CHAPTER II. 



MOULDS ; FILAMENTOUS FUNGI ; HYPHOMYCES. 



BESIDES being the exciting cause of some diseases, especi- 

 ally those of the skin, moulds are frequently met in the 

 laboratory in the way of culture contaminations. 



Filamentous fungi is an infinitely better name than moulds ; 

 and is also, in a measure, descriptive of their appearance and 

 method of reproduction. Their growths are often very beau- 

 tiful, especially when pigments are formed. A filamentous 

 fungus consists of thread-like cells or filaments which do not 

 contain chlorophyl and which have an apical growth. They 

 interlace very freely and grow luxuriantly, often forming 

 dense, heavy, felt-like membranes. The growth is usually 

 very dry, but occasionally the surface of the membrane is 

 studded with minute dew-drop-like pearls ; or the -moisture 

 may be diffused, giving the growth the appearance of a crust 

 or scutulum. The threads forming the growth are termed 

 hyphce, and the growing or vegetative portion of the fungus 

 is the mycelium. Arising from the mycelium is the fruit- 

 bearer or sporangium. This carries the spores or conidia. 

 From the spores are developed new hyphae and new fungi. 



These fungi are classified according to the structural differ- 

 ence in the sporangium. Several thousand different kinds 

 of moulds have been described, only a small number of 

 which possess clinical importance. They are divided also 

 into saprophytes and parasites. The majority of mould fungi 

 are saprophytes, and are not met with in man. The parasitic 

 fungi may be the cause of disease in the human organism. 

 This parasitism may be purely accidental, although a few 

 fungi are really obligative parasites. 



Moulds as a class are strict aerobes, and require an acid 

 medium for their development. That is one reason why they 



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