CHAPTER IV. 



NON-PATHOGENIC MICRO-ORGANISMSFUNGI. 



IT is quite outside the scope of the present volume to 

 describe any bacteria other than those giving rise to 

 disease processes. In the course of his work the bacteriolo- 

 gist frequently comes across ordinary saprophytic organisms. 

 These may occur in diseased organs in which putrefaction 

 has already begun to take place, and they may therefore 

 appear in cultures made from such organs. Their source 

 in cultures may, further, be by contamination from the air, 

 or from the use of insufficiently sterilised vessels or instru- 

 ments. The positive characters of the pathogenic bacteria 

 will be given, and from these other bacteria must be dis- 

 tinguished by the application of the methods of diagnosis 

 already detailed, or by the special methods still to be 

 described. There occur, however, from time to time as 

 contaminations of bacterial cultures, organisms of a more 

 complicated structure than the bacteria, namely fungi, and 

 therefore we shall describe a few of the typical forms of these. 

 The fungi have probably descended from the algae, or 

 both have had a common ancestor. This is shown by the 

 close resemblances in structure and development which the 

 two groups present to each other. The chief differences 

 centre round the degeneration of structure which the adoption 

 of parasitism entails on the fungi. In the algae, reproduction 

 takes place in both sexual and non-sexual ways. In the 

 former case, certain cells called gametes are set apart, and by 



