HYPHOMYCETES 271 



probably around a decayed tooth, or the crypts of the tonsils, or 

 some slight abrasion. Both in cattle and in pigs fragments of 

 grain have been found in the soft tissues of the mouth embedded 

 in an actinomycotic growth, and since there is a certain amount of 

 evidence that grain is the natural habitat of the organism, infection 

 has been thought to occur from this source. Other authorities 

 maintain that the parasite is present in normal mouths and that 

 penetration depends only on a damaged mucous surface and a 

 certain degree of susceptibility on the part of the host. 



Mycetoma (Madura Foot) . The disease resembles actinomy- 

 cosis both as regards the character of the lesions and the occurrence 

 of the parasite in the form of granules. They are nevertheless un- 

 doubtedly distinct. Mycetoma usually appears as a purulent 

 inflammation of the foot, occasionally of the hand or other part 

 of the body. A small swelling first appears which gradually 

 enlarges, and in the center of the new tissue there occurs a purulent 

 softening followed by ulceration. Enlargement and distortion 

 of the affected part and frequently necrosis of the bones occur. 

 Within the softened tissue the small granular bodies may be seen, 

 yellowish pink in color or almost black like grains of gunpowder. 

 It is thought by some observers that the yellow form is actinomy- 

 cosis and that the black variety is caused by a member of the hy- 

 phomycetes group. Clinically the two forms of the disease are 

 identical. 



HYPHOMYCETES 



The molds and trichobacteria closely resemble each other in 

 that both have a branching, thread-like growth. The life history 

 of the former, however, is much more complicated than that of 

 the latter. 



The growth of the hyphomycetes is characterized by a mass 

 of tubular, branched filaments termed hypha, which interlace one 

 within the other, forming a more or less web-like structure known 

 as the mycelium. In the lower forms, the phycomycetes, each 

 hypha is a single sometimes branched cell except when reproductive 

 organs occur, whereas in the higher forms, the my corny cetes, the 



