72 BACILLUS DIPHTHERIA 



Streptococcus Pyogenes, and is often crushed out by 

 their growth. 



The free surface of the false membrane is usually 

 covered with a mixture of micro-organisms, but im- 

 mediately below this layer the B. Diphtherias often 

 occurs almost pure, lying in groups and small colonies 

 in the necrosed tissues (Fig. 67). This bacillary 

 zone is generally separated from the infiltrated 

 deeper tissue by a necrosed but microbe-free 

 stratum. 



The bacillus is a small rod-shaped, non-motile, 

 Gram-staining organism about the length of the 

 tubercle bacillus (2 to 3 /*), but somewhat thicker 

 (7 p). Frequently the organisms show a strong 

 tendency to arrange themselves parallel to one 

 another a tendency well seen in Fig. 68, which 

 represents a preparation made from the nasal secre- 

 tion of an apparently healthy child, who, however, 

 was the source of infection for several brothers and 

 sisters. 



The organisms, it will be observed, are to a very 

 large extent collected within the polynuclear cells, 

 and the photograph furnishes a good representation 

 of the phenomenon of phagocytosis. 



The bacillus, in both secretion and cultures, fre- 

 quently presents a swelling and clubbing of the ex- 



