154 C.-E. A. WiNSLow AND Anne F. Rogers 



The grouping is somewhat influenced by the age of the culture 

 and by the kind of medium on which it has grown. Even the same 

 culture will show wide variation from the typical arrangement of the 

 elements. For instance, streptococci occur singly, in pairs, chains, 

 and small masses; but the most frequent arrangement, and that ob- 

 tained under the most favorable conditions (in liquid media), is in 

 chains. Again, sarcinae occur singly, in pairs, and in small masses 

 as well as in packets, yet the typical form is the sarcina-packet. 

 Cocci grown on Nahrstoff regularly occur in plates, and usually cap- 

 sulated ones. 



In a number of preliminary studies we compared the groupings 

 of the same cultures in various media and under various conditions, 

 examining cultures of different ages, from nutrient broth, sugar 

 broth, peptone solution, hay infusions, nutrient agar, and gelatin, 

 and acid and alkaline gelatin. Cultures more than two weeks old 

 showed abnormalities both in the individual cell and in its groupings. 

 With this exception, the differences produced were very slight. The 

 only constant effect of the medium upon grouping which was apparent 

 was a more distinct development of chains in liquid cultures. Organ- 

 isms which appear as long chains in fresh broth cultures may show 

 only short chains with irregular groups on solid media. In the pres- 

 ent study we have omitted the broth morphology for lack of time, 

 and have recorded the grouping only as apparent on the agar streak. 



The streaks used were never more than three days old, and the 

 grouping was observed after staining lightly with methylene blue and 

 mounting in cedar oil. Too heavy staining may introduce a serious 

 error by making packets of small sarcinae appear like large single 

 cells. These observations on the culture stained with methylene 

 blue were controlled by careful observations of the slides prepared 

 for the study of the Gram stain, as noted later. 



We have distinguished two main groupings only by this method 

 of examination. The occurrence of packets marks one, and the ab- 

 sence of packets the other, group. In the first group occur the 

 streptococci, which produce pairs, long chains, and irregular groups; 

 and the micrococci, which show pairs, short chains, fours, and 

 irregular groups; while the sarcinse include organisms which 

 produce fours, irregular groups, and packets, as well as those 



