88 
On Methods of 
[Monthly Microscopical 
Journal, Aug. 1, 1869. 
that which observation in the fresh state yields with a power 
magnifying 1000 to 1500 times. Those contours which can be 
recognized even during the hfe of the tissues show beside their 
sharpness a pecuhar softness, which makes observation agreeable. 
The natural cavities and fissures are exceedingly well marked from 
their surrounding parts in consequence of the different refracting 
power of their contents. Lastly, contours are visible during life, 
which disappear with the death of the tissues. Though by special 
reagents these can again be made visible, they acquire their full 
value only by our knowing that they have been visible even with- 
out reagents. 
According to what has been said of the present state of instru- 
ments, it may be expedient to conduct comprehensive topographical 
studies with weaker lenses, the study of tissues in preparations 
modified by treatment with medium lenses, and to employ strong 
magnifying power in such cases only for controlling the defth- 
distances (?), and lastly to carry on the investigation of fresh tissue 
exclusively with the best existing instruments.* 
The simplest, but at the same time the most successful and 
most elegant, way of examining under a compound microscope is by 
laying the object upon the middle of the highly polished glass 
slide, covering it with a thin quadrangular plate of glass, likewise 
perfectly clean. The glass plate, also called the glass cover, ought 
to lie with its surfaces parallel to the glass slide, which can only 
be efiected when the stratum to be examined spreads out regularly 
to a greater extent than it. Irregularly bordered thick lumps 
interfere with the examination by forcing the glass cover into an 
oblique position. If the tissue to be examined is distributed through 
a fluid, a small drop of it should be placed upon the glass slide ; the 
top of the drop is then to be gently touched with the glass cover, 
and this then allowed to descend slowly upon it. The inclusion of 
air-bubbles is thus avoided. If the investigation is to be carried on 
for a longer time, or if we are anxious that the medium in which 
the tissues lie shall not become more concentrated at the margins, 
then it is better to apply with a brush a layer of oil round the 
margins of the glass cover ; the preparation will, in this way, be 
protected from evaporation. If after the application of the glass 
cover, a part of the fluid to be investigated should flow beyond its 
margins (the glass cover acquiring thereby an unsteady and easily 
movable position), then its margins must first be dried with filter- 
paper, after which the layer of oil may be put on. In this way we 
obtain the simplest moist chamber. 
* To the binocular stereoscopic microscopes, I cannot attach much value for 
the service they have rendered hitherto. Up to the present they have been used 
with low magnifying powers only. But with the simple microscope the appearance 
of relief may be obtained exceedingly well if, during the observation, the head is 
maintained in a slightly oscillating motion. 
