530 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Experiments on similar lines made with a number of other pathogenic 
micro-organisms on refractory animals gave negative results. 
Denitrifying Aerobic Ferment found in Straw.* — After alluding 
to the existence of the nitrifying ferment present in all cultivated 
soils, M. E. Breal shows that there exists another ferment in straw and 
other vegetable debris which has a denitrifying action. If straw be 
tested with diphenylamin sulphate, the presence of nitrates on its surface 
can always be demonstrated ; but if it be kept for a few days in water 
the reagent no longer indicates nitric acid, although it is sensitive to 
one ten-millionth of a gramme. If to the straw water be added 
continually increasing quantities of nitrates, these will rapidly dis- 
appear. 
That this reduction of nitric acid is due to a ferment may be shown 
by sterilizing the straw by means of heat or an antiseptic such as the 
bichloride of mercury ; the nitrates then no longer disappear. 
Bacterioidal Forms in Tissues and Eggs of Insects. j — Prof. F. 
Blochmann describes bodies which resemble in many respects bacteria. 
In the fat-body of insects, such as Phyllodromia germanica and Periplaneta 
orientalis, these rodlets may be easily seen if a small piece of this tissue 
be squeezed between cover-glass and slide, and examined in water or 
some indifferent menstruum. They may easily be demonstrated as cover- 
glass preparations and by staining with gentian violet. The rodlets are 
6-8 p long, and usually slightly curved. The ends stain deeply, while 
the middle part remains as a clear space. Sections exhibit the structure 
and relations of these bodies even better than cover-glass preparations. 
The material should be fixed with alcohol, and stained with logwood, or by 
Gram’s method. 
The rodlets are seen singly or in pairs, the pairs being shorter than 
the single rods. In some cases there is an expansion at the ends which 
seems constricted off from the rod. Similar appearances were observed in 
some eggs of these insects. 
Besides the two insects mentioned, the rodlets were found in many 
ants wherein they are longer, measuring 10-12 /x, and exhibiting in the 
middle a strongly refracting corpuscle, which became more visible after 
treatment with 1 per cent, acetic acid. 
"With regard to these bodies, the important question arises whether 
we have to deal with bacteria living in symbiosis with the insects, or 
whether the bodies are products of the cells in which they are found. 
In support of the former view is the fact that Prazinowski has culti- 
vated the bacterioidal forms of the Leguminosae, while against it are the 
negative results of the author’s own cultivation experiments. 
Pigment of Bacillus pyocyaneus.f — Dr. Rohrer cultivated, from the 
pus of a case of acute otitis media, Bacillus pyocyaneus on gelatin rolls 
to which 1/4-1 ccm. of 2 per cent, hexaethyl- violet solution had been 
added. The principal result appears to have been that though the 
formation of pigment was not prejudiced, yet the blue and fluorescing 
pigment was replaced by dark brown-red pigment, pyoxanthin. On potato, 
* Comptes Rendus, cxiv. (1892) pp. 681-4. 
f Centralbl. f. Bakteriol. u. Parasitenk., xi. (1892) pp. 234-40. 
j Tom. cit., pp. 327-35. 
