



It is evident that an extremely energetic washing was necessary to 

 remove the masses of bacteria in a purely mechanical way (amount of 

 water actually in well calculated at 5 litres, depth of well 8 metres). 



The continued appearance of bacteria after the removal of so much 

 water may be explained by the continual entrance of fresh germs in the 

 incoming ground water at the bottom of the well. But it may also be due 

 to the formation of a zooglea membrane by the bacteria which stick to 

 side of tube and small portions of which being given off to water which 

 passes through would give rise to the constant appearance of germs. It 

 was necessary then to determine the character of the ground water by 

 thoroughly disinfecting the tube. 



On April 27th, water showed the following — 



Litre i 11,200 



" 100 no 



" 500 22 



On the 28th the pump was taken out and placed for two hours in a 

 two per cent, watery carbolic acid solution ; the tube itself was thoroughly 

 washed by means of the long handled brush, and finally live litres of 

 5 per cent solution of Laplace's mixture of raw carbolic acid and sulphuric 

 acid (equal parts of each) was poured into the tube. It quickly sank into 

 the well until finally the water stood at its original height. 



Next day the well was pumped out and the water examined. After 100 

 litres no trace of carbolic acid, either by odor or by ferric chloride reac- 

 tion ; also at 500 litres. Gelatine plates from the water remained sterile. 

 Well remained sterile for seven days after disinfection. There was the 

 possibility that carbolic acid still remained in ground water and so 

 destroyed organisms there present. It was not likely as it must be 

 present in such small quantities as not to affect development. Direct 

 experiment showed that sterile water if artificially infected had no 

 injurious affect on organisms ; this sterility of the water was due to 

 the disappearance of organisms from tube. 



After seven days the well was left for one day without pumping. 

 Next day germs had reappeared. Evidently due to infection from above. 

 Water having been left in undisturbed condition it had had time to 

 develop and form zoogloea stages. 



A second experiment was disinfection with 4 per cent, sulphuric and 

 carbolic acid mixture. Tube was not mechanically cleaned. The results 

 were that same remained germ free for six days. Then there was a 

 gradual reappearance. 



