This has already been mentioned as connected with the presence of a fungus. It occurs chiefly in the mouths of young unhealthy children, but is also occasionally seen in emaciated adults, as in diabetes. The normal secretion of the mouth is alkaline, but in this disease it becomes acid, which may perhaps be the reason that the fungus develops. The mucous membrane is found beset with small white spots, which look like little bits of white curd on the surface. These patches are, however, adherent, and on removing them the mucous membrane beneath will be found red and bleeding. The white patch consists of epithelium united into a membrane by the fungus, the oidium albicans (Fig. 161, p. 375). It consists of branching threads composed of elongated cells placed end to end and sometimes losing themselves in masses of spores. The aphthous patches frequently extend from the mouth downwards to the pharynx and oesophagus.