NON-SPECIFIC PYOGENIC COCCI 193 



grouped irregularly. The diameter of the cells is about 0.7 to 

 0.9 u., rarely larger. It stains well with ordinary anilin dyes and 

 is gram-positive. 



Isolation and Culture. Micrococcus aureus may be frequently 

 secured in pure culture by making cultures directly from a fistula 

 or other suppurating focus, first cleansing the outer portion and 

 securing material on a sterile platinum needle. In general it is 

 best, however, to plate out the drop of pus obtained in this way. 

 This is not only important in preventing contamination, but 

 hi order to diagnose, mixed infections, especially in isolations made 

 for the purpose of preparing autogenic vaccines. The organism 

 grows well in all the common laboratory media. The colonies 

 upon gelatin appear as disks with smooth, definite edges, and with 

 granular, dark interior. Within a few days the colony sinks in a 

 cup of liquid. The liquid is cloudy, with a golden-yellow sediment. 

 The growth on agar is abundant, shining, and well circumscribed. 

 Upon the potato the growth is luxuriant, and the orange pigment 

 is produced here in greatest abundance. Bouillon is clouded. 

 Milk is curdled with a slight acid reaction, and the curd is eventu- 

 ally digested. 



Physiology. A study of the physiologic characters of this 

 organism makes it apparent that there are many races of which 

 account must be taken. It has not been satisfactorily demon- 

 strated, however, that there is any relationship between these 

 variations and pathogenicity. 



Pigment Production. An orange-yellow pigment is produced. 



Fermentation. A slight power to produce acid in milk has been 

 noted. No gas is produced. Nitrates are reduced to nitrites. 

 A proteolytic enzyme which digests casein is produced in milk. 

 Gelatinase is found in gelatin. Rennin and maltase have been 

 demonstrated. 



Relation to Oxygen. The organism is aerobic and facultative 

 anaerobic. 



Vitality. There is a marked resistance to desiccation, although 

 it is not probable that the organism can remain alive for very long 

 periods in this condition. Cultures upon media will remain alive 

 for months. The optimum growth temperature is blood-heat, 

 although growth is good at room-temperatures and below. The 



13 



