ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
337 
of the micro-organisms themselves and not the effect of a symbiosis, in 
a second memoir studies the physiological aspects of the work of the 
microbes of these nodosities, viz. the effect of air, the influence of the 
richness of the media in combined nitrogen and in saccharose on the 
fixation of free nitrogen, behaviour of the microbe to mineral nitrogen, 
and the action of the roots of the Leguminosae on the free forms of the 
microbes. 
In a third memoir the author deals with his observations on the mor- 
phology of the microbe. Both under natural conditions and on artificial 
media the bacilli are very polymorphic, presenting themselves under 
the forms of coccobacilli, filaments, branching forms, endosporous, and 
oosporous forms. Sometimes the colonies are composed of motile ele- 
ments. Mostly, however, they are motionless. 
While the bacilli freshly removed from the tubercles appear to possess 
the power of reproducing new tubercles, yet they lose this property in 
time ; and though one form or variety of the microbe is unable to produce 
the tubercles, this result may be arrived at by the co-operation of two 
forms. 
Effect of Monochromatic Light on Bacterial Development. * — 
Herren Beck and Schultz examined the action and effect of monochro- 
matic light on various bacteria, chiefly chromogenic. The bacteria were 
simultaneously exposed to the action of sunlight and diffused daylight, 
and were also protected from light. Monochromatic light was not found 
to possess an inhibitory nor a germicidal action, though occasionally it 
had some effect on the production of pigment. Diffused daylight was 
favourable to pigment formation. Direct sunlight was injurious to pig- 
ment production and to bacterial growth. Rontgen rays had no influence 
on the growth or power of forming pigment of the microbes tested. 
Production of Sulphuretted Hydrogen, Xndol, and Mercaptan by 
Bacteria, j — Herr M. Morris demonstrated the production of sulphuretted 
hydrogen by bacteria on a medium composed of agar and sugar of lead, 
in the proportion of 1 litre of agar to 1 grm. of sugar of lead, or as 1000 
to 1. On this lead-agar bacteria grow well ; the only precaution neces- 
sary is to make a deep puncture, as the surface growth does not show 
the reaction well owing to oxidation. 
The following species were found to form sulphuretted hydrogen 
very freely : — typhoid, glanders, Staphylococcus aureus , Proteus vulgaris , 
and P. mirahilis. 
The statement of Petri and Maassen, to the effect that almost all 
bacteria form sulphuretted hydrogen in media containing much pepton, 
was not confirmed for anthrax, mycoides, and subtilis. On the whole 
the author’s results agree pretty well with those of Stagnitta-Balistreri. 
Indol was copiously produced by mouse septicaemia and by B. coli 
anindolicum ; less strongly by typhoid, swine plague, riolaceus, blue 
milk, pyocyaneus , anthrax, yellow sarcina, and a yeast. Experiments 
with B. coli communis showed that the amount of indol produced was 
proportionate on the one hand to the time, and on the other to the 
* Zeitschr. f. Hygiene u. Infekt., xxiii. (1897) p. 490. See Centralbl. Bakt. u. 
Par,, 2 te Abt , iii. (1897) p. 603. 
j Arch. f. Hygiene, 1897, p. 304. See Bot. Centralbl., lxxiii. (1898) p. 216. 
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