WHITE AND ORANGE STAPHYLOCOCCI 149 



Light Cadmium Yellow and Medium Cadmium Yellow of the 

 Winslow's chart, usually in the three lightest chromas. The 

 other 80 were of the Aurococcus type, their pigment being matched 

 by the Orange Yellow and Cadmium Orange hues, usually in the 

 darker chromas. 



So far as pigment production alone is concerned, these two 

 types are clearly and definitely to be distinguished from each 

 other. 



Of the 104 strains isolated from pathological conditions 53 

 were of the white and 51 of the orange type. Of the cultures 

 from the hands 16 were white and 6 orange and of the air and 

 dust strains, 31 were white and 23 orange. No correlation 

 appears, therefore, to exist between chromogenesis and habitat. 



GRAM STAIN 



The Gram stain was made by the method described in the 

 Systematic Relationships of the Coccaceae. Agar cultures 

 which had been incubated for twenty-four to forty-eight hours 

 at 20° and 37°C. respectively were treated with anilin-oil- 

 gentian violet for one and one-half minutes; with Gram's solu- 

 tion for one and one-half minutes; with 95 per cent alcohol for 

 three minutes; and counterstained with Bismarck Brown for 

 one-half minute. Altogether we repeated the whole series five 

 separate times. 



The cocci exhibit a somewhat variable reaction to the Gram 

 stain but of our 180 strains 136 were consistently positive on all 

 five occasions, 39 were generally positive but gave negative results 

 on 1 or 2 out of the five trials and 5 were consistently negative. 

 These 5 strains had no other special characteristics in common 

 except that all were gelatin liquefiers. 



LIQUEFACTION OF GELATIN 



The property of gelatin liquefaction was studied in the fol- 

 lowing manner. Each strain was first grown for twenty-four 

 hours at 37°C. in nutrient broth containing 1 per cent gelatin 

 and one loopful of this culture was then spread over the surface 



