=Saccharomycetes= occur in fermenting substances, as in the fermentation of saccharine solutions. The only organism belonging to this order, which is associated with diseased conditions, is the _Sarcina Ventriculi_. This is found occasionally in the vomit or even in the urine of some persons. The =Zygophyta= occur as thread-like growths, forming a mycelium. This is composed of jointed branching tubular cells, in which minute spores are produced. Each spore, when liberated from its tube, is capable of producing another mycelium, and thus the growth spreads. The spores may be carried through the atmosphere, thus producing infection at a distance. They have an average diameter of 6 µ = about 1∕4000 inch. The following are the chief Zygophytous parasitic diseases:—=Thrush= is associated with the growth of a minute filamentous fungus, the _oidium albicans_. It is common in babies, who are improperly fed, and in old people, or in persons exhausted by any chronic disease. Small white patches collect on the tongue and neighbouring parts, and these are often followed by the formation of minute ulcers. When it occurs in children, the food must be carefully attended to, and feeding bottles frequently scalded, etc. =Ringworm= is due to the growth of a large spored or a small spored fungus (known under the names of _Microsporon Audouini_; _Trichophyton megalosporon endothrix_, _Trichophyton megalosporon ectothrix_) which attacks the skin. It is most difficult to eradicate when it occurs in hairy parts, as the growth penetrates to the roots of the hairs, and continues to live here long after it has been destroyed on the general surface of the skin. The fungus spreads on the skin in gradually enlarging circles, forming rings with a slightly raised margin. It is extremely contagious, being especially apt to spread in schools. The spores may be carried about by means of hats or bonnets, by gloves, towels, razors, and other means. The disease often remains undetected for some time; and many cases, especially where the scalp is affected, remain contagious after they have been apparently cured. The removal of ringworm, as of all other skin parasites, is effected by some local parasiticide. Prolonged treatment, including the pulling out of diseased hairs, is required for ringworm of the scalp. A special cap should be worn, when the patient mixes with others. =Favus=, or “scald-head,” is due to the growth in the skin of a minute fungus called the _Achorion Schönleinii_, which invades the same parts as those affected by ringworm, but differs in its mode of formation of spores; yellow cupped discs from 1∕4 to 1∕3 inch in diameter being produced. It is very rare in England, and almost confined to persons (especially children) who are kept in a filthy condition. It is a common and fatal disease in mice. The treatment is similar to that of ringworm.