bays: classifying staphylococci. 77 



tion, pigmentation, hemolysis, proteolysis on milk agar plates, 

 liquefaction of gelatin, blackening of lead acetate agar, and 

 the determining of limiting hydrogen ion concentrations of 

 each strain in dextrose broth. I hoped to see if there was a 

 correlation of any of these with source and pathogenicity. 



In order to do this, I have subdivided this work under six 

 headings, as follows : 



1. Assuming as Dudgeon that staphylococci seemed to be one species 

 and disregarding the characteristic of pigment production and liquefac- 

 tion of gelatin, is it possible to subdivide staphylococci in general upon 

 a basis of fermentation of carbohydrates. In determining data for this 

 question, I have asked myself to note the following questions : Does the 

 classification by fermentation reaction offer any correlation with pig- 

 ment production, liquefaction of gelatin, with pathogenicity, with source? 

 and. Is there a correlation between rapidity of fermentation and of pig- 

 ment production and pathogenicity as suggested by Winslow? 



2. After studying staphylococci as a whole from the standpoint of 

 fermentation reactions, it was next decided to assume pigmentation as 

 the primary differentiation into subgroups of white, yellow and orange 

 staphylococci and attempt the subdivision of each of these by means of 

 fermentation reaction. The borderline yellows and orange pigment pro- 

 ducers were placed in their respective groups of yellow or orange. 



3. The next step was to assume, as before, pigmentation as a pri- 

 mary differentiation into white, yellow and orange staphylococci then to 

 attempt a subdivision of each of these by means of blood agar plates, 

 placing the hemolizers and nonhemolizers in separate groups as has been 

 done for streptococci, these were again subdivided upon the basis of fer- 

 mentation reactions. In the work on hemolysis, a comparative study was 

 made using different kinds of blood, such as rabbit, sheep and human. 



4. A similar study of staphylococci in which pigmentation was made 

 use of for primary subdivision of each group, subdivided again in ac- 

 cordance with the ability of various strains in that group to produce 

 proteolysis upon milk agar plates. This gave proteolytic and nonproteoly- 

 tic subdivision. These were further divided upon the basis of fermenta- 

 tion. It was necessary to study the reationship between reaction of 

 media and degree of proteolysis in obtaining data for this work. 



5. To study the ability of the various staphylococci to produce hy- 

 drogen sulphide, all staphylococci were first inoculated into both one per 

 cent peptone broth agar containing lead acetate, and three per cent pep- 

 tone broth agar containing lead acetate to see whether there was any 

 correlation between the blackening of lead acetate and any other char- 

 acteristics. I might say there was noted apparently a correlation be- 

 tween pathogenicity and blackening of three per cent peptone lead acetate 

 agar. 



6. Lastly, it was thought worth while to determine the limiting 

 hydrogen ion concentrations of all these various staphylococci in dextrose 

 dipotassium phosphate broth to see whether there exist high and low 



