XI, B, 6 Wade: Cultivation of a Pathogenic Fungus 271 



Multiplication. — Having attained their maximum size, the 

 entire-cell forms sometimes undergo a simple segmentation, 

 during which the nuclear mass becomes irregular in outline 

 (fig. 10) and is broken up to form botryoid groups of from 5 

 to 10 small, round, basic forms of different sizes, the individuals 

 of which are ultimately liberated by dissolution of the proto- 

 plasm (figs. 8 and 14, c). There is no regularity in the number 

 of small forms produced. The segmented parasite in fig. 14 

 is of unusually large diameter. These groups are not numer- 

 ous and have been found only in the superficial, more active 

 areas. More common than this segmentation is multiplication 

 by the simple fission of a nuclear body into parts, equal or 

 unequal. This may occur even in the smaller parasites (14, h) 

 and occasionally is seen even among the phagocytized bodies. 



In the active foci the free-lying forms are particularly nu- 

 merous, occurring in blood and lymph spaces and among the 

 tissue cells. Infrequently they are seen, as in figs. 13 and 14, 

 invading areas of the epidermis without cellular reaction. 



As the parasites do not stain differentially, their recogni- 

 tion both in tissue sections and in smear preparations is de- 

 pendent in part upon morphology, the outline of the nuclear 

 body usually being strikingly clear-cut, and particularly upon 

 their intensity of staining. In view of their frequently close 

 resemblance to lymphoid and plasma cells and of the intensity 

 with which injured tissue-cell nuclei stain, this is at best an 

 uncertain criterion. The more solid bodies retain Gram's stain 

 more intensely than do tissue nuclei, but a clear differentiation 

 is not possible. There has nowhere been found evidence of cap- 

 sule formation, the material which develops about the free-lying 

 forms being distinctly protoplasmic in its staining reaction. 



CULTURAL FEATURES 



Slight multiplication of this organism in cultures on solid 

 media seems always to occur, provided tissue elements are pres- 

 ent, but on all except a few media it soon ceases. In smears 

 from such cultures, which appear sterile, the forms that result 

 from this brief multiplication may be easily passed over without 

 recognition, particularly after staining by Gram's method (figs. 

 15, 16, and 17). Many of the appearances which it may assume 

 are so dissimilar that some of the forms might well pass unre- 

 cognized in the search for others. The principal modes of devel- 

 opment as they have been observed will be described separately. 



DEVELOPMENT OF PARASITIC FORMS ON BLOOD-SMEARED AGAR 



If material obtained by scraping an incised, active lesion be 



