474 



Mr. E. C. Grey. Decomposition of 



The consideration of this relationship is, however, not one of the objects of 

 the present communication. 



It is important to note that the difference in motility between strain 

 No. 1 and No. 2 is not merely one of degree but rather one of kind. It is, 

 as a matter of fact, rather difficult to decide whether No. 2 is really motile 

 at all, and only after concentrating the attention on one bacillus and 

 observing its position from time to time in relation to an adjacent organism 

 is it possible to decide that it really does exhibit a motion of translation. 

 The strain was examined very many times in cultures from 3 to 12 hours' 

 growth and at later periods, but no increase in the motility of this strain 

 was ever observed. With the strain No. 1 the appearance is entirely 

 different ; in cultures of any age from 3 to 24 hours, rapid motility is readily 

 observed. In cultures less than 9 or 10 hours' old the bacilli may be seen 

 travelling with such rapidity that it is almost impossible to follow the course 

 of any one particular bacillus. In young cultures (3 to 7 hours) the bacilli 

 may be readily seen in long threads, in which the bacilli have not had time 

 to separate. No such threads were obtained with strain No. 2. 



The highly motile typical B. coli communis (Escherich) will be referred to 

 as No. CI, and the feebly motile strain as No. CF. 



Artificial Selection of Non-gas-jproclucing Strains by Grovjth of B. coli communir 

 (Escherich) on Agar containing Sodium Chloroacetate. 



The technique of the chloroacetate method of selection has been described 

 by Penfold (1911) and has been closely followed here. It has been found, 

 however, that there is very considerable variation in the power of resistance 

 to sodium chloroacetate. and also in the appearance of the chloroacetate agar 

 plates inoculated with various strains of B. coli (Escherich). The nature of 

 the changes brought about by growth in the presence of sodium chloro- 

 acetate will be discussed in a separate communication, and it must suffice to 

 say here that the changes do not merely consist in the simple disappearance 

 of the power to produce gas from glucose, but are, rather, of such a nature 

 as to affect, to a greater or less extent, most of the enzymatic functions of 

 the cell. 



Some of the selected organisms are grown anaerobically only with great 

 difficulty, and hence their chemical products cannot be readily investigated. 

 Other strains show the property of spontaneously agglutinating and cannot, 

 therefore, be very well shown to be derived from the original organism. In 

 this work, only those selected strains which, by means of the agglutination 

 test, could be demonstrated as related to the original organisms, have been 

 employed for the examination of the decomposition products from glucose 



