526 



Dr. P. F. Frankland. 



[June 10", 



These experiments show that in enclosed spaces, when there is 

 little or no aerial commotion, the number of suspended organisms is 

 very moderate, but as soon as any atmospheric disturbance is occa- 

 sioned either by draughts or by the moving about of people, the 

 number rapidly rises, and may become very large indeed. This is a 

 fact very familiar to all who have had much experience in the 

 cultivation of micro-organisms, and it is of particular importance in 

 connexion with the process of plate cultivation with gelatine. 



The experiments made in the railway carriage afford a very striking 

 example of the enormous number of micro-organisms which become 

 suspended in the air when a large number of persons are crowded 

 together. 



In my own laboratory, where every care is taken to prevent the 

 circulation of dust, the number of organisms did not amount to more 

 than 13 in 10 litres, and of the comparative purity of this air I have 

 had the most abundant evidence in the almost inappreciable amount 

 of aerial contamination which is exhibited by the plate cultivations 

 prepared there. 



In conclusion, I have to express my thanks to the Deans of St. 

 Paul's and Norwich, General Festing, Professor Flower, Dr. Theodore 

 Williams, and Mr. F. B. Colenso, through whose courtesy I have 

 been enabled to carry out many of the experiments recorded in the 

 above paper. 



I must also acknowledge the valuable help which I have received 

 from my assistant, Mr. Hart, A.R.S.M., who is now proceeding with 

 these investigations, the results of which we shall hope to have the 

 honour of communicating later. 



XL " On the Multiplication of Micro-organisms." By Percy F. 

 Frankland, Ph.D., B.Sc, F.C.S., F.I.C., Assoc. Roy. Sch. 

 Mines. Communicated by E> Frankland, F.R.S. Received 

 June 8, 1886. 



In a previous communication " On the Removal of Micro-organisms 

 from Water " (" Proc. Roy. Soc," vol. 38 (1885), p. 379), I had occasion 

 to point out the extraordinary rapidity with which micro-organisms 

 may become multiplied even in ordinary distilled water. It was 

 there shown that if a few drops of diluted urine-water be added to 

 ordinary distilled water and kept in a sterilised bottle plugged with 

 sterilised cotton-wool, the number of micro-organisms remaining sus- 

 pended in the water became multiplied in the following manner : — 



