624 
TRICHOMYCETES, ACTINOMYCETES, HYPHOMYCETES 
tibial abscess and somewhat later Gilchrist^ reported a case of blasto- 
mycetic dermatitis in man. Since that time numerous similar cases 
have been recorded, a majority of them around Chicago. ^ The causa- 
tive organism (Blastomyces), has been variously grouped with the 
yeasts and with the oidia. It is usually referred to as a yeast.^ 
Morphology.— Blastomycetes, as found in the tissues, are ovoid 
or spherical cells measuring from 3 to 30 microns in diameter, the 
smaller dimension being the more common. Mycelial and hyphaeal 
forms are found in cultures, but they are rarely met with in the tissues. 
The mycelial filaments measure from 5 to 10 microns in diameter. 
The cells usually occur in groups of 15 or 20 or even more, but occa- 
sionally single organisms are met with. The variation in size with 
large groups of Blastomyces is usually very considerable. A thick 
membrane or capsule is frequently found around mature cells within 
the tissues of the body, but ascospores have not been definitely demon- 
FiG. 95. — Blastomyces — section of lung. 
strated. The Blastomyces stain with ordinary anilin dyes and they 
are Gram-negative. They are best observed unstained in hanging 
drop preparations previously treated with XaOH, which brings out 
their outline sharply and also the refractile layers of the cell membrane. 
Of particular importance is the recognition of budding, which at once 
distinguishes the organisms. The cytoplasm is granular while the 
cell as a whole possesses no flagella and is consequently non-motile; 
the granules frequently exliibit Brownian movement. 
Isolation and Culture.— The Blastomycetes grow with moderate 
luxuriance upon Loffler's blood serum and glucose agar. Initial pure 
cultures are somewhat difficult to obtain, however, chiefly because 
adventitious organisms are almost always present, which overgrow 
> Johns Hopkins Hosn. Rep., 1S96, 1, 269. 
2 See Arch. Int. Med., 1914, 13, 508, for Case Reports. 
■'' See Ricketts, Oidiomycosis (Blastomycosis) of the Skin and Its Fungi (Jour. Med. 
Res., 1901, 6, 374) for full bibliography to that date, as well as for excellent illustrations. 
