74 RELATIONSHIPS OF THE COCCACE^ 



6. Amount of acid produced in 2 per cent lactose broth. 

 Same conditions as under 5. 



7. Formation of nitrites in nitrate solution. Ob- 

 served in a series of 10 tubes grown for 7 days at 20 

 degrees. 



8. Formation of free ammonia in nitrate solution. 

 Same method as under 7. 



9. Comparative growth and color production, after 

 14 days on agar streak at 20 degrees and 37 degrees 

 respectively. Recorded as 1 (much more vigorous at 

 20 degrees); 2 (more vigorous at 20 degrees); 3 (equal); 

 4 (more vigorous at 37 degrees); or 5 (much more vigorous 

 at 37 degrees). 



10. Chromo genesis. Hue and chroma of pigment pro- 

 duced on agar at 20 degrees after 14 days, determined 

 by comparison with color scheme as described above. 



11. Depth in cm. of gelatin liquefaction in tube of 

 10 mm. diameter after 30 days at 20 degrees. 



It would be well to extend this series of tests by study 

 of the cell-grouping in broth, motility, fission on the agar 

 block, fermentation of saccharose, effect of acid and alka- 

 lin media, and the thermal death-point. Data in regard 

 to agglutination reactions might throw light on the 

 systematic relations of many members of the group. 

 Investigations as to the power of cocci to break up 

 rafnnose, inulin, mannite, dulcite, and many other car- 

 bohydrate media have proved of significance in the 

 hands of Gordon, Houston, Andrewes and Horder, and 



