98 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
trace of nitrogen. The cultivations were made in flat-bottomed vessels 
covered over with bell-jars. The external air reached the cultivations 
only after it had passed through washing-bottles filled with potash and 
sulphuric acid. The cultivations were distinguished by specific cha- 
racters, — the development of gas and the formation of acid, and the 
presence of zoogloea masses. The acid was chiefly butyric, and the 
zoogloea masses were formed of and by a large bacillus often containing 
spores. There were other organisms, but their development was poor, 
sometimes abnormal ; they did not produce either gas or butyric acid. 
The morphological characters of the bacillus which possesses the 
property of assimilating free nitrogen are somewhat striking. The 
young cells are rodlets 1 • 2 fx broad and from twice to four times as long. 
They are motionless, and stain deeply with anilin pigments. Spore- 
formation is preceded by a general swelling of the cell, which becomes 
ellipsoidal in shape, and at this period iodine stains the organism black, 
leaving the two poles uncoloured. Ripening of the spore is indicated 
by the conversion of the mother-cell into a sort of sac, open or expanded 
at one end. 
Bacillus mycoides and Nitrification.* — According to M. E. Marchal 
the gradual oxidation that takes place in the soil when the nitrogen of 
organic matter is converted into nitrates (nitrification) is accomplished 
in three stages : — transformation of organic nitrogen into ammonia ; 
formation of nitrous acid from ammonia ; conversion of the nitrites thus 
formed into nitrates. The first stage is effected by microbic agency, 
bacteria yeasts and moulds which swarm in the upper layers of the earth. 
Amongst these, Bacillus mycoides (the earth bacillus) possesses not 
only the widest distribution but the most energetic action ; and under 
its influence oxygen is carried to the elements of albumen, carbon is 
changed to carbonic acid, sulphur into sulphuric acid, hydrogen partly 
into water, leaving ammonia as the residue of the oxidation. Small 
quantities of peptone, leuciu, tyrosin, and fatty acids are also produced. 
The optimum conditions for this ammonia-making microbe are : a 
temperature about 30° ; perfect aeration ; slight alkalinity of the medium ; 
the albuminous solutions must be thin. Besides egg-albumen, the other 
forms of albumen, and also creatine, leucin, tyrosin, and asparagin are 
affected in the same way, while urea and nitrate of urea are unaffected. 
Bacillus mycoides, though a former of ammonia and an aerobe in presence 
of azotized organic matter, has a denitrifying action, and becomes 
anaerobic when associated with easily reducible bodies (nitrates) ; and 
in the absence of free oxygen in solutions containing organic matter 
(sugar albumen) reduces nitrates to nitrites and ammonia. Hence it 
has the power of setting free ammonia by two quite opposite processes : 
by oxidation in one case, by reduction in the other. 
Bactericidal Power of the Blood. f — Prof. J. Denys and M. A. Kaisin 
made a series of experiments to test the value of some objections recently 
raised to the bactericidal projjerty of the blood. These objections were : — 
(1) The destruction of microbes is due to sudden change of medium. 
(2) The destruction is proportional to the number of microbes, and 
this shows that the cause is not to be sought in the blood but in the 
* Bull. R. Acad. Sei. Belg., xxv. (1893) pp. 727-71 (2 figs.). 
t La Cellule, ix. (1893) pp. 337-93. Cf. this Journal, 1893, p. 517. 
