William Benjamin Carpenter.

The microscope and its revelations (Volume 1) online

. (page 16 of 51)
Online LibraryWilliam Benjamin CarpenterThe microscope and its revelations (Volume 1) → online text (page 16 of 51)
Font size
QR-code for this ebook


other extremity of the stem often bears a small brass box filled with cork,
and perforated with holes in its side; this affords a secure hold to
commmon pins, to the heads of which small objects can be attached by
gum, or to which disks of card, etc., may be attached, whereon objects
are mounted for being viewed with the Lieberkuhn ( 115). This



1 " Journ. of Roy. Microsc. Soc.," Vol. iii., pp. 526, 754.



ACCESSORY APPARATUS. 121

method of mounting was formerly much in vogue, but has been less
employed of late, since the Lieberkiihn has fallen into comparative dis-
use. The Stage Vice, as made by Mr. Ross for Mr. Slack, was contrived
for the purpose of holding small hard bodies, such as Minerals, apt to be
jerked out by the angular motion of the blades of the forceps, or very
delicate substances that will not bear rough compression. In this appa-
ratus the blades meet horizontally, and their movements can be regulated
to a nicety with a fine screw. The Stage Vice fits into a plate, as is the
case with Beck's disk-holder, Fig. 94.

119. For the examination of objects which cannot be conveniently
held in the stage-forceps, but which can be temporarily or permanently
attached to disks, no means is comparable to the Disk-holder of Mr. R.
Beck (Fig. 94) in regard to the facility it affords for presenting them in
every variety of position. The object being attached by gum (having a
.small quantity of glycerine mixed with it) or by gold-size, to the surface
of a small blackened metallic Disk, this is fitted by a short stem project-
ing from its under surface into a cylindrical holder; and the holder carry-
ing the disk can be made to rotate around a vertical axis by turning the
milled-head on the right, which acts on it by means of a small chain that
works through the horizontal tubular stem; whilst it can be made to in-
cline to one side or to the other, until its plane becomes vertical, by turn-
ing the whole movement on the
horizontal axis of its cylindrical
socket. 1 The supporting plate be-
ing perforated by a large aperture,
the object may be illuminated by
the Lieberkuhn if desired. The
disks are inserted into the holder,
or are removed from it, by a pair
of Forceps constructed for the
purpose; and they may be safely Beck's Disk-holder,

put away, by inserting their stems

into a plate perforated with holes. Several such plates, with inter-
vening guards to prevent them from coming into too close apposition,
may be packed into a small box. To the value of this little piece of
apparatus the Author can bear the strongest testimony from his own
experience, having found his study of the Foraminifera greatly facili-
tated by it. A less costly substitute, however, which answers sufficiently
well for general purposes, is found in the Object-holder of Mr. Morris
(Fig. 95), which consists of a supporting plate that carries a ball-and-
socket joint in its centre, into the ball of which can be fitted by a taper-
ing stem either a holder for small cardboard disks, or a larger holder
suitable for carrying an ordinary slide. By the free play of the ball-
and-socket joint in different directions, the object may either be made to
rotate, or may be so tilted as to be viewed obliquely or almost laterally.
This instrument can, of course, be used only by side illumination; and
in order to turn it to the best account, the objects to be viewed by it must
be mounted on special disks; but it has an advantage over the preceding,
in being applicable also to objects mounted in ordinary slides. Ine
same purpose is answered, in the Ross Zentmayer Microscopes (59,
72), and in the Improved Beck Microscope ( 65), by turning the stage
round its horizontal axis, so that an object mounted on a slide may b

1 A small pair of Forceps adapted to take up minute objects may be fitted into
the cylindrical holder, in place of a disk.




122



THE MICROSCOPE AND ITS REVELATIONS.



viewed at any desired angle or inclination, when it has been brought into
the most suitable azimuth by the rotating of the stage round its vertical
axis.

120. Glass Stage- plate. Every microscope should be furnished with a
piece of Plate-glass, about 4 in. by 1-^- in., to one margin of which a nar-
row strip of glass is cemented, so as to form a ledge. This is extremely
useful, both for laying objects upon (the ledge preventing them to-
gether with their covers, if used from sliding down when the Miscro-
scope is inclined), and for preserving the stage from injury by the spill-

FIG: 95.




Morris's Object-holder.

ing of sea-water or otner saline or corrosive liquids, when such are in
use. Such a plate not only serves for the examination of transparent,
but also of opaque objects; for if the Condensing-lens be so adjusted as
to throw a side-light upon an object laid upon it, either the Diaphragm-
plate or a slip of black-paper will afford a dark back-ground; whilst ob-
jects mounted on the small black disks suitable to the Lieberkiihn may
conveniently rest on it, instead of being held in the Stage-forceps.

121. Growing Slide. A number of contrivances have been devised of
late years, for the purpose of watching the life-histories of minute aquatic
organisms, and of i cultivating ' such as develop and multiply themselves
in particular fluids. One of the simplest and most effective, that of Mr.
Botterill, represented in Fig. 96, consists of a slip of ebonite, three
inches by one, with a central a,perture of 3-4ths of an inch at its under
side; this aperture is reduced by a projecting shoulder, whereon is ce-




BotteriU's Growing-Slide.



mented a disk of thin glass, which thus forms the bottom of a cell hol-
lowed in the thickness of the ebonite slide. On each side of this central
cell, a small lateral .cell communicating with it and about l-4th inch in
diameter, is drilled-out to the same depth; this serves for the reception
of a supply of water or other fluid, which is imparted, as required, to the



ACCESSORY APPARATUS.



123



central ' growing ' cell, which is completed by placing a thin-glass cover
over the objects introduced into it, with the interposition of a ring of
thin paper, or (if a greater thickness be required) of a ring of cardboard
or vulcanite. If the fluid be introduced jp.^ ^

into one of the lateral cells, and be drawn-
off from the others either by the use,
from time to time, of the small glass
syringe to be hereafter described (127),
or by threads so arranged as to produce
a continuous drip into one and from the
other a constantly renewed supply is
furnished to the central cell, which it
enters on one side, and leaves on the x x

other, by capillary attraction. l Dr. Mad- Maddox's Growing-slide.

dox's Growing -Slide will be understood from the annexed sketch. The
shaded parts are pieces of tinfoil fastened with shellac glue to a glass
slide. The minute fungi or spores to be grown are placed on a glass
cover large enough to cover the tinfoil, with a droplet of the fluid re-
quired. This, after examination to see that no extraneous matter is
introduced, is placed over the tinfoil, and the edges fastened with wax
softened with oil, leaving free the spaces x x for entrance of air. Grow-
ing-slides of this description could be made cheaply with thin glass
instead of tinfoil. 2 For an account of a more elaborate apparatus devised
by Messrs. Dallinger and Drysdale for the prosecution of their admirable
researches hereafter to be noticed (Chap. XL), the reader is referred to
the description and figures given by them in the "Monthly Microscopi-
cal Journal," Vol. xi., 3874, p. 97.

122. Aquatic Box. The Live-Box or Animalcule-cage (Fig. 98, A)
consists of a short piece of wide brass tube, fixed perpendicular into an
aperture of its own diameter in a flat-plate of brass, and closed-in at its
top by the object- tablet, a disk of glass with bevelled edges (B); over
this box there slides a cover, consisting of another piece of brass tube hav-
ing a disk of thin glass fixed into its top. The cover being taken of, a
drop of the liquid to be examined, or any thin object which can be
most advantageously looked-at in fluid, is placed upon the lower plate;
the cover is then slipped over it, and is pressed down until the drop of
liquid be spread out, or the object be flattened, to the degree most
convenient for observation. If the glass disk which forms the lid be ce-
mented or burnished into the brass ring which carries it, a small hole
should be left for the escape of air or superfluous fluid; and this may be-



1 For descriptions of other forms of Growing-Slide, see "Transact, of Microsc.
Society,'' Vol. xiv., N.S., p. 34, and " Quart. Journal of Microsc. Science," N.S.,
Vol. vii.,p. 11.

2 See his paper on Cultivation of Microscopic Fungi, in " Monthly Microscopi-
cal Journ.," Vol. iii. (1870), p. 14. Dr. Maddox recommends the following fluid as
sufficiently hygrometric to keep the spores moist, and as adapted to Fungoid
growths:

Dextrine 2 grains.

Phosphate of Soda and Ammonia 2 "

Saturated Solution of Acetate Potash 12 drops.

Grape Sugar 16 grains.

Freshly distilled water 1 oz.

The water is to be boiled in a large test-tube or beaker for 15 minutes, and
covered whilst boiling and cooling; when settled, it should be poured into per-
fectly clean 2-drachm stoppered bottles, and kept for use.



124



THE MICROSCOPE AND ITS REVELATIONS.




closed up with a morsel of wax, if it be desired to prevent the included
fluid from evaporating. But as it is desirable that the cover-glass should
be thin enough to allow a l-4th or a l-6th inch Objective to be em-
ployed, and as such thin glass is extremely apt to be broken, it is a much
better plan to furnish the brass cover with a screw-cap, which holds the glass
disk with sufficient firmness, but permits it to be readily replaced. It is

always desirable, if possible, to pre-
s ' IGi D & vent the liquid from spreading to the

edge of the disk, since any objects it
may contain are very apt in such a case
to be lost under the opaque ring of the
cover: this is to be avoided by limit-
ing the quantity of liquid introduced,
by laying it upon the centre of the
lower plate, and by pressing dovn
the cover with great caution, so as to
flatten the drop equally on all side ,
stopping short when it is spreading
too close to the margin. If the Live-
box be well constructed, and the glass
disks be quite flat, they will come in-
to such close contact, that objects of
extreme thinness may be compressed
between them; and it may thus be
made, with a little practice, to serve
the purpose of a Compressor ( 125).
In its ordinary form, however, the elevation of the object- tablet above
the stage prevents the Live-box from being used with the Achromatic
Oon denser or Paraboloid: but another form is made by Mr. Swift, in
which the object-tablet is fixed at the bottom of the tube, flush with the
surface of the plate (as shown at c); and as the covering disk is fixed to
the bottom of the cover-tube, and thus slides inside the box-tube, the ob-
ject can be illuminated by any of the means applicable to objects con-
tained in ordinary flat cells ( 123). The only disadvantage of this con-
struction is that the cover-disk must be fixed in the tube which carries it.
123. Infusoria, minute Algae, etc., however, can be well seen by plac-
ing a drop of the water containing them on an ordinary slide, and laying a
thin piece of covering-glass on the top. And objects of somewhat greater
thickness can be examined by placing a loop or ring of fine cotton-thread
upon an ordinary slide, to keep the covering-glass a small distance from
it; and the object to be examined being placed on the slide with a drop
of water, the covering-glass is gently pressed down till it touches the
ring. Still thicker objects may be viewed in the various forms of t cells '
hereafter to be described ( 171-3); and as, when the cells are filled
with fluid, their glass covers will adhere by capillary attraction, provided
the superfluous moisture that surrounds their edges be removed by blot-
ting-paper, they will remain in place when the Microscope is inclined.
An Annular Cell, that may be used either as a f live-box' or as a ' grow-
ing-slide,' has lately been devised by Mr. Weber (U. S.). It is a slip of
plate-glass of the usual size and ordinary thickness, out of which a cir-
-"i 'cell' of 3-4ths inch diameter is ground, in such a manner that



Aquatic Box or Animalcule-Cage, as seen in
perspective at A, and in section at B and c.



cular



its bottom is convex instead of concave, its shallowest part being in the
centre, and the deepest round the margin. A small drop of the fluid
to be examined being placed upon the central convexity (the highest



ACCESSORY APPARATUS. 125

part of which should be almost flush with the general surface of the
plate), and the thin glass-cover being placed upon is, the drop spreads
itself out in a thin film, without finding its way into the deep furrow
around it; and thus it holds-on the covering-glass by capillary attraction,
while the furrow serves as an air-chamber. If the cover be cemented
down by a ring of gold-size or dammar, so that the evaporation of the
fluid is prevented, either Animal or Vegetable life may thus be main-
tained for some days, or, if the two should be balanced (as in an Aqua-
rium), for some weeks. 1 An improvement has been devised by Dr. Ed-
monds in the form of this Annular Cell; which he also makes to serve
as a ' gas-chamber ' for the introduction of gases or vapors into the Annu-
lar space. The central prominence is shaped as a truncated paraboloid;:
and while, by focussing in the object a 2-inch objective used as a conden-
ser, a bright field is obtained, this may be exchanged for a dark field by
putting the condenser out of focus (so that its light is thrown on the
sides of the paraboloid), and by gumming a black disk on the centre of
its under surface. A straight groove being cut in the slide, parallel to
its long side, and tangentially to the annular groove which it should
equal in depth, two fine glass tubes are cemented in it; one of them,
which is left projecting beyond the end of the slide, being connected
with a slender elastic tube through which gases or vapors may be pro-
jected into the annular space, while the other serves to convey them
away. 2

124. Zoophyte Trough. For the examination of larger aquatic Ani-
mals or Plants under low or moderate powers, recourse may be advanta-
geously had either to the original Zoophyte-trough of Mr. Lister (which-
is still kept on sale by most Makers), or to a form lately devised by Mr.
Botterill, which has several

advantages over the older one. Eio. 99..

This consists of two plates of
vulcanite, a back and a front,
shaped as in Fig. 99, connected
together by three brass screws;
these, being fixed in the faack
plates, pass through the front,
where their projecting ends are
furnished with small milled-
heads. Between these plates Botteriirs Zoophyte Trough,

are two rectangular plates of

glass, cut to such a length as to lie between the two side-screws of the
vulcanite plates, and having such a breadth that while their lower
edges rest on the bottom-screw, their upper are flush with the top of the
vulcanite disks. The glass plates are kept apart by a half -ring of vul-
canized india-rubber, of such a diameter as to lie just outside of the semi-
circular margin of the vulcanite plates; and they thus form the sides and
bottom of a trough, which is made water-tight by a moderate pressure
exerted by turning the milled-heads. The space between the two glass
plates may be varied by using half-rings of different thicknesses; whilst,
if it be desired to use a higher power than will work through ordinary
glass, a front plate of thin glass may be substituted. One great advan-
tage of this arrangement is the facility with which the pieces composing

1 " Journ. Roy. Microsc. Society," Vol. ii. (1879), p. 55.

2 Ibid., Vol. iii. (1880), p. 585. This Parabolized Gas-Slide is made by Messrs..
Beck.




126



THE MICROSCOPE AND ITS REVELATIONS.



I'TO.




Schiek's Compressor.



it may be taken apart, either for cleaning or for the repair of a fracture
an accident to which the use of thin #lass of course renders it specially
liable.

125. Compressor. The purpose of this 'nstrument is to apply a
gradual pressure to objects whose structure can only be made out when
they are thinned by extension, while their organization is so delicate as
to be confused or altogether destroyed by the slightest excess of pressure.
For the examination of such, an instrument in which the degree of
compression can be regulated with precision is almost indispensable. The
Compressorium represented in Fig. 100 was originally devised by Schiek
of Berlin; whilst its details were modified by M. de Quatrefages, who

constantly employed it in
his elaborate and most suc-
cessful researches on the or-
ganization of the Marine
Worms. Being, however,
deficient in any provisions
for securing the parallelism
of the approximated sur-
faces, it has been superseded
,jj other forms devised expressly with that view. In Ross's Improved
Compressor, shown in Fig. 101, the upper plate D is attached to
? slide that works between grooves in the vertical piece c, so that,
when raised or lowered by the milled-head, it always maintains its
parallelism to the lower plate A. The thin glass carried by the upper

plate D (which can be turned aside on
a swivel joint, as shown in the lower
figure) is a square that slides into
grooves on its under side, so as to be
easily replaced if broken. The glass
to which it is opposed is a circular
disk lodged in a shallow socket in plate
B, which is received into a part of the
lower plate A that is sunk below the
rest. The plate B carrying the lower
glass can be drawn out (as shown in
the lower figure) and laid upon the
Dissecting Microscope, to be replaced
in the Compressorium after the object
has been prepared for compression.
The only drawback to the use of this
instrument lies in the inconvenience of
using it in the reversed position so as
to look at the object from its under
side. This reversion is provided for in
the two forms of the instrument' made
by Messrs. Beck, which are shown in
Figs. 103, 104. In both, the upper



FIG. 101.




Ross's Improved Compressor,



and the lower glasses are fixed, upon a plan devised by Mr. Slack, by
means of flat-headed screws, two to each glass (Fig. 103, A), the heads
fitting into holes of the opposite frame, so as to permit the close approxi-
mation of the two glass surfaces. In their Parallel Plate Compressor
(Fig. 102) the constant parallelism of the two plates is secured by the two
parallel bars, a, a; while the degree of their approximation and pressure



ACCESSORY APPARATUS.



127



is regulated by the screw I, which works out of centre in a conical hole
of the lower frame, so that, the further it is introduced, the more closely
the two frames, with their glasses, are approximated. This pattern works
equally well whichever side is uppermost. In the Reversible Cell Com-
pressor of the same makers (Figs. 103 B, 104) the upper glass is held down
by a ring a, which screws-on to that which bears the lower one, giving
any degree of pressure that may be required. When screwed together,
they form a cell that fits into the plate #, and is attached to it by the
milled-head c; by unscrewing which the cell can be instantly detached
and replaced in a reverse position. In all these Compressors, it is easy
to vary the thickness qf the glass within convenient limits; and the ob-



Fra. 102,



Era. 105.
ABC




Beck's Parallel Plate Compressorium.



Tic. 103.




Beck's Reversible Cell Compressorium.





Dipping Tubes.



Glass Syringe.



server should be always provided with a stock of glass slips and disks of
the requisite sizes and of different thicknesses, suitable to the kind of
investigation he may be prosecuting. As thin glasses, when used for
compression, are very liable to fracture, the power of immediately re-
placing them without the employment of cement (as in Mr. Slack's con-
struction) is a great convenience.

126. Dipping Titles. In every operation in which small quantities
of liquid, or small objects contained in liquid, have to be dealt with by
the Microscopist, he will find it a very great convenience to be provided
with a set of Tubes of the forms represented in Fig. 105, but of some-



128 THE MICROSCOPE AND ITS REVELATIONS.

what larger dimensions. These were formerly designated as c fishing
tubes;' the purpose for which they were originally devised having been
the fishing-out of Water-fleas, aquatic Insect-larvae, the larger Animal-
cules, or other living objects distinguishable either by the unaided eye or
by the assistance of a magnifying-glass, from the vessels that may contain
them. But they are equally applicable, of course, to the selection of
minute Plants; and they may be turned to many other no less useful pur-
poses, some of which will be specified hereafter. When it is desired to
secure an object which can be seen either with the eye alone or with a
magnifying-glass, one of these tubes is passed down into the liquid, its
upper orifice having been previously closed by the forefinger, until its
lower orifice is immediately above the object; the finger being then re-
moved, the liquid suddenly rises into the tube, probably carrying the
object up with it; and if this is seen to be the case, by putting the finger
again on the top of the tube, its contents remain in it when the tube is-
lifted out, and may be deposited on a slip of glass, or on the lower disk
of the Aquatic-box, or, if too copious for either receptacle, may be dis-
charged into a large glass cell (Fig. 120). In thus fishing in jars for any
but minute objects, it will be generally found convenient to employ the
open-mouthed tube c; those with smaller orifices, B, c, being employed
for 'fishing' for Animalcules, etc., in small bottles or tubes, or for
selecting minute objects from the cell into which the water taken up by
the tube A has been discharged. It will be found very convenient to
have the tops of these last blown into small funnels, which shall be cov-
ered with thin sheet India-rubber; for their action (like that of the stop-
per of the Dropping-bottle, Fig. 138) can then be regulated with the
greatest nicety by the pressure of the finger.

127. Glass Syringe. In dealing with minute Aquatic objects, and in
a great variety of other manipulations, a small Glass Syringe of the pat-
tern represented in Fig. 106, and of about double the dimensions will be
found extremely convenient. When this is firmly held between the
fore and middle fingers, and the thumb is inserted into the ring at the
summit of the piston-rod, such complete command is gained over the
piston, that its motion may be regulated with the- greatest nicety: and
thus minute quantities of fluid may be removed or added, in the various
operations which have to be performed in the preparation and mounting
of Objects (Chap, v.); or any minute object may be selected (by the aid
of the simple Microscope, if necessary) from amongst a number in the
same drop, and transferred to a separate slip. A set of such Syringes,
with points drawn to different degrees of fineness, and bent to different
curvatures, will be found to be among the most useful ' tools 9 that the
working Microscopist can haVe at his command.




Forceps.



128. Forceps. Another instrument so indispensable to the Micro-
scopist as to be commonly considered an appendage to the Microscope, is
the Forceps for taking up minute objects; many forms of this have been
devised, of which one of the most convenient is represented in Fig. 107,



ACCESSORY APPARATUS. 129

of something less than the actual size. As the forceps, in Marine re-
searches, have continually to be plunged into sea- water, it is better that
they should bo made of brass or of German silver than of steel, since the
latter rusts far more readily; and as they are not intended (like Dissecting-
forceps) to take a firm grasp of the object, but merely to hold it, they
may be made very light, and their spring-portion slender. As it is es-
sential, however, to their utility, that their points should meet accurately,
it is well that one of the blades should be furnished with a guide-pin
passing through a hole in the other.

The foregoing constitute, it is believed, all the most important pieces
of Apparatus which can be considered in the light of Accessories to the



Online LibraryWilliam Benjamin CarpenterThe microscope and its revelations (Volume 1) → online text (page 16 of 51)