1 66 



C.-E. A. WiNSLOw AND Anne F. Rogers 



the average of two blank controls. No determination was made of 

 the rate of acid production as distinguished from this total final 

 acidity, though such observations might be of much interest. 



Action upon nitrates. — Data with regard to the reduction of nitrates 

 by the cocci are extremely meager, the presence or absence of this 

 character being recorded in very few of the published descrip- 

 tions. It seems, however, to have a fair degree of definiteness, 

 and we have included it as a qualitative test in our routine. 

 Each organism was inoculated into a series of lo tubes of standard 

 nitrate solution. After seven days' growth at 20° the tubes were 

 tested for nitrites and ammonia by the regular method prescribed 

 by the Committee on Standard Methods (1905). The test for nitrates 

 was omitted after it was found that all the cultures, out of a con- 

 siderable series tested, gave positive results, without exception. 

 The results of the tests for nitrites and ammonia are expressed in 

 the number of tubes which gave positive results, out of the 10 which 

 were tested. In view of the fair constancy of the reaction as observed, 

 we regret that this test was not made quantitative. 



Production oj indol. — A preliminary examination of some 50 cul- 

 tures showed no production of indol in any case, and a study of the 

 literature of the cocci indicates that this property is very rare, if it 

 ever occurs, in this group. It was therefore omitted from our 

 routine. 



Inhibition oj growth by acidity and alkalinity 0} media. — This 

 character is of considerable importance and warrants careful study, 

 but it is obviously a difficult property to observe in a large series of 

 cultures, and we have not attempted to use it in the present investi- 

 gation. A preliminary examination of t,t, cultures, the results of 

 which are shown in the table, indicated that i per cent is the opti- 

 mum acidity for a majority of these organisms, and that an excess 

 of acidity over this amount is more generally fatal than an alkahne 

 medium. 



Optimum Reaction for Growth and Color Proddction. 

 number of organisms. 



