Apeil 30j 1915] 



SCIENCE 



661 



dead bacteria present is at a minimum. More- 

 over, in those eases where they are present, they 

 are just as indicative of the past history of the 

 milt as are living bacteria. Very variable condi- 

 tions in regard to the clumping of bacteria in 

 milk have been observed. In many cases the bac- 

 teria occur largely as single individuals or as 

 clumps of twos, in other cases the milk is filled 

 Ti'ith compact clumps which could not be separated 

 by any known methods of plating. Where thick 

 cream is present and the right types of bacteria 

 occur, colonies may be formed much like those 

 found on agar or gelatin. These variations in 

 clumping produce very variable effects on the 

 plate count which would be unrecognizable where 

 this technique is used alone. 



The Standard Method of Determining Nitrate de- 

 duction: Robert S. Breed. 



Attention is drawn to the fact, more or less gen- 

 erally known, that the Committee on Standard 

 Methods of Bacterial Water Analysis have inad- 

 vertently given us two different formulae for ni- 

 trate broth in each of the two editions of the 

 Standard Methods which have been published. All 

 of the formula call for one gram of peptone per 

 liter, but the amount of nitrate varies. Altogether 

 three different amounts are mentioned, namely, 2 

 grams, 0.2 gram and 0.02 gram per liter. 



The committee's statement that the nitrate re- 

 duction test is sometimes quite erratic has been ex- 

 plained for some cases at least by tests which have 

 been carried out at the New York State Experi- 

 ment Station. Fifty cultures of bacilli of the colon 

 group, isolated from a sewage-polluted stream, 

 gave very erratic results with the standard broth 

 which contained 0.2 gram of nitrate per liter, 

 scarcely one third of the cultures giving results 

 which showed a clear reduction. However, as 

 soon as the amount of peptone was increased to 

 five grams per liter, all of the cultures gave posi- 

 tive reactions for all tests. 



On the other hand, tests for thirty cultures of 

 bacilli of the subtilis group isolated from soil 

 gave unmistakably positive or unmistakably nega- 

 tive results in a number of tests in the same ni- 

 trate broth. Varying the amount of peptone from 

 one to five grams per liter had no influence on the 

 results. Twenty of these cultures reduced ni- 

 trates, while ten failed to do so. In all cases there 

 was a vigorous growth of the bacilli in every tube. 

 Tests with a single culture of an unknown soil 

 organism showed, however, that it was necessary to 

 be cautious in recommending that the amount of 

 peptone in the standard broth be increased. This 



organism showed a condition the exact reverse of 

 that .iust reported for the colon bacillus. Positive 

 results were obtained in all cases where 1 gram of 

 peptone per liter was used, while increasing the 

 amount of peptone caused erratic and finally nega- 

 tive results when as much as 5 grams per liter was 

 used. 



Evidently nitrate reduction should be tested in 

 a broth in which the organism to be tested will 

 grow vigorously. Irregular results are open to 

 suspicion in all cases. No one broth can be used 

 for all organisms and suitable broths must be de- 

 vised to fit each group of organisms. It is par- 

 ticularly unfortunate to report an organism as 

 lacking the power to reduce nitrates when it fails 

 to reduce them in a broth in which it does not 

 grow. Either such results should not be reported 

 at all or reported as doubtful. 



Starch Agar, a New Culture Medium for the 



Gonococcus : Edward B. Vedder. 



Starch agar is a beef -infusion agar (1.5 per 

 cent.) without salt or peptone, to which is added 

 3.0 per cent, of starch, preferably corn -starch, 

 though potato starch or tapioca will serve. Reac- 

 tion, 0.2-0.5 acid to phenolphthalein. The advan- 

 tages of this medium are as follows: 



1. The gonococcus grows very freely on this 

 medium, producing a heavy growth suitable for 

 the preparation of vaccines or antigens. 



2. When the tubes are sealed with paraffine, 

 cultures jemain alive upon this medium for a long 

 time, at least 20 days, so that transfers of stock 

 cultures may be safely made every two weeks in- 

 stead of every three or four days, as is customary 

 when other media are used. 



3. This medium may be melted and used in 

 pour plates in order to isolate gonococci in pure 

 culture from gonorrheal pus. 



4. Some other organisms that are usually culti- 

 vated with considerable difSculty grow well on 

 this medium; i. e., certain strains of tubercle ba- 

 cilli, the lepra bacillus (Duval), and freshly iso- 

 lated streptococci and pneumocoeei. 



5. The medium is suitable for routine use as 

 practically all organisms grow as well or better on 

 this medium as on plain agar. 



The great simplicity of preparation of this 

 medium and its many advantages appear to indi- 

 cate that it may be very useful to many workers, 



A New and Sapid Method for the Isolation and 

 Cultivation of Tubercle Bacilli Directly from 

 the Sputum and Feces, with the Aid of Sodium 

 Sydrate and Gentian Violet-egg-meat Juice 

 Media: S. A. Petrofp. 



