SCIENTIFIC SUMMARY. 
565 
water in constant agitation. The public, the medical profession, and 
sanitarians generally ought to watch the proceedings of any board entrusted 
with such vital interests. 
MICROSCOPY. 
Structure of the Valves of Pleurosigma. — Dr. Wallich calls attention to 
the error into which most observers have fallen, in supposing that the 
diagonal and rectangular series of lines (as the case may be) constitute the 
portions of the valves which, under the high magnifying powers of the 
microscope, become convertible into the so-termed dots, heads, or hexagons 
— the fact being (he says) that the striae seen under the lower powers, if 
properly exhibited, are never convertible into anything but lines, whereas 
the dots, beads, and hexagons are the imperfect expositions of the structure 
occurring in the spaces included between the intersections of those lines. 
Dr. Wallich always prefers oblique light for the examination, and by its 
use he concludes that he has ascertained beyond question that the marking 
on P. angulatum, halticum, &c., is produced by pyramidal sharp faces, and 
finely acuminate elevations on the surface. He is of opinion that the 
intervening spaces in P. angulatum and its allies exhibit elevations, but 
thinks it probable that the corresponding spots on P. hippocampus are occu- 
pied by depressions. Dr. Wallich’s paper in the “ Annals of Natural 
History ” for May, enters very fully into the debated subject, and is worth 
consulting. 
Fermentation produced by Infusoria. — M. Pasteur, in the “ Comptes 
Rendus,” confirms a statement laid before the Academy two years since, 
that there exist infusory animalcules possessing the two properties of living 
without free oxygen, and of acting as ferments. The new example adduced 
is the fermentation of tartrate of lime, determined by the presence of an 
infusory animalcule, existing without free oxygen, and belonging, like that 
which determines the butyric fermentation, to the genus Vihro. He promises 
to demonstrate in a future communication that there are other animalcule 
ferments of putrefaction under exposure to air, which are found associated 
with infusoria, or mucors, that consume the free oxygen, and fulfil the 
double purpose of agents of combustion with reference to the organic 
materia], and of agents of preservation for the infusoria ferments, by pro- 
tecting them from the contact of the ozygen of the air. 
The Formation of Infusoria. — Professor Wyman, of Harvard College, 
has made a series of experiments of a most interesting character, in which 
the results of Pasteur have been in a great measure negatived. Living 
organisms made their appearance in many instances where even greater 
precautions were taken than those mentioned by the French observer. 
In Wyman’s experiments, solutions of organic matter, some of them pre- 
viously filtered, have been boiled at the ordinary pressure of the atmosphere 
for a length of time varying from fifteen minutes to two hours, and 
exposed to air purified by heat. In four instances the contents of the 
flasks were unchanged at the time they were opened ; but in all the rest 
Vibrios, Bacteriums, and other organisms appeared. In nearly every * 
2 q 2 
