392 BACTERIOLOGY. 



being the cause of disease in plants and animals lead the 

 investigators of that period to make thorough studies of 

 such affections. This led to the discovery during the fourth 

 decade of a large number of moulds which were shown to be 

 pathogenic for man, animals and plants. 



Several of these fungous diseases may be briefly men- 

 tioned. The blight on potato leaves is due to the Perono- 

 spora infestans. The mildew of grapes and other plants is 

 due to various species of Oidium. The ergot of rye and 

 other grasses is due to the Claviceps purpurea. The smut on 

 corn and other plants is due to several species of the fun- 

 gus Ustilago. Bunt, the blight which attacks the grain of 

 wheat and spelt forming a black fetid powder or mass of 

 spores, is due to another mould, the Tilletia. The rust or 

 mildew on grains is due to various species of the Puccinia. 



The parasitic mould which can be seen on dead flies is 

 known as the Empusa muscce. The silk- worm disease, mus- 

 cardine, as stated above is due to the Botrytis Bassiana. 



The skin affection in man, known as Herpes, is due to 

 a group of fungi, commonly designated as Tricophyton ton- 

 surans, which, by some is placed in the Botrytis group. The 

 fungus of thrush in children is known as the Monilia Candida 

 and by some is placed in the Oidium group. Favus is a skin 

 disease of man due to the Achorion Schdnleinii. Similar af- 

 fections are known to exist among birds, mice and other 

 animals. Another cutaneous disease, pityriasis is ascribed 

 to the fungus Microsporon furfur which, however, has not as 

 yet been successfully cultivated. 



Streptotrices. 



Under this name are included certain saprophytic, and, 

 at times, pathogenic organisms which show some resem- 

 blance to the moulds as well as to the bacteria. In other 

 words, they are to be considered as intermediate forms. 



