4 A MANUAL OF BACTERIOLOGY 



satisfactorily without the presence of bacteria. Levin 

 also found that the intestinal tract in many Arctic 

 animals the polar bear, reindeer, seal, eider duck, etc. 

 is generally sterile, so that these animals are able to thrive 

 without the intervention of intestinal bacteria. 



Commercially, micro-organisms are of the utmost 

 importance. Without them there would be no fermen- 

 tation, arid the wine, beer, and indigo industries, the 

 ripening of cheese and tobacco, and many like processes 

 would be non-existent. From a financial aspect also 

 micro-organisms cannot be ignored ; thus, many of the 

 so-called " diseases " of beer and wine, which often occa- 

 sion serious loss, are due to the entrance of adventitious 

 forms, and the existence of the silk and wool industries 

 in France was once threatened owing to the ravages of 

 pebrine among the silk-worms and of anthrax among the 

 sheep, but through the genius of Pasteur these troubles 

 were overcome. There is no need to emphasise the im- 

 portance of micro-organisms from a medical and hygienic 

 point of view, but the fact may be recalled that sixty 

 years ago the mortality after operations was very high, 

 and that 40 per cent, of these deaths were caused by 

 pysemia, septicaemia, and hospital gangrene, conditions 

 which are due to the entrance of micro-organisms, and 

 which are now almost preventable by means of the 

 antiseptic system of treatment introduced by Lord Lister 

 and its further development, the aseptic system. 



The theory of spontaneous generation or abiogenesis is 

 intimately associated with the study of bacteria. The 

 putrefaction of animal and vegetable fluids even after 

 boiling, and the growth in them of minute living forms, 

 were held by many to be a sure proof of the development 

 of life from inanimate matter, of the spontaneous genera- 

 tion of the living from the non-living. A succession of 

 investigators, however, showed that (1) if the fluids be 



