148 WINSLOW, ROTHBERG AND PARSONS 



The 22 cultures isolated from the hands were obtained by 

 rinsing the surface of the hands in sterile water and plating 

 on glucose agar, from which characteristic white and orange 

 colonies were fished. 



Of the 54 strains which came from sources other than the 

 human body 39 were obtained from the air by exposing glucose 

 agar plates in the offices and workrooms of the American Museum, 

 in the New York Subway, and in the streets and parks of New 

 York City. Thirteen were isolated from dust collected in the 

 same general localities, one strain was isolated from a sample 

 of butter and one from water. 



In analyzing our results we have divided our strains from 

 the standpoint of source into these three main groups, 104 

 isolated from pathogenic conditions, 22 from the hands and 54 

 from sources outside the human body. 



CHROMOGENESIS 



The chromogenic power of our 185 strains was determined 

 as follows : Each strain was cultivated on a nutrient agar streak 

 for fourteen days at 20°C. A portion of the growth was then 

 spread with a platinum loop over white paper (Whatman No. 2) 

 and allowed to dry in the air. The hue and tint were then 

 matched against the frontispiece of the Systematic Relation- 

 ships of the Coccaceae (by C.-E.A. and A. R. Winslow). The 

 determinations of chromogenesis were made for the whole series 

 on two different occasions about six months apart. 



Four strains originally isolated as orange pigment producers 

 proved on examination to belong to the group of the red chromo- 

 genic cocci (Rhodococcus) and were excluded from subsequent 

 consideration. One strain gave inconsistent results on the two 

 series of tests being recorded as orange on the first occasion and 

 white on the second. This strain was also excluded from our 

 series leaving 180 strains for detailed study. 



These 180 strains divided themselves naturally into two very 

 clearly marked groups, as did the cocci studied by the Winslows. 

 One hundred of them were of the Albococcus type giving a pig- 

 ment which could be matched in the Light Lemon Yellow, 



