INFECTION WITH SARCINA TETRAGENA 397 



result from the invasion of the tissues by the organism now 

 to be described, viz., sarcina tetragena. 



This organism was discovered by Gaflky, and was subse- 

 quently described by Koch in the account of his experiments 

 upon tuberculosis. It is often present in the saliva of 

 healthy individuals and is commonly present in the sputum 

 of tuberculous patients. Koch found it very frequently in 

 the pulmonary cavities of phthisical patients. It, however, 

 plays no part in the etiology of tuberculosis. It is principally 

 of historic interest, being of little pathogenic significance. 



It is a small round coccus of about 1m transverse diam- 

 eter. It is seen as single cells, joined in pairs, and in 

 threes; but its most conspicuous grouping is in fours, from 

 which arrangement it takes its name. In preparations made 

 from cultures of this organism it is not rare to find single 

 bodies which are much larger than the other individuals in 

 the field. Close inspection reveals them to be cells in the 

 initial stage of division into twos and fours. A peculiarity 

 of this organism is that the cells are bound together by a 

 transparent gelatinous mass. 



When cultivated artificially it grows very slowly. 



Upon gelatin plates the colonies appear as round, sharply 

 circumscribed, punctiform masses which are slightly elevated 

 above the surface of the surrounding medium. Under a 

 low magnifying power they are seen to be slightly granular 

 and to present a more or less glassy lustre. 



The colonies increase but little in size after the third or 

 fourth day. If cultivated as stab-cultures in gelatin, there 

 appears upon the surface at the point of inoculation a cir- 

 cumscribed white point, slightly elevated above the surface 

 and limited to the immediate neighborhood of the point 

 of inoculation. Down the needle-track the growth is not 



