942 



THE PLEUROPNEUMONIA GROUP OF ORGANISMS 



majority of bizarre forms described by previous observers (see Lediugham 1933, 

 Turner 1935, Tang et al. 1935) were not essential morphological stages of growth, 

 but were either myelin forms or the result of distortion of the plastic elements 

 of the organism. Agreement, however, has not yet been reached on the true 

 morphology and mode of development of the pleuropneumonia organism, and we 

 shall therefore give (a) one account based on the older methods of examination 

 of slide preparations by transmitted light on a dark ground or by the staining 

 of impression films, and (6) another based on the more recent methods of examina- 

 tion of the organisms in situ, either by reflected light on a dark ground or by 

 fixation and staining. 



(a) By Older MetJiods of Examination.— At the risk of undue simplification, we 





,-.//^-^%^^' 



Fig. 228. — Organism of Pleuropneumonia. 



Stage of ramification, showing nodes of protoplasmic 

 condensation which form the starting-point for the 

 outgrowth of fresh filaments. Dark-ground illumin- 

 ation (X 1114). (After Tang e< al) 



Fig. 229. — Organism of 



Pleuropneumonia. 



Stage of chain formation, showing 

 condensation of protoplasm at 

 multiple points of filament. 

 Giemsa. (x 1640). (After Tang 

 et al.) 



shall follow Tang and his colleagues (1935) in describing five morphological stages 

 in the growth of this organism, (a) Granular stage. Small granules, coccoid, 

 diplococcoid, and cocco-bacillary bodies are seen, usually 0-15-04 [x in diameter. 

 Turner refers to them as " conidioids." They stain deeply with Giemsa, and 

 may be regarded as a resting stage (Fig. 224). (6) Filamentous stage. On inocula- 

 tion into a fresh medium the granular bodies grow into spheroids about 0-4-0-8 fj, 

 in diameter, and develop on their periphery one or more spherical buds (Figs. 225, 

 226). These gradually move away from the parent body, but remain attached 

 to it by a filament (Fig. 227). In old strains this filament is usually very short, 

 and resembles with its terminal bud a sporing tetanus bacillus. In freshly isolated 

 strains, however, enormously long filaments develop, sometimes crossing several 

 fields of the microscope. EndomyceUal protoplasmic streaming is often notice- 



