476 



Mr. E. C. Hort. 



in these cultures is not sufficiently great to enable one to arrive with 

 certainty at a correct interpretation of the different forms seen. 



By the use, however, of broth + 20 to phenolphthalein, and by sub-culture 

 from this to agar or to MacKonkey's medium, thence back again to ordinary 

 broth, +10 to phenolphthalein, I found that a great increase in size can 

 with patience be obtained, still giving the classical cultural, fermentative, 

 and serological reactions. This was particularly the case with the B. typhosus, 

 with the B. Shiga-Kruse, with the B. T of Hiss, and with the coliform 

 organism examined. In the case of both the Paratyphoids, and of the 

 B. dysenterice of Flexner, a considerable increase in size was also obtained 

 by using these acid cultures, though so far I have not succeeded in obtaining 

 the same increase as in the case of the other organisms mentioned. 



Before going through the drawings, for which I am mainly responsible, 

 and the photographs, for which Mr. Martin Duncan's skill and tireless 

 enthusiasm are solely responsible, it is necessary briefly to deal with the 

 possibility that many of the types of organism shown are merely involution 

 forms. 



That this is not the case is shown by the following considerations : — 



1. The " aberrant " forms shown are young, freely growing, freely 

 dividing organisms. By the use of the Congo-red method, the relative 

 age of organisms can be fairly accurately gauged, owing to the fact that 

 young organisms are brightly refringent, older organisms being faint or 

 dark in colour. 



2. In the case of the B. typhosus, the B. Y of Hiss, the B. of Shiga-Kruse, 

 and the coliform organism, the growth in broth +20 to phenolphthalein 

 was no less free and vigorous than in broth + 10 to phenolphthalein, and it 

 was in these that the largest and most " aberrant " types of organism 

 occurred in the greatest numbers. Moreover, in broth +60 to phenol- 

 phthalein the degree of turbidity produced by the B. typhosus and by the 

 organism of the coliform group was greatly in excess of that produced by 

 these organisms in standard broth, + 10 to phenolphthalein. 



3. These " aberrant " types maintained their " aberrancy " for several sub- 

 cultures when put back into broth + 10 to phenolphthalein, even when the 

 latter was inoculated direct with single colonies from MacKonkey's medium. 



4. They were seen in small numbers, if carefully searched for, in ordinary 

 cultures in broth, + 10 to phenolphthalein, which had never been inoculated 

 from broth of a higher acid titre. 



This was also true of single colonies on MacKonkey's medium, or on agar, 

 that had not at any time been derived from incubated broth cultures, but had 

 been isolated direct from the feces or urine of carriers. 



