ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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action on bacteria. The chief results obtained were that litmus offered 
greater resistance to bacterial reduction than methylen-blue, and that in 
consequence the latter was more suitable than the former for experimental 
purposes. One of the conclusions arrived at was that, while most bacteria 
possess reducing properties, a reduction might not be perceptible from 
their action on pigments owing to special conditions. 
Many bacteria lose the power of reducing pigments at 37° which 
they possess at 16°. The behaviour of different bacteria to pigments 
may be different, i.e. while some reduce only metliylen-blue, others will 
reduce methylen-blue and litmus, and among the latter are some which 
reduce litmus more energetically and persistently than methylen-blue. 
The explanation of this difference in bacterial behaviour is perhaps to 
be sought in the specifically different metabolic processes of the proto- 
plasm rather than in the reducibility of the pigments. 
The reduction process is regarded as being brought about through 
the agency of the metabolic products, and not by the bacterial proto- 
plasm. 
The intensity of reduction in those bacteria which easily reduce 
methylen-blue is proportional to the degree of the growth -energy of 
those bacteria ; and the rapidity of reduction is regarded as an expression 
of the aerobic or anaerobic growth-peculiarities of the bacteria. It is 
pointed out that the difficult reducibility of litmus might b°, employed 
as a diagnostic criterion between B. typhosus and B. coli , as the former 
never reduces litmus and the latter always does. 
Ocean Bacteria.* — Prof. Fischer and Dr. Bassengo have investigated 
at different times a section of the Atlantic stretching from 60° north 
latitude to 8° south. Near land the number of bacteria was greatest, 
and diminished rapidly seawards. On the edge of an ocean current, and 
especially where a current came up from below, they were more numerous 
again. Bacteria were more numerous below than on the surface ; they 
were found at a depth of 1100 m. (596 fathoms), and between 200 and 
400 m. existed in greater numbers than at the surface. The paucity at 
the surface is attributed to the germicidal action of sunlight. Most of 
the kinds were bacteria ; hyphomycetes were few, and found only near 
land ; blastomycetes occurred abundantly, and at such distances from 
land that it is certain they develope in the sea. The bacteria were of 
all sizes and shapes, and all were endowed with spontaneous movement 
in certain stages of development. None were sporogenic ; some were 
potential anaerobes, some chromogenic, and some luminous. 
Composition and Nature of Tuberculin.f — In a preliminary com- 
munication on the chemical composition of tubercle bacilli and tuberculin, 
Dr. Yignerat remarks that, according to Koch, tubercle bacilli consist of 
three substances, tuberculin and two fatty acids, one of which is soluble 
in alcohol and the other not. It is to the fatty acid insoluble in alcohol 
that the specific staining of the bacilli is due. After detailing the steps 
of his chemical investigations, the author remarks that tuberculin reacts 
with BaCl 2 and Fe 2 Cl 6 like succinic acid salts ; and when treated with 
nitric acid and evaporated, crystals of succinic acid are obtained by 
* Deutsche Med. Wochenschr., Sept. 14, 1899. See Brit. Med. Journ., 1899, ii. 
p. 864. f Centralbl. Bakt. u. Par., l te Abt., xxvi. (1899) pp. 293-4. 
