Pathogenesis 



401 



sules of the latter are distinct. It is also readily taken up by the 

 leukocytes, and may so resemble the gonococcus; and it is not al- 

 ways easy, perhaps not always possible, to distinguish it from the 

 Diplococcus intracellularis meningitidis. 



Morphology. The organism is spheric or slightly ovoid, may 

 occur singly, though usually appears in pairs or clusters. Large 

 numbers are enclosed in the leukocytes or other cells. The spheric 

 organisms have a diameter of about i M; the ovoid organisms may 

 measure as much as 1.5 by 2 ju. The relation of the cocci to the 

 cells seems to have something to do with the course of the inflam- 

 matory conditions with which they are asso- 

 cia ted. D uring the activity of the process large 

 numbers of the cocci may be free; toward its 

 close they may all be enclosed in the leukocytes. 



The organisms are not motile and they have 

 no flagella. 



Staining. The cocci stain by ordinary 

 methods, but not by Gram's method. 



Cultivation. The organism can be easily 

 cultivated, and thus differentiates itself from 

 the fastidious gonococcus. The colonies are 

 large, white, irregular in outline, elevated at 

 the center, not viscid, and grow readily at 

 room temperatures upon all the culture media, 

 the best upon blood agar-agar. The vitality 

 of the organism in culture is not great. Very 

 often transplantation made after from four to 

 six days fail to grow; and in the cultures one 

 usually finds many deeply staining, supposedly 

 living cocci, and many poorly staining, sup- 

 posedly dead organisms. 



Agar-agar. The culture in general re- 

 sembles that of Staphylococcus albus. When 

 blood is added to the agar-agar, the growth 

 is more luxuriant, whitish, and usually consists 

 of closely approximated colonies which do not 

 become confluent. 



Gelatin. This medium is not liquefied. 



Bouillon. At the end of the first day no growth seems to have 

 taken place, but at the end of the second day there is a slight cloud- 

 ing and a meager precipitate. The organism seems to maintain 

 its vitality somewhat longer in bouillon than in other culture- 

 media. 



Pathogenesis. The organism seems to be scarcely pathogenic 

 for animals. Kirchner was able to kill a guinea-pig by intrapleural 

 injection, and Neisser, who performed numerous experiments upon 

 mice, guinea-pigs, and rabbits, only once succeeded in producing a 



Fig. 145. Micrococ- 

 cus catarrhalis colonies 

 on agar (F. T. Lord; 

 photo by L. S. Brown). 



