CHAPTER IV 



EXAMINATION OF AIR AND WATER IN RELATION TO 

 THE MILK SUPPLY 



Examination of Air — General Note. Air-borne Organisms. Seasonal Varia- 

 tions. Air of byres, dairies, milk-shops, etc. Methods of Examination. 

 Examination of Water : Quantitative and Qualitative. Pathogenic 

 Organisms in Water. 



General note on bacteria in air— 



We have already pointed out in a preceding chapter the 

 important r61e played by air-borne organisms in the contamina- 

 tion of milk. In the byre, in the cooling-room, in transport to 

 point of distribution, and in storage after reaching the hand of the 

 consumer, this contamination continues in more or less degree, and 

 although many of the organisms are harmless from a pathogenic 

 point of view, yet others undoubtedly may at times play an 

 important part in the spread of disease. 



It must be borne in mind that fresh country air away from 

 centres of population may be regarded in still weather as practically 

 free from bacteria, although, according to the season of the year, it 

 will contain a more or less considerable number of the hyphomycetes 

 or mould fungi. At high altitudes, the air may be looked upon as 

 practically germ free, although here again the lighter spores of the 

 mould fungi may cause them to be carried by air currents to a very 

 great height. The experiments of Pasteur are well known. In the 

 recent researches of Dr Jean Binot of the Pasteur Institute,^ lOO 

 litres of air taken at the summit of Mont Blanc did not contain 

 a single microbe, and the total number of organisms varied 

 between 4 and 11 per metre cube (1000 litres). An examination 

 of the air of the interior of M. Janssen's Observatory, situated on 

 the highest point of Mont Blanc, and taken in two different rooms, 

 gave, on the other hand, 540 and 260 organisms per metre cube. 



^ Communication d PAcademie des Sciences de Paris, 17 Mars 1902. 



