1900.] Bacteria and Savage. 317 



WEEKLY EVENING MEETING, 



Friday, March 9, 1900. 

 Sir William Ckookes, F.R.S., Vice-President, in the Chair. 



Professor Frank Clowes, D.Sc. F.C.S. M.B.I. 



Bacteria and Sewage. 



The discovery made by Schwann, in 1839, that a putrefying liquid 

 swarmed with microscopic living organisms, gave occasion to a long 

 series of remarkable investigations as to the general nature and the 

 life-history of these Organisms, and the chemical changes which they 

 produced. 



Prominent amongst the names of those who prosecuted these in- 

 vestigations stands that of Pasteur, who, in 1857, drew attention to 

 the nature and causes of fermentative changes produced upon sugar 

 solution, of the putrefactive changes in liquids containing animal 

 substances, and of disease changes in the blood of the living animal, 

 which were produced in the presence of various minute living 

 organisms. He showed that, if these liquids were sterilised by heat, 

 and were then duly protected against receiving solid particles from 

 the air, or from other sources, these changes did not occur ; and that 

 contact with air which had passed through a red-hot tube, or had 

 been filtered through a cotton-wool plug, was incompetent to intro- 

 duce the organisms and to start the above changes. 



These researches drew attention to the important part played by 

 the air as a vehicle of the organisms or of their spores, and were 

 supplemented by the researches of Tyndall (1876), who proved that 

 air, which had been allowed to remain at rest until its motes had 

 subsided, was incompetent to produce putrefaction. Tyndall also 

 proved that boiled sterilised broth, when opened in Alpine air, did 

 not- usually putrefy, and that the air near the earth's surface in 

 different localities, and even in the same locality at different times, 

 possessed infective power varying from nil to something considerable. 

 The inference is that the distribution of these organisms and of their 

 spores varies very considerably in any horizontal plane near the 

 earth's surface. 



Percy Frankland (1886) determined the number of these living 

 organisms which could be developed from equal volumes of air col- 

 lected at varying heights from the earth's surface. He made use of 

 hills and cathedral towers for the purpose of collecting his samples, 

 and noted a regular decrease in the number of the organisms which 

 were in the air at greater and greater distances from the earth's surface. 



