92 THE UNIVERSITY SCIENCE BULLETIN. 



would seem that for comparison milk agar plates might equally 

 well be substituted and perhaps prove equally reliable. In 

 either proteolysis or milk agar plates or hemolysis, it is ap- 

 parently important to have an optimum and known hydrogen- 

 ion concentration in the medium. This is very easily a source 

 of discrepancies. The blackening of lead acetate agar might 

 also be worth including. 



There does not seem to be any uniform correlation between 

 the property of proteolysis of milk agar plates and hemolysis 

 on blood agar plates. . 



Apparently most staphylococci from the animal body are 

 hemolytic. 



Contrary to frequent statements in the literature, human 

 blood seemed to be superior to either rabbit or sheep blood. 



As might well be expected, hydrogen-ion determinations 

 show that staphylococci can rightly be grouped into at least 

 two groups with respect to some one indicator such as methyl 

 red, and into more groups if desired. I do not know that this 

 is consistent or will prove of value. 



Acknowledgment is hereby made to two members of the department of 

 bacteriology of the University of Kansas, Prof. N. P. Sherwood and 

 Miss Cornelia M. Downs, for many valuable suggestions and criticisms of 

 my work. 



BIBLIOGRAPHY. 



Jordan. General Bacteriology, 1908, p. 161'. 



1. Pasteur. Bull, de 1 Acad. de. Med., 1880, 9, p. 447. 



2. Ogston. Brit. Med. Jour., 1881, 1, p. 369. 



3. Becker. Deut. Med. Wehnschr, 1883, 9, p. 665. 



4. RoSENBACH. Mikroorganismen bei d. Wundinfekhonskronkheiten, 



Weisbaden, 1884. 



5. WiNSLow, C. E. A., knd Winslow, A. R. The Systematic Relation- 



ship of the Coccacese, 1908. 



6. Dudgeon, L. S. The Differentiation of the Staphylococci. Journal 



of Pathology and Bacteriology, 1908, 12, 242. 



7. Winslow, C. E. A., Rothberg, W., and Parsons, E. Q. Notes on the 



Classification of the White and Orange Staphylococci. Journal of 

 Bacteriology, 1920, vol. V, p. 145. 



8. Cole. Practical Physiological Chemistry, p. 14. 



9. Clark, W. M., and Lubs, H. A. Journal of Bacteriology, 197, li, I; 



The Colorimetric Determination of Hydrogen Ion Concentration 

 and its Application in Bacteriology. 



