FUNGAL PAfeASITES ON ANIMALS I7I 



man, generally infecting the hairs of the scalp in 

 children. 



Other fungal diseases of the skin or mucous mem- 

 branes are pityriasis, due to Microsporon furfur, which 

 forms a spore-producing mycelium on the skin, 

 especially in phthisical patients ; and " thrush," caused 

 by a fungus which has a septate mycelium forming 

 white patches on the tongue and on the mucous mem- 

 brance of the throat, mostly in children, and also 

 producing spores, round or oval in shape. 



" Blastomycosis " of the lung or kidney is caused 

 by single cells, which form endogenous spores, like 

 yeast, and may also produce a mycelium in artificial 

 cultures. This kind of fungus is also found on the 

 skin, often following a slight wound, and causing 

 suppuration (pus formation). Another fungus which 

 inhabits the lung cavities is Aspergillus fumigatus, 

 which forms a spore-bearing mycelium and spreads 

 into the bronchioles (small branching air tubes of the 

 lungs). This form is generally, but not always, found 

 in company with disease-producing bacteria. Asper- 

 gillus also occurs in the external ear. 



Saprolegnia and Fish Disease. — A good example of a 

 facultative parasite is Saprolegnia, which lives sapro- 

 phytically on the dead bodies or parts of animals and 

 plants that have fallen into or died in the water, but 

 which also attacks living aquatic animals, such as 

 insects, fish and amphibia. A spore germinating on 

 the body of an aquatic insect, for instance, sends out 

 a tube which penetrates the tissues of the insect, and 

 branches to form a mycelium which ramifies through- 

 out the body. This, of course, causes the death of 

 the insect, and the fungus lives saprophytically for a 

 time on the dead tissues. Eventually thick branches 



