PUS-PRODUCING MICROORGANISMS 91 



name Staphylococcus epidermidis albus given. It does 

 not produce disease, but is of constant annoyance in 

 making blood cultures. Another staphylococcus pro- 

 duces a lemon-yellow color. 



These staphylococci are very widely distributed and 

 seem to be almost constantly upon the surfaces of the 

 body, upon skin, in the sebaceous and sweat gland 

 openings, on the mucous membranes. For this reason 

 they are of great surgical importance and may originate, 

 in a postoperative infection, from the patient, physician, 

 or nurse. Their rather high resistance to disinfection 

 demands great care in surgical technic. The com- 

 monest conditions in which these cocci are implicated 

 are pimples, boils, carbuncles, lymph-gland swellings, 

 osteomyelitis and endocarditis. 



Vaccines and Opsonins. The use of killed bacteria to 

 produce an increased resistance against an existing 

 infection has already been discussed. This method of 

 treatment is particularly suitable for infections with 

 staphylococci. The procedure is about as follows: 

 Cultures are made from the diseased part, grown in 

 large quantities on laboratory media, washed off, 

 suspended in physiological salt solution and heated to 

 a temperature which will kill their disease-producing 

 properties and stop their multiplication, but will not 

 alter their peculiar chemical composition. The number 

 of bacteria are then counted by a special technic and 

 hypodermic injections are made of definite numbers. 

 The size of dose and rate of increase of number injected 

 are controlled by what is called the opsonic index. The 

 opsonins, as will be remembered, are substances in the 

 blood which make the bacteria suitable for ingestion by 



