THE PATHOGENIC FUNGI 097 



On broth they usually form a thick membrane which spreads over the 

 surface, but if the fragment planted sinks it develops 'only a delicate mesh 

 of filaments in the bottom. On potato the growth is less vigorous and 

 often moist. Gelatin is liquefied by most strains. Glucose and mannite are 

 usually completely consumed but no gas is formed and the medium is not 

 acidified. Lactose, saccharose and maltose are less favorable to growth. 

 Like many other fungi the dermatophytes grow well on the simpler synthetic 

 media without peptone or protein, if glucose be added. 



The optimum reaction is somewhat more acid than that for bacteria, 

 about P H 7.0; but they develop readily throughout a range of reaction from 

 4.0 to 8 and above. Although obligate aerobes, they will grow feebly with 

 scanty oxygen supply as in the depth of a broth culture. They develop well 

 at room temperature and most species also in the incubator. 



Morphology. Morphologically as has been said there is little 

 that characterizes the ringworm fungi as a group. In the infected 

 hairs or skin, they appear as masses of spores or as filaments, the 

 latter often consisting of chains of spore-like cells. In culture the 

 growth is made up of branching hyphae which are always septate 

 but may be coarse or delicate, straight or crooked, cylindrical or 

 irregularly bulging. Under favorable conditions most species pro- 

 duce conidia. Chlamydospores are far more common and arthro- 

 spores are also found. From the common molds which they some- 

 what 'resemble these parasites are distinguished by the absence of 

 ascospores or of the specialized conidiophores such as are found in 

 the aspergilli and penicillii. These characteristics do not, how- 

 ever, serve to distinguish them from other hyphomycetes. 



Individual species do develop in culture peculiar spores and 

 mycelial structures which help to distinguish them. The following 

 are some to which Sabouraud has given descriptive names : 



Morphological Definitions. Clubs. These are swollen mycelial tips which 

 vary greatly in size. They are not markedly differentiated from the hyphae 

 which bear them but when occurring in great numbers as in the achorion 

 of favus they present a striking and characteristic appearance. 



Fuseaux. These are large elongated chambered bodies considered as 

 chlamydospores by some, by others as specialized conidia. Sabouraud applies 

 this name to two different types, one a lenticular spore with a tapering 

 pointed tip and thick doubly contoured wall, covered with warty or hairy 

 outgrowths, the other a blunt club-shaped spore with thin smooth walls. Both 

 are divided into segments by parallel transverse septa. 



Conidia. These are irregular in shape, size, and arrangement. In the 



