290 TEXT-BOOK OF BACTERIOLOGY. 



bacilli at breeding- temperature on boiled potatoes or growing 

 them on agar-agar. 



These facts rendered the opinion very plausible that in this case 

 we had genuine spores. But there were certain doubts as to this 

 opinion. The shining bodies in the rods lacked the finely-defined, 

 regular form we are accustomed to see in the spores; they could 

 not be stained in the usual way differently from the other cell con- 

 tents; they were extremely sensitive to the influence of high tem- 

 peratures and were surely destroyed by heating to 60 C. for about 

 ten minutes, thus but slightly complying with the requisites of a 

 real spore. 



Recent investigations, especially by Buchner and Schiller, have 

 proved beyond doubt that the presumptive spores have no such 

 significance. Buchner ascertained that the shining oval bodies 

 lying in the ends of the rods (the " pole-grains ") and the spots ap- 

 pearing as bright gaps by staining are two altogether different 

 things. 



The former consist of condensed protoplasm, are even highly 

 accessible to coloring substances, absorb them before all other parts 

 of the bacillus, and are to be looked upon as structures connected 

 with a degeneration of the cell i.e., involution forms. They de- 

 velop abundantly, therefore, only under conditions unfavorable to 

 the growth of the bacilli ; for instance, by exclusion of oxygen or on 

 acid media, especially on sour potatoes. When we artificially im- 

 part to the latter an alkaline reaction the pole-grains disappear, 

 and the active multiplication and energetic growth of the micro- 

 organisms become manifest by the circumstance that only quite 

 short, single rods, bvit no threads tending to division, can still be 

 observed. 



The unstained gaps, on the other hand, are produced by the 

 circumstance that (during the drying of the bacteria on the cover- 

 glass or under the influence of color solutions) the bacterial proto- 

 plasm becomes detached and contracts from the membrane at 

 these places a process occurring mostly in the ends, but frequently 

 also in the centre of the rods. 



As Buchner has shown and Schiller has confirmed, the bacilli 

 provided with " spores " are, therefore, less resistant than those 

 "free from spores," and the power of resisting desiccation is a 

 property inherent to these bacteria. 



The typhus bacillus belongs to those varieties which can thrive 

 in the absence of oxygen, as well as under its free access. But its 

 development in the latter case is much more perfect and energetic. 



The typhus bacilli in cover-glass preparations are stained with- 



