The four varieties of human infections caused by fungi whose mycelium or conidia or both are dark colored, are described and discussed under the headings of superficial, cutaneous, subcutaneous and systemic mycoses. Three diseases, black piedra, tinea nigra and mycotic keratitis, were considered in the superficial category. Their etiologic agents, respectively 4 and 17 in number were briefly described in terms of their clinical manifestations, in vivo and in vitro morphology. The subcutaneous mycoses with dematiaceous etiologic agents are chromoblastomycosis and phaeohyphomycosis. The former is considered to be caused by any one of six moulds classified in the genera Cladophialophora, Cladosporium, Fonsecaea, Phialophora and Rhinocladiella. The fungi incriminated as agents of phaeohyphomycosis, currently total 32. The fundamental differences between chromoblastomycosis and phaeohyphomycosis lies in the tissue form assumed by their respective etiologic agents. In chromoblastomycosis, the parasites occur as large, muriform, thick-walled dematiaceous cells. In phaeohyphomycosis the fungi basically occur as dark walled septate, hyphal elements. The mycetomas with black granules are known to be caused by 9 species of moulds classified in 6 genera. Within limits, the identity of a given black grained mycetoma can be deduced through the characteristics of the granules.

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As regards the pathogenesis of pulmonary aspergilloma, it has generally been approved that fungus grows as a saprophyte in preexisting cavity of tuberculous or bronchiectatic origin to form a intracavitary fungus ball, and no invasion of fungi occurs into the surrounding tissue. Detailed histological study of lung specimens resected from 13 patients with aspergilloma gave us, however, a result fairly different from this theory. Pericavitary or distant invasion of fungi was found in all cases, mostly in cavitary or bronchial wall and lymphoid follicle, rarely in lymphnode capsule or blood vessel wall. We found two types of tissue reaction: acute exudative or chronic productive, the latter being characterized by foreign body giant cell granuloma. Allergy and immunity might play a certain role in the progress of disease, as on one hand fungi were few and shrunken within the lesion, on the other remarkable was the tissue reaction such as proliferation of lymphoid follicle, together with positive serum precipitin test and increased immunoglobulin. Aforementioned histological study and analysis of special cases led us to the assumption that initial focus of fungal infection might be central part of bronchial tree, destructing lung tissue peripherally with cavity formation by antigen-antibody reaction and tumorous growth in situ acting as a check-valve. This hypothesis is based on the knowledge of the primary type of aspergilloma, but may be in part applicable to the secondary one.

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In this experiment, some environmental and nutritional factors influencing the dimorphism of some dermatophytes and dematiaceous fungi were examined. The formation of arthrospores in mycelial strains of Trichophyton mentagrophytes and T. rubrum was induced by growing the cultures under conditions of increased carbon dioxide tension or on Sabouraud's glucose liquid medium to which blood was added. T. mentagrophytes grew on an amino acid synthetic medium which resembled the composition of amino acids in hair. In this medium, in continuously agitated culture, numerous spherical cells appeared, which resembled the spores in infected hairs. When Fonsecaea pedrosoi and Phialophora dermatitidis were cultured on Sabouraud's glucose liquid media to which blood had been added, and in continuously agitated conditions, sclerotic cells were formed. However, the most suitable medium which produced the tissue phase sclerotic cells was glucose cysteine blood liquid medium (8% glucose, 1% cysteine, 10% blood) and in this medium numerous spherical cells and sclerotic cells were formed. In cultures of P. verrucosa and P. gougerotii, only a few sclerotic cells appeared.

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