SYMBIOSIS. 49 



we examine water, milk, or the intestinal contents in 

 health or disease, we always find many varieties simulta- 

 neously present. This mixture certainly appears to us as a 

 pure accident, but upon closer study it is found that also 

 in the domain of bacteriology there are synergists 

 (mutual or one-sided aid) and antagonists (mutually 

 injurious, or one to the other). Nencki speaks of symbi- 

 osis and enantobiosis. 



Experimentally, Garre has demonstrated the antagonism by inocu- 

 lating various bacteria simultaneously in streaks upon gelatin plates 

 as parallel or intersecting lines. It then appears that many varieties 

 thrive but slightly or not at all if another variety grows in the 

 immediate neighborhood. The antagonism is very often only on one 

 side; for example, the Bact. putidum grows very well if inoculated 

 between closely placed, well-developed streaks of staphylococci ; on 

 the contrary, the Micr. pyogenes does not grow if inoculated between 

 luxuriantly developed cultures of Bact. putidum, and if the two are 

 simultaneously inoculated in alternating streaks, the former grows 

 very slightly (Garre, " Correspondenzbl. f. Schweizer Aerzte," 1887, 

 387). 



Another way of showing antagonism is by preparing plates of gela- 

 tin or agar (for liquefying varieties), which, while liquid, are inocu- 

 lated with equal quantities of two different varieties of bacteria; often 

 only one variety will develop ( Lewek, C. B. VII, 107) . 



A third way of carrying out the investigation is to inoculate simul- 

 taneously the same fluid nutrient medium with two varieties, and, 

 later, determine microscopically or by plates which is triumphant in 

 the battle. This is what is commonly observed when a cause of fer- 

 mentation is abundantly introduced into a suitable nutrient medium ; 

 the contaminating bacteria are overgrown and sometimes perish. 



From these observations the practical conclusion is 

 reached that for determining the number of bacteria in a ma- 

 terial the colonies in the plates must not be very thick, and also 

 that for the isolation of definite varieties, thin plates are neces- 

 sary ; for example, if one wishes to isolate the Bact. 

 Pfliigeri from abundant Bact. putidum. In an area of 

 several millimeters about each putidum colony no Bact. 

 Pfliigeri will grow (K. B. Lehmann). 



Finally, in the animal body bacteria may counteract 

 each other as antagonists ; as Emmerich has pointed out, 

 animals infected with anthrax may be saved by subsequent 

 infection with Streptococcus pyogenes. Literature by 

 Muhlmann (C. B. xv, 895). 



Symbiosis of bacteria appears to be of more practical 



