554 The Philippine Journal of Science ims 



the third, 1 out of 123. The other single-cell cultures as well as 

 the parent culture render maltose alkaline. 



2. The nonfermenting type produces secondary colonies con- 

 sisting of normal and involution cells, either of which may 

 develop acid- or alkaline-producing cultures. An ordinary trans- 

 fer from a secondary colony, including many cells of both sorts, 

 gives an acid-forming culture. 



3. Selection from the acid-producing type failed to produce 

 any but similar types, and selection from the alkaline-producing 

 type gave only alkaline, provided secondary colonies were not 

 chosen. 



4. Mixed cultures, consisting of an equal number of cells of 

 each type, showed that the two types may exist side by side 

 through from 10 to 15 daily transfers, but with a tendency for the 

 acid to outstrip the alkaline. 



5. Transfer in maltose broth gave no increase in the acid- 

 producing power except in old cultures. 



6. Growth in various substances other than maltose failed to 

 alter materially the characteristics of the two types. 



7. In a specific serum, the two types showed approximately 

 the same agglutination. 



8. A permanent new race, characterized by morphological 

 peculiarities, was obtained by the selection of an aberrant cell 

 from a culture of dysentery of the Shiga-Kruse type. 



Since the special technique used in this research has been 

 described in other publications,*'* only the portion having to do 

 with the making of one-cell cultures in series will be given 

 here. A large cover glass (about 38 by 65 millimeters) is 

 carefully cleaned, sterilized, and placed on the isolation chamber 

 in the usual manner. Lines are ruled on the upper side with 

 India ink or wax pencil, as shown in the illustration. Then, 

 with a sterile pipette, bent at the tip, droplets of sterile broth 

 about 2 millimeters in diameter are made on the undersurface 

 of the cover, with a long drop a toward the open end of the 

 box and a second large drop b near the other end. 



Into a large drop a a small portion of actively growing culture 

 is transferred by a loop or pipette. The chamber is now placed 

 on the stage of the microscope, a fine-pointed pipette of the 

 type used in isolation adjusted, and a considerable number of 

 bacilli in medium dilution taken into the pipette from a. The 



" See reference, under note 1. A complete description of the pipette 

 technique and its various applications is in preparation, and will be 

 published in a subsequent number of this Journal. 



