102 A MANUAL OF BACTERIOLOGY 



doubt to the conclusion that they do not originate 

 through equivocal generation ; for when nitrogenous 

 material from the animal or vegetal world is heated 

 in flasks, even at as low a temperature as 70 C., all 

 the microbes are killed, and if the entrance of new 

 germs from outside is in every way prevented, and 

 it were possible to keep the flasks for ever, no 

 microbes would ever originate of themselves. On 

 the contrary, the entrance of a single germ, in each 

 flask, is sufficient to cause multiplication, and with 

 it putrefaction. If microbes originate from putrid 

 matter through equivocal generation, putrefaction 

 must appear before the microbes ; but experience 

 shows the contrary, that putrefaction is a conse- 

 quence of the development and growth of microbes. 

 "Within the last few years a theory has been advanced 

 to account for the origin of microbes, which has 

 caused some sensation, viz., that under certain 

 conditions the ordinary mould-fungus will give rise 

 to moving germs of extraordinary minuteness ; such 

 germs are capable of developing into microbes, into 

 yeasts, and finally again into the mould-fungus. 

 When microbes are found in the blood or organs in 

 certain diseases, the authors of this theory of pleo- 

 morphism are satisfied that the spores of the com- 

 mon mould germinate in the human body; that 

 these spores first swarm as microbes, but under 

 suitable culture may be nourished into different 

 species of moulds. However, unprejudiced research 

 has not given the slightest proof that microbes 

 stand in any connection with the dev^pment of 

 yeasts, moulds, or other fungi. They always originate, 



