102 MORPHOLOGIC VARIATION 



mucoid in consistency. In liquid media there is produced a diffuse 

 turbidity; after some time a slight pellicle appears. Gelatine is 

 rapidly liquefied, but egg, blood serum, and casein are not digested. 

 No indol is formed. None of the common sugars are fermented. 

 The organism grows best on slightly alkaline media and is sharply 

 inhibited at pH 6.4. It seemed to grow equally well at temperatures 

 between 30° and 37°. 



Although various bacteriologists, notably Harris and Wade, have 

 noted the occurrence of saprophytic chromogenic diphtheriod bacilli, 

 which are common and widely distributed, these organisms have not 

 been thoroughly studied. I have found in the literature but one 

 producing a red pigment which has been adequately described and 

 named. This was reported by Hoag as "Bacillus X", and named 

 by Morse B. hoagii, which was changed to Corynebacterium hoagii 

 by Eberson. The organism here described differs markedly from 

 C. hoagii, however, in the unusually large size of the cells, the 

 deeper color, the liquefaction of gelatine, and the failure to ferment 

 dextrose and sucrose. While it grew very readily when first isolated 

 on all sorts of media, after a few years subcultivation it gradually 

 gave a scantier growth and finally died. Since the type culture 

 is therefore not available, I hesitate to name it. 



The rate of growth, length of cells, and number of metachromatic 

 granules in the cells have been determined from a series of agar 

 slant cultures inoculated from a forty-eight-hour old agar culture, 

 following the technique described in Chapter III. Measurements 

 of cell length were made from Congo red slides projected at a mag- 

 nification of 3,000 X. The granules were counted from slides stained 

 by Ponder's method with toluidine blue; and for purposes of correla- 

 tion between number of granules and size of cells the length of 

 the cells was also determined from these latter slides by means 

 of a camera lucida and dividers, the magnification being 1,500 X. 



The general character of the morphologic variations observed 

 can be seen in Figure 30, which presents a series of camera lucida 

 drawings from cultures of different ages. These were made from 

 cultures on dextrose agar, in which medium the changes in the 

 appearance of the cells are more pronounced than on ordinary agar 

 which was used for quantitative study; but the cell variations are 



