56 



PHYSIOLOGY OF NUTRITION 



in one of the squares in Paris (Place Saint-Gervais) . The numbers are much 

 larger in cities than in the country. 



Season of Year 



Park of Montsourie 



Bacteria 



Winter. 



Spring . . 

 Summer 

 Autumn 



170 

 295 

 345 

 195 



Moulds 



i45 

 i95 

 246 

 230 



Place Saint- Gervais 

 (Paris) 



Bacteria 



Moulds 



Microorganisms occur not only in the air but also in water and soil. The 

 water of rivers always contains bacteria, these being especially numerous in the 

 vicinity of cities. The following numbers of bacteria were found in a cubic 

 centimeter of water from the rivers and at the localities cited below. 



v r>- / above Lyons 75 



River Rhone Wit o 



I below Lyons 000 



_,. f above Berlin 4,3°° 



River Spree < , , „ .. 



[ below Berlin 97>4oo 



Microorganisms also occur in rain water, in snow and in hail. 



The soil always contains microorganisms, their number naturally depending 

 upon the amount of organic material present. Many more are found near the 

 surface than in the deeper layers. The following table gives an idea of their 

 distribution at various depths in a soil covered with forest growth (at Pfingst- 

 berg, in the vicinity of Potsdam). These are the numbers of microorganisms 

 found in a cubic centimeter of soil from various depths at different times of the 

 year. 



Bacteria are present in all foods, milk furnishing especially favorable condi- 

 tions for their development. When fresh this liquid generally contains no bac- 

 teria, but they develop very quickly from spores that fall from the air. Thus 



