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260 | on) Mapes: and Physiol vill pm 
possess a power of movement ot various degrees of aétivity, oat Sys 
in vibrations and a creeping motion backwards and forwards ; but the | 
causes and mechanism of these movements are not yet certainly known 
in any case. As soon as the nitrogenous substances in the substratum 
are entirely consumed, the Bacteria gradually cease multiplying, and | 
pass over from their motile to their stationary condition, usually excret- 
ing at the same time an intercellular substance, and congregating into 
gelatinous colonies (Fig. 391, IV.). In this state, when they are known 
as Zooglea, they still continue to grow, divide, and, under certain cir- 
cumstances, again to become active. Those Bacteria which develope 
in damp air on nitrogenous nutrient substances also form gelatinous 
masses ; they usually produce, as secondary products of their process of 
assimilation, red, violet, yellow, green, and brown colouring substances. 
The Schizomycetes, being all unicellular, are at present included under 
Algze, among which they show the nearest affinity to the Nostocacez. 
They were at one time placed among Fungi, to which they show an 
analogy in their mode of life, since they live on organic substances, 
obtaining their nutriment from them ; all fluids, in fact, which con- 
tain organic substances undergoing decomposition, have particular forms | 
of the Schizomycetes, and usually in large numbers. It is, neverthe- 
less, still an open question whether these organisms belong to the 
animal or vegetable kingdom, or whether they occupy an intermediate 
position between the two, partaking of the characters of both, or may 
be erected into an independent kingdom, the Protista [of Haeckel], ie 
point of departure of the two others. 
When water which contains living Bacteria is evaporated, a great 
number of these organisms are carried into the air, and in particular the 
most minute globular forms, the J/ecrobacteria. The germs of Bac- 
teria which, in consequence, rise into the air whenever putrefying fluids 
are evaporated, are carried down everywhere by rain, are sucked in 
with the air in breathing, and hence become causes of putrefaction in 
all nitrogenous substances exposed to the air, since their vitality is not 
lost in the atmosphere. Of this nature are many and possibly all causes 
of putrefaction and the propagators of contagious diseases. These Jatter 
are mostly immotile globular Bacteria (Sperobacteria), often united 
together into clusters, drinking-water being usually considered the 
medium of their propagation. ‘The blood of animals attacked by con- 
tagious diseases generally contains, a considerable time before their 
death, a prodigious number of Bacteria—straight, rigid, cylindricalrods 
which are bent at an obtuse angle in one or two places, extremely 
slender, and usually not more than from ‘004 to ‘o12mm. in Jength. 
In the intestines, excrements, and vomit of cholera-patients are found, 
