540 PATHOGENIC FUNGI 



a great variety of differentiating characters emerge. Thus the 

 organism may tend to spread in a fairly thin layer over the 

 medium and sometimes may present the appearance of successive 

 concentric rings of growth ; on the other hand the colony may 

 be heaped up in the centre as a projecting knob, or there may 

 be a central depression round which the heaping up may occur. 

 Sometimes there are ridges or folds radiating from the centre 

 of the colony, often presenting a geometrical arrangement but 

 sometimes having an irregularly convoluted appearance. The 

 surface may have a general woolly appearance or may give the 

 impression of being covered with fine powder. Sometimes the 

 surface formation is moist and slimy-looking. These appear- 

 ances are exemplified in Figs. 163, 164, 167. When colour is 

 produced it develops with age. An important point is the occur- 

 rence of pleomorphism. Thus a sub-culture frequently presents 

 characters different from those of the parent growth, or on a 

 coloured colony colourless points .may appear which may 

 maintain the non-pigmented character when sub-cultured. The 

 evidence at present is that these are cases of true pleomorphism 

 and are not due to contaminations. On media presenting large 

 surfaces the colonies assume a correspondingly large size and 

 growth usually goes on until the whole medium is exhausted. 



THRUSH (German, Spoor; French, Muguet}. 



This condition, which is most common in children, chiefly 

 affects the tongue and fauces, and may extend into the oesophagus. 

 It is characterised by white patches largely composed of fungoid 

 growth, which cause slight erythema and catarrh of the sub- 

 jacent epithelium. A similar condition may occur in the vagina, 

 and a few cases of generalised affection with abscesses in the 

 solid organs have been recorded. The organism closely resembles 

 the Oospora (Oidium) lactis (vide p. 532), very frequently found 

 in milk, and has been called Oidium albicans or Monilia Candida. 

 It occurs in two chief varieties a large-spored and a small-spored 

 form, the former being the more frequent. Both in the tissues 

 and in cultures the chief elements are double-contoured, septate 

 mycelial threads, the elements being of varying sizes, and 

 round or oval spores (in the large-spored type 5-6 //. long and 

 4 /u. broad). The fungus grows readily on artificial media, 

 especially those containing beerwort (p. 52), and while some 

 varieties liquefy gelatin, others do not. In the case of the latter, 

 the superficial colonies on gelatin are granular with peripheral 

 feathery extensions, while the deep colonies are rounder and 



