MICRO-ORGAXIXMS BELONGING TO THE HIGHER BACTERIA 429 



Loeffler blood serum seems to be the most suitable medium for cul- 

 tures. The growth on this medium is more rapid and abundant than 

 on any of the other media tried. 



On plain agar and glycerin agar the growth is the same as on blood 

 serum, but is less rapidly developed. 



In bouillon the growth is slow and takes place only at the surface 

 and on the sides of the tube. The bouillon remains perfectly clear 

 and no pellicle or scum develops on the surface. If the tube is not 

 disturbed or jarred, minute white tufts are seen clinging to the surface 

 of the glass. But if the tube is shaken even slightly they sink slowly to 

 the bottom, forming a white, fluffy layer. These growths when undis- 

 turbed resemble minute balls of thistle-down. The yellow color is not 

 apparent even in the mass at the bottom of the tube. 



It is strictly aerobic. In sealed tubes a very scant growth is obtained, 

 but when deprived of oxygen absolutely no growth can be detected, 

 although life is preserved for long periods. Cultures from a tube kept 

 for two months without oxygen, and showing no sign of growth, devel- 

 oped rapidly when exposed to the air. 



Morphology. The relative thickness of the threads varies some- 

 what in different parts of the same individual branching organism, and 

 considerably in specimens taken from different culture media. If the 

 growth is rapid and luxuriant, the threads are thicker than in specimens 

 taken from growths on less suitable media. For instance, when grown 

 on blood serum the threads are comparatively thick and coarse, but 

 those growing in bouillon are very slender and delicate. The main 

 trunk also is often thicker than the branches. When unstained they 

 are homogeneous gray threads, without any appearance of a central 

 canal or double-contoured wall. There is never any segmentation of 

 the threads. When properly stained there is always a distinct beading 

 or fragmentation of the protoplasm, but overstating with fuchsin 

 produces rather coarse, evenly red rods. The branching is irregular 

 and without symmetry, and the branches are placed at a wide angle, 

 very nearly, and sometimes quite, at right angles. This is best seen 

 in specimens taken from liquid media. The irregularly stellate arrange- 

 ment of the branches, which was observed by Eppinger in his original 

 specimen, is often seen in young organisms floated out from a liquid 

 medium. Eppinger considered this form sufficiently characteristic to 

 warrant the term asteroides to distinguish the species. But terms like 

 asteroides and arborescens do not sufficiently distinguish the species 

 of a genus which is characterized by more or less tree-like branching, 

 and so far no satisfactory nomenclature has been adopted. 



Spore Formation. On examining the deep-orange or red-colored 

 growth upon potato, one is surprised to find that the threads have 

 entirely disappeared, and that the specimen consists of moderately 

 large cocci. In very young cultures upon potato both threads and 

 cocci are found, but the relation between them cannot be seen in smears 

 prepared in the ordinary way. In older cultures no trace of the thread 

 can be found, unless some fine granular matter may represent them 



