March 7, 1902.] 



SCIENCE. 



373 



bouillon, and in bouiUon containing one 

 per cent, dextrose, lactose and saccharose. 

 The degree of motility and the indol reac- 

 tion were also considered. 



The purpose of these examinations was 

 to find the extent to which varieties of this 

 bacillus exist normally in the intestines of 

 both different individuals of the same spe- 

 cies and of different species of animals. 

 This was to determine if the many varie- 

 ties of the colon bacillus which have been 

 described from polluted water, soil and 

 from lesions of various lands in man and 

 animals, have their natural existence in 

 the generally supposed normal habitat of 

 this species of bacteria. The results 

 showed no pronounced variation in the 

 morphology or the cultural characters of 

 these bacilli from different sources on gela- 

 tin, agar, potato and bouillon. The action 

 on the sugars, milk and the indol produc- 

 tion differed somewhat. The two varie- 

 ties, A and B, described by Smith in 1896 

 were found. The A variety, i. e., those that 

 ferment, with gas production, dextrose, lac- 

 tose and saccharose, and the B variety, 

 i. e., those that do not ferment saccharose, 

 were found in about equal numbers in each 

 species of animals. Other varieties did not 

 appear, although there were slight varia- 

 tions in the qviantity of gas, the gas for- 

 mula, and the time required for the milk to 

 coagulate. . The cultures from different 

 colonies from the same plates did not show 

 any appreciable difference except in one 

 instance, from a dog. The plate cultures 

 made from one dog did not develop colo- 

 nies resembling those of B. coli communis. 

 The cultures from dogs Avere more virulent 

 for guinea-pigs than those from the other 

 species of animals. The action on the sug- 

 ars was considered of the most differen- 

 tial importance. 



Color Standards for Recording the Results 

 of the Nitrite and Indol Tests: C. E. A. 



WiNSLOw, Massachusetts Institute of 



Technology, Boston, Mass. 



In studying the effect of certain exter- 

 nal conditions on the reactions of the Ba- 

 cillus coli communis, need was felt of 

 some definite standard by which to meas- 

 ure somewhat quantitatively the capacity 

 for nitrite and indol production. It is true 

 that even when the conditions of the ex- 

 periment— the composition of the medium, 

 the amount and character of the culture 

 used for inoculation, and the time allowed 

 for the development of the reaction — are 

 rigidly controlled, striking variations some- 

 times appear. The laws of such varia- 

 tions can, however, only be properly stud- 

 ied when their sequence is made manifest 

 by definite comparable standards. 



The .use of a color standard for measur- 

 ing the reduction of nitrate and the forma- 

 tion of indol obviously suggests itself as 

 simpler and more practical than any other 

 method. Up to the point at which a pre- 

 cipitate forms in the nitrite reaction, the 

 depth of color in both cases may be con- 

 sidered as roughly proportional to the 

 amount of the end product formed by the 

 bacteria in a given time. The problem for 

 the bacteriologist is then to select from the 

 numerous schemes of color values, prepared 

 for artistic and educational purposes, that 

 one best suited for the matching of the re- 

 action in question. 



The most rational system of color stand- 

 ards is that prepared by Milton Bradley, of 

 Springfield, Mass., based on pure spectral 

 colors of known wave-length. It is issued in 

 the form of a small booklet, and by cutting 

 out and pasting to a card the colors between 

 red and yellow, orange and their tints, a 

 chart is obtained on which the color of the 

 indol reaction produced by B. coli com- 

 munis can be readily matched. The hue is 

 read by holding the tube parallel to a white 

 surface and looking through it at right 

 angles, while the matching color on the 



