ACTINOMYCETES. 283 



encountered in Boston, point to another type of parasite as 

 the causative factor in the black mycetoma. Instead of an 

 actinomyces, Wright found a true mould. He expresses 

 the opinion that the pale mycetoma is, etiologically, actino- 

 mycosis, and that the black is a hyphomycetic infection. 



The fungus encountered and isolated in pure culture 

 by Wright presented the following characteristics : As 

 obtained from the affected tissues, the mycelia under the 

 microscope appear as black or brown mulberry-like 

 masses less than one millimetre in diameter. They are 

 hard, rather brittle, and difficult to break up under the 

 cover-glass. On soaking them in a strong solution of 

 sodium hydroxide they become softened and the struct- 

 ure of the fungus-mass can be made out. Under high 

 magnifying power these masses are found to consist of 

 pigment-granules, ovoid translucent bodies, and dis- 

 tinctly branching separate hyphse. Sometimes these 

 latter exhibit dilatations or varicosities of their seg- 

 ments. The periphery of a granule shows the pres- 

 ence of club-shaped hyphse, closely set and radially 

 arranged. From such granules growth on artificial 

 culture-media may be obtained. When transferred 

 direct from the tissues to artificial media, growth in 

 every case starts from the granule about four or five 

 days after it is placed upon the culture-media. 



On solid media it first appears as delicate tufts of 

 whitish filaments. These in the course of a few days 

 increase in number and length, and, in the case of the 

 potato, form a dense whitish or pale-brown felt-work 

 having a tendency to spread widely. 



In pure cultivation it is seen as long, branching hyphse 

 with delicate transverse septa. In old forms the hyphse 

 may be swollen at the points marked by the septa, and 



