154 



FUNGI: NON-PATHOGENIC AND PATHOGENIC. 



whatever. Involution forms are occasionally encountered and 

 appear as shrunken empty capsules of irregular contour. . No 



mycelial development 

 has ever been found 

 in the lesions. In 

 artificial conditions, 

 such as afforded by 

 various cultural media, 

 theorganisms undergo 

 considerable mo'difica- 

 tions. Three types of 

 cell growth can be dis- 

 tinguished : ( i ) round 

 or oval budding cells 

 much smaller than 

 those seen in the tis- 

 sues; (2) segmented, 

 branching mycelial 



FIG. 64. -Blastomyces dermatitidis (Gilchrist) : the threads, occasionally 



sporulating(?) form in an abscess cavity, showing eruption buciclinp; ' ( 3) aerial 

 of spores (?) through a rent in the cell membrane X 1000. ' 



[By the kind permission of Dr. T. Caspar Gilchrist.] hyphae bearing CO- 



nidia. 



Cultural Characters. Ricketts in a comparative study divides 

 the organisms into three groups: (i) those growing upon 

 slanted agar or beerwort agar with a moist, smooth, whitish, 

 pasty surface, and usually appearing upon the inoculated medium 

 within 24-48 hours; (2) those having a granular, semi-moist 

 surface, slightly elevated, and incorporated with the medium 

 - after a time the surface of the growth becomes markedly 

 plicated ; (3) those at first scarcely rising above the surface, deli- 

 cate, feathery, radiate, semi-moist, and of a gray-white colour, 

 closely incorporated with the medium, and after several days' 

 growth 'developing aerial hyphae with conidia, in some cases, 

 resembling the growth of a mould, and in the others being dry 

 and as if dusted with flour. The two latter groups require from 

 2-10 days after the medium has been inoculated before growth 

 develops. Gilchrist is of the opinion that these last two groups 

 of Ricketts are identical, as he has observed both types of growth 

 occurring in the same culture at different times. In liquid media 

 the organisms of the first type grow at the bottom of the tube 



