104 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



the tubercle bacillus, will not grow on these plates ; the strepto- 

 coccus and the bacillus of glanders will grow feebly, if at all. 



In a day or two longer the plates will, in some cases, be found 

 to have undergone a decided change. If liquefying organisms are 

 present the colonies will soon become depressed below the general 

 surface of the medium, and will be surrounded by haloes which 

 consist of liquefied gelatin. This will happen with the staphylo- 

 cocci and the B. pyocyaneus ; not with the streptococci, the 

 typhoid bacillus, nor with the B. coli. 



The bacillus of blue pus can readily be distinguished from the 

 staphylococci by its morphological appearance (it is a slender rod), 

 and by the fact that the gelatin round the colony is coloured blue 

 or bluish-green, the growth itself being nearly white. 



Interpretation of Results. 



. The chief practical value of the bacteriological examination of 

 pus is derived from the fact that if specific vaccine treatment (on 

 Wright's system) is to be used, the vaccine must be prepared from 

 the organism which is causing the disease. If a patient is suffer- 

 ing from a staphylococcic lesion, it is not much use inoculating him 

 for pneumococci, or vice versa. I have seen and obtained such 

 excellent results in some cases by treatment of this nature that 

 very little doubt remains in my mind that the method is one which 

 will be widely used in the future. Except for this the results 

 obtained by a study of the bacteria in pus are more of scientific 

 interest than of practical importance. It is the situation of the 

 collection of pus rather than the bacteria causing it which 

 influences treatment and prognosis. A list of the more important 

 results which are produced by the chief pyogenic bacteria may be 

 of interest. 



Staphylococci are the chief producers of localized suppuration in 

 the skin — such, for instance, as that which occurs in boils, 

 carbuncles, impetigo, folliculitis, etc. They may cause abscesses 

 in any part of the body, and may also give rise to general infec- 

 tions, ulcerative endocarditis, etc., though this is rare. 



It is in the localized skin affections of staphylococcic origin 

 especially that good results are obtainable by specific vaccination, 

 and a cure may often be obtained in cases which are very intract- 

 able by other methods. 



Streptococci usually cause spreading inflammation of the type of 

 erysipelas or cellulitis. They are common causes of osteomyelitis 



