58 MEDICAL BACTERIOLOGY 



disclose the nature of a staphylococcus infection; it does not indicate which 

 staphylococcus is the offender; to determine this cultures on agar or gelatin 

 must be made and chromogenesis observed. 



When infection of the blood is suspected a conspicuous vein is sought, usually 

 at the elbow, the skin overlying the vein is asepticized, a sterile needle is thrust 

 into the vein, and from 2 to 10 cc. of blood withdrawn with a sterile glass syringe. 

 The blood is immediately ejected into a flask containing 200 cc. of sterile bouillon. 

 The flask is shaken and then incubated at 37C. for i or 2 days. If growth ap- 

 pears a loop full of the bouillon is smeared on a slide, stained and examined; 

 subcultures on agar and gelatin may be made. 



When obtaining material from an inflamed surface, pus, blood or urine to 

 examine for staphylococci, the common presence of staphylococci upon the sur- 

 face of the body must be remembered and scrupulous precaution observed to 

 prevent contamination, otherwise misleading findings may be made. 



Opsonic index and complement fixation tests have a limited value in the 

 diagnosis of obscure staphylococcus infections, but are seldom employed. 



SERUM AND VACCINE THERAPY 



Sera have been prepared to combat staphylococcus infections, but their 

 value is slight. Vaccines or bacterins fortify or elevate natural immunity and 

 so modify, limit and curtail infections, in favorable cases. 



