2Q6 CLINICAL BACTERIOLOGY AND H/EMATOLOGY 



a strong subject. The polynuclears and endothelial cells 

 become more and more scanty, and lymphocytes make their 

 appearance in increasing numbers. The discovery of these 

 cells in a septic exudate is a good sign; the discovery of the 

 pathogenic organism mainly or entirely within the cells is 

 another. 



(b) The process may pass on to suppuration. In this case 

 the endothelial cells become less and less abundant, and the 

 polynuclears become more numerous and undergo the various 

 forms of degeneration described above (Plate IX., Fig. 3). 



CRYPTOGENIC PLEURISY, POSSIBLY DUE TO TRUE RHEU- 

 MATISM. In this case the predominating cell is the active 

 endothelial cell in various stages of fatty degeneration, and 

 in addition there is a comparatively small number of all the 

 leucocytes in approximately the same proportions as in the 

 blood, and a few red corpuscles. The exudate is sterile. 

 These appearances are found in the very rare cases of true 

 rheumatic pleurisy, and may be regarded as a good sign, in 

 that they do not indicate a tuberculous or septic origin 

 (Plate X., Fig. i). 



PLEURITIC EXUDATES DUE TO MALIGNANT DISEASE. The 

 appearances vary, and a definite diagnosis cannot always be 

 made. There is no criterion by which an isolated malignant 

 cell can be distinguished from an active endothelial cell. In 

 some cases, however, the masses of cells, which can be seen 

 to be solid and several cells thick* occur in the exudate mixed 

 with red corpuscles and a few leucocytes. These cells are 

 variable in size, usually stain deeply, and often have a well- 

 marked nucleolus. In the figure shown (which comes from 

 the ascitic fluid in a case of carcinoma of the ovary) the resem- 

 blance to an alveolus of carcinoma as seen in a section is 

 very distinct (Fig. 55). 



In other cases, and much more frequently, these masses 

 are absent, and their place is taken by large endothelial cells 

 (often many times larger than a red corpuscle), which can be 

 seen in a wet preparation to be in various stages of fatty and 

 other forms of degeneration, and which in dry preparations 

 are found to be extensively vacuolated (Plate X., Fig. 3), and 

 often contain ingested red corpuscles. These may be 



As shown by focussing up and down whilst examining a wet specimen, 

 so as to obtain a series of " optical sections." 



