REVIEWS. 
173 
of fact lies on the side of the iconoclasts. If this he so, says the reader, 
then M. Pouchet must have this position : — 1. He must show that there 
are no facts in support of the current opinion; 2. He must prove the 
absence of those myriads of germs ; and 3. He must show that the air being 
so acted on as to destroy any germs it might contain, it yet allows of the for- 
mation of organisms. And this is so. There are unquestionably no facts beyond 
the great fact— the terribly serious fact in the struggle of doctrines— of tradi- 
tional belief, in favour of the doctrine of innumerable germs — at least none 
that we know of. As to the other two points, we opine, from a careful study of 
this volume of M. Pennetier’s, that they are very nearly conclusively de- 
monstrated. To lay before our readers the evidence therein adduced would be 
to anticipate the author. We shall therefore merely refer to one or two pas- 
sages in chapter v., in which it is shown that the atmospheric germs do not 
exhibit themselves to the extent that the Panspermists lead us to believe. 
That air had been examined only as to its chemical and physical quali- 
ties, till MM. Moscati, Eobiquet, Baudriniont, and Pouchet thought of sub- 
mitting it to microscopic examination. M. Pouchet, among other contrivances, 
used for this purpose an instrument devised by him, and which he termed 
an Aeroscope. In this the air was projected against discs of glass, which 
thus collected the corpuscles it might contain. When the powder or dust 
thus collected was examined, it was found to be composed of products of food 
and manufactures — such, for example, as starch, grains of silica, filaments of 
wool and cotton, bits of clay, soot, and the debris of plants and insects ; a very 
few spores and infusoria were occasionally found. If, instead of experimenting 
on the air of populous towns, the air was collected from mountains, or on the 
surface of the ocean, the nature of the collected corpuscles was found of course 
to vary in accordance with the locality. MM. Pouchet, Joly, and Musset, 
who thus examined air in every position and locality, have drawn especial 
attention to the rarity, and most frequently the absence of either the ova of 
infusoria or the spores of cryptogams. These savants conceived the ingenious 
idea of making a microscopic examination of snow (which of course in 
its fall would enclose the germs), and they found exactly the same results as 
those stated. M. Pouchet even went so far as to examine the dust deposited 
from the air enclosed in the cavities of the bones of birds, and found its 
composition in exact accordance with the locality inhabited by them. The 
fowl reared in our towns, and the wild falcon showed in this respect very 
remarkable differences. On their part, Burdach, Von Bar, Heusche, Ehren- 
berg, E. Wagner, Leuckart, and more recently Wyman, Bechi, Schaaf- 
hausen, and Baudrimont, have also equally clearly proved the normal absence 
of ova and spores in air. I hasten to say,” adds this latter observer, ^^that 
up to this I have never met in the air we breathe those fantastic beings, 
those monsters with whom human imagination has peopled it.” 
M. Pennetier then takes up the pseudo-positive observation made by 
Lemaire and others, and shows that in no case in which the air was examined 
immediately after being collected were organisms found, and that no test 
was employed to show whether the so-called spores were silica or not, and 
it happens that the siliceous particles are remarkably like in form the spores 
of certain cryptogams. We have said sufficient to show the importance and 
interest of this volume, and we now conclude our observations by giving it a 
hearty commendation to our readers. ' 
