128 
culiar form, are very interesting; because, in the white 
ones, the striations of the outer lamina, which form 
the corrugations seen in sections of the scales (fig. 
5, d), are longitudinal, while the lower lamina, or 
lamina toward the insect, although smooth, shows 
transverse bands (fig. 5, b, c). In the fact of their 
corrugated surfaces being turned away from the in- 
sect, the scales of Alaus and of some other Coleoptera 
agree with the scales of Lepidoptera and Diptera. 
The 2-7 pointed scales of Ptinus (fig. 6), which are 
nestled amongst its hairs, resemble in a general way 
the plumules of some Lepidoptera. Most of the col- 
oration of the well-known locust-borer, Clytus robi- 
niae, is due to scales (fig. 7), which are of a form not 
rare in the longicorn Coleoptera. 
The Rhynchophora or Curculionidae are the bee- 
tles on which scales most generally occur, and where 
they present their most brilliant coloration. The dia- 
mond beetle of South America, Entimus imperialis, 
often sold by jewellers on account of its brilliancy, 
has scales (fig. 8) and hairs which present to trans- 
mitted light various colors— usually red, blue, and 
yellow; often all three colors with gradations between 
them —on a single scale. By reflected light, or upon 
a black surface like that of the beetle itself, the pre- 
vailing colors are green and purple. The colors which 
are indicated by the direction of the lines on the fig- 
ure (fig. 8 a, c) are those seen by transmitted light. 
When highly magnified, these scales, besides other 
structural characters, show a very fine striation (fig. 
8, d, e), sometimes in one direction on one part of 
the scale, and in another direction on another part. 
This fine striation is probably the cause of the bril- 
liant coloration of these scales. 
All the brilliant coloration of scales of Coleoptera 
appears to be due to interference of light, either by 
fine striation, or by superposed delicate lamellae; as 
can be proved by wetting the scales with chloroform, 
when the color disappears, only to reappear as soon as 
the chloroform is evaporated. Most of the scales of 
Coleoptera contain air; and this air, together with 
the background formed by the coloration of the in- 
sect itself, gives rise to the various changeable hues 
seen in most of the Coleoptera which have scales. 
MICROBES. 
None of the organic substances which form an 
essential part of our sustenance, and are useful in a 
thousand ways, can be kept for more than a few 
days: fermenting and spoiling, they are the despair 
of the economists. In this decomposition the sub- 
stance becomes filled with an immense number of 
very minute organisms. How can a liquid, like milk 
or soup, free from all foreign germs, become invaded 
in a few hours by these innumerable legions of mi- 
crobes? The first hypothesis suggested is, that all 
these organisms are the result of the decomposition, 
and that they are produced spontaneously at the ex- 
pense of the altered substance. ‘This is the theory 
1 By Dr. H. Fou of Geneva. 
Crenéve. 
Translated from the Journal de 
SCIENCE. 
[Vou. IfI., No. 52. — 
of spontaneous generation, so vigorously maintained 
by Pouchet ; and it is certainly one of the greatest 
of Mr. Pasteur’s good offices, that he has refuted one 
by one the arguments of the supporters of this attrac- 
tive theory, pursued them to their last defence with 
his invincible logic and his unexceptionable experi- 
ments. 
The fermentation is produced by the microbes; and 
these, by a wonderfully rapid propagation, are derived 
from germs carried by the air, or adhering to the 
vessels which hold the fermentable liquids. The dili- 
gent researches of Mr. Miquel show that the com- 
paratively pure air of the suburbs of Paris holds 
from a hundred and fifty to a thousand living germs 
per cubic metre. In a hospital at the centre of 
the capital, each cubic metre of air contains from 
five thousand to thirty thousand, according to the 
season. Although these figures appear prodigious, 
they are nevertheless very small, compared to the 
number of spores which cling to all the solid objects 
surrounding us. A simple cleansing is powerless 
to remove them: only fire or strong antiseptic solu- 
tions can destroy them. A fermentable liquid can 
be preserved indefinitely if it is protected from all 
Microbes; but it is easily seen, after what we have 
just said, how difficult it must be to obtain this per- 
fectly insulated state. All these lower vegetable types 
are found in two forms, — 1°, the vegetative or active 
form; and, 2°, the passive form, that is, the spores, 
which play here a part analogous to that of seeds in 
plants. 
In the active state most microbes show little en- 
durance; many species cannot stand a drying of any 
duration; and in moisture a temperature of 70° to 
80° C., continued for two or three hours, destroys 
them almost without exception. Spores are more 
hardy: boiling water does not kill them; but, for this 
purpose, water must be heated to 120°, 130°, and even 
150°. When dry, the spores do not succumb to a 
temperature below 180° to 200°; and, according to 
Mr. Fricz, cold of 110° has no effect upon them. To 
disinfect clothing without burning; would, then, be 
an impossibility, if, fortunately, Mr. Koch had not 
discovered that the germs cannot resist the action 
of a continued current of steam at a temperature of 
100°. 
It is peculiarly difficult to protect a liquid from all 
germs, or to destroy all those which have penetrated 
it; however, it is possible, and the liquid is then said 
to be barren. Certain soups are prepared in this 
way that they may be sown with very small particles 
of substances containing the microbes to be studied; 
and thus the desired species obtained, to the exclu- 
sion of every other. Laboratories devoted to these 
studies annually distribute hundreds and thousands 
of litres of these soups. 
The organisms which here claim our attention be- 
long to three families, all allied to fungi, — moulds, 
yeasts, and microbes proper. Each kind of fermen- 
tation is produced by a certain species of these small 
organisms, and takes place only if the species in 
question is present in the liquid, from the beginning 
of the fermentation, in sufficient numbers not to be 
