ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
101 
gummosis known as “ gummose bacillaire ” and the formation of thylleo 
in the living part of the wood. The development of the bacillus is 
greatly facilited by a moist air. 
M. L. Ravaz * describes similar phenomena, but states that the 
formation of gum is not characteristic of the disease, seeing that it may 
take place in the healthy vine.® 
Herr K. Schilbersky f reviews the accounts of this disease of the 
vine given by different observers, and advocates the view that it is not 
an independent disease, but a secondary result of other pathogenic con- 
ditions. 
Morphological and Physiological Variability of Microbes. t — In a 
monograph on the variability exhibited bv microbes, M. A. Rodet first 
discusses the morphological variations. Bacillus anthracis appears in 
the blood in the form of rodlets of equal length. In gelatin cultures these 
may extend to filaments of any length, while spore-formation depends 
on the nutrient medium. The poorer this is in nutritive substances the 
more numerous are the spores. In this connection too, temperature 
exerts considerable influence. With many other bacteria the same 
results are obtained ; for example, B. prodigiosus , Megatherium , septicus , 
cyanogenus, pyogenes , &c. Bac. coli com. exhibits these morphologi- 
cal variations in a high degree. At a temperature of 31° it shows short 
rodlets, at 42°-46° the rodlets are much longer. But even the same 
culture will exhibit quite different appearances, at one time being quite 
coccoid, at another very long. The mobility and the number of flagella 
are also very variable. The morphological variations of the Proteus 
group are very numerous (very long rods to cocci), and in general this 
is the case with every species. 
The physical macroscopical characters of the same species are just 
as little always the same, e. g. Bac. anthracis shows more or less large 
flakes on the medium. Cholera colonies on gelatin are different in 
different cases, and the polymorphism of this vibrio on gelatin is so 
great that no bacteriologist would trust to the appearances on this 
medium alone. Potato cultures of B. coli may be so dissimilar that 
they often resemble a crowd of different species. 
Like the morphological and physical characters, the chemical pro- 
perties are also subject to variation. Thus the pigment of B. pyocyaneus 
depends on the quantity of oxygen. The colour in albumen cultures is 
green, in pepton cultures blue. So, too, the secretion of diastase by 
Bac. mesentericus milgaius is variable, as is the indol reaction of the coli 
and cholera bacteria. The intensity of pigment production of Bac. pro- 
digiosus is not always the same. In alkaline fluids it may even be 
absent. By long cultivation in the laboratory, Staph, aureus gradually 
loses its colour. Streptococcus erysipelatis produces at one time inactive 
lactic acid, at another laevolactic acid. The toxic properties of the same 
species are often very different (diphtheria, B. coli, cholera). 
Moreover, the biological characters, e. g. the resistance of one and 
the same species, are not always alike ; and often it appears that an older 
* Rev. de Viticulture, 1895, 12 pp. and 14 figs. See Bull. Soc. Bot. France, xlii. 
(1895) Rev. Bibl., p. 588. f lu Russian ; see Bot. Centralbl., lxiv. (1895) p. 90. 
I Paris, 1895. See Centralbl. f. Bakteriol. u. Parasitenk., l la Abt., xviii. (1895) 
pp. 49S-5UI. 
