CONTENTS ix 



SECTION III 

 PHISIOLOGY OF MICROORGANISM 



CHAPTER PAGE 



IX. Effect of Physical Environment upon Microorgan- 

 isms 115 



Rates of growth and death — Effect of Ught — Effect of 

 heat — The minimum temperature — Optimum growth 

 temperature — The maximum temperature — Growth 

 temperature range — Thermal death point — Effect of 

 .electricity — Effect of X-rays and radium rays — Effect of 

 pressure — ^Effect of osmotic pressure — Effect of desicca- 

 tion. 



X. Physical Effects Produced by Microorganisms 127 



Light produced by microorganisms — Production of heat — 

 Changes in viscosity — Effect on osmotic pressure. 



XI. Effect of Chemical Environment upon Microorgan- 

 isms 131 



Effect of chemicals on direction of movement — Effect of 

 chemicals on direction of growth — Effect of chemicals 

 on rapidity of growth — Effect of hydrogen ion concen- 

 tration on rapidity of growth — ^Effect of oxygen upon 

 rapidity of growth — Effect of kinds of nutrients present 

 — -Effect of concentration of nutrients — Stimulating 

 effects of dUute poisons — ^Effect of autogenic substan- 

 ces — Effect of chemicals upon rate of death — Charac- 

 teristics of an ideal disinfectant — ^Effect of hydrogen 

 ion concentration upon death rates — ^Alkalinity or alka- 

 lies — Salts of the heavy metals— The non-electrolytes — 

 Oxidizing agents — Essential oils — Stimulation of disin- 

 fection — ^Autogenic products — Use in therapeutics. 



XII. Chemical Changes Produced by Microorganisms 



Energy Relationships 147 



Sources of Energy — Sunlight as a source of energy to mi- 

 croorganisms — Oxidation as a source of energy for micro- 

 organisms — Methods of securing energy by oxidation — 

 Cycles of the elements — The nitrogen cycle — The car- 

 bon cycle — The sulphur cycle, 



XIII. Mechanism of Chemical Changes Produced by Micro- 



6rganisms — -Enzymes and Fermentation 157 



Enzymes — The hydrolj^ic enzymes or hydrolases — The 

 splitting and oxidizing enzymes — Fermentation — The 

 origin of the products of fermentation. 



