319 



individuals, after some time return to the latter, to take in a new provision of oxygen. 

 Outside the accumulation, near the edge of the cover-glass, where the pression of 

 oxygen increases, the nuniber of bacteria diminishes quickly, together with the mobi- 

 lity of the remaining ones. At the edge itself all is in complete rest, and no motion 

 sets in when the surrounding is freed from oxygen. Still I have no reason to consider 

 the resting individuals as dead; I even think they function as an «oxygen filtrum«, 

 thus protecting the more inwanlly swarming. 



If some grains of fibrine are introduced into preparations of which the figures 

 of respiration are being studied, and if placed at c. a. 25" C. in a »humid rooni«, a 

 considerable increase of bacteria may readiiy occur. U'atching the process micros- 

 and macroscopically, we find the growth alniost exclusively limited to the accumulation 

 parallel to the edge, which accumulation grows more and more dense by the increase 

 of the spores, whilst the central part continues as clear as at first. Consequently, it 

 may be taken for granted that B. septiciis requires oxygen for its growth, as well as 

 for its mobility. 



On this occasion I wish to correct a mistake in my description of Spirilhtm 

 desulfuricans. I there stated erroneously ^ ) that Spirillion tenue, which is typical for 

 microaërophily as to mobility, is also microaërophilous with regard to growth, so that, 

 when sown in a fit culture mass, it shows its maximum growth, not at the surface, 

 hut at a certain distance below it. 



This has proved to repose on »trophotropy«, signifying that growth is more fa- 

 vored by the influence of the food than by the oxygen. It occurs only when a bad 

 culture ground is taken for the e.xperiment, and it is by the aërophily of the growing 

 spirilli that it must be e.xplained. For the intense growth will cause at the surface a 

 rapid exhaustion, so that, if no abundance of food is present, and if the food can only 

 come up slowly from the depth by the process of dififusion to the place of consumption, 

 then, not the surface itself, hut a deeper layer will, under the joined action of oxygen 

 and food, be most favorably situated for growth and increase. Thus in facf. Spiriüiun 

 tenue is aërophilous as to growth and microaërophilous as to mobility. 



Beside to this peculiar form of »trophotropy« in the growth, one has to pay atten- 

 tion, when studying the figures of respiration, to a phenomenon of alniost the same 

 nature with respect to the mobility, and which may be called »trophotaxis«. Tt con- 

 sists in the accumulation of the mobile microbes, which are more attracted by the 

 food than by the oxygen, not in the meniscus and at the edge of the preparation, but 

 at some distance. I observed this in an aerobic species, which T have called BaciUiis 

 perlibratus, where trophotaxis may become so strong, that microaërophily is mimicked, 

 and was erroneously described by me as such-). 



With abundant food, however, nothing is to be seen of these phenoinena, so th.it 

 by attentive observation microaërophily may always distinctly be recognised. 



I now return to the anaërobes of the putrefaction of proteids, and in particular 

 to the second important form. the skatolbactery. Of this polymorphous form 1 exa- 

 niined, as alreadv said, material closely allied to the tetanus-bacillus, which material 

 is strictly anaërobic, and perhaps ought to be considered as the most characteristic 



') .^rchives Xéerlandaiscs, T. 29, pag. 272. 



■-) Centralblatt fiir Bactcriolnuit-. Bd. 14, pag. 8.30. 1893. 



