D257P
 1863
id^ui'J.-iL'iJ-'L^-i. 
 
 
 
THE
PREPARATION AND MOUNTING
MICROSCOPIC OBJECTS
       BY

THOMAS DAVIE'S.
■Vrk°i
s
     NEW YORK:
WILLIAM  WOOD & CO.,
    61 Walker Street. 
Q'H
        R. CRAIGHEAD,
Printer, Slereoiyper, and Electrotyper,
      daiton  3SuiIt>ii»s»
    81, 83, and 85 Cenl« Stree/. 
CONTENTS.
                          CHAPTER I.
Apparatus..............................
                         CHAPTER II.
To prepare and mount Objects " Dry ".............................  21

                         CHAPTER III.
Mounting in Canada Balsam.....................................  57

                         CHAPTER IV.
Preservative Liquids, etc., particularly where Cells'are used..........  81

                         CHAPTER V.
Sections and how to cut them, with some Remarks on Dissection.......  92

                         CHAPTER VI.
Injection..................................................... 115

                         CHAPTER VII.
Miscellaneous................................................. 131 
si
 1 
PREFACE.
In bringing this Handbook before the public, the Author
believes that he is  supplying a want which has been long
felt.   Much information concerning the  " Preparation and
Mounting of Microscopic Objects " has been already pub-
lished ;  but mostly as supplementary  chapters only,  in
books written professedly  upon the  Microscope.   From
this it is evident that it was necessary to consult a number
of works  in  order to obtain  anything like a  complete
knowledge of  the subject.   These pages, however, will be
found  to  comprise  all the  most  approved methods  of
mounting, together  with the results of the  Author's expe-
rience, and that of  many of his friends, in  every depart-
ment of microscopic manipulation;  and as it is intended
to assist  the beginner as well  as  the advanced  student,
the very rudiments  of the art have not been  omitted.
  As there is a diversity of opinion as  to the best mode
of proceeding in certain cases,  numerous  quotations have 
Vlll                    PREFACE.
been  made.  Wherever this  has been done, the Author
believes that he has acknowledged the source from which
he has taken the information;  and he here tenders his sin-
cere thanks to those friends who so freely allowed him to
make use of their works.   Should, however, any one find
his own  process in these pages unacknowledged, the author
can only plead  oversight, and his regret  that such should
have been the case. 
THE
     PREPARATION AND MOUNTING
                     OF

MICROSCOPIC   OBJECTS.
                     CHAPTER  I.

                         APPARATUS.

Before entering into the subject of the setting of Objects for the
Microscope, the student must be  convinced of the necessity of
cleanliness  in everything relating to the use of that instrument.
In no branch is this  more  apparent than in  the preparation of
objects; because a  slide which  would be considered perfectly
clean when viewed in the ordinary way is seen to be far otherwise
when magnified some hundreds of diameters :  and those constant
enemies, the floating  particles of  dust, are everywhere present,
and it is only by unpleasant experience that we fully learn what
cleanliness is.
  Any object which is to be viewed under the  microscope must,
of course, be supported in some way—this is now usually done by
placing  it upon a glass  slide, which on account  of the transpa-
rency  has  a great advantage over  other  substances.   These
" slides" are almost always made  of one size, viz., three inches
long by one broad, generally having the edges ground so as  to
remove all danger of scratching or cutting any object with which
they may come in contact.   The  glass  must  be very good, else
the surface will  always present the appearance of  uncleanliness
and dust.   This dusty look is very common amongst the cheaper
                             2 
10
PREPARATION AND MOUNTING
kinds of slides, because  they are usually " sheet" glass;  but is
seldom found in those of the quality known amongst dealers by
the name of " patent  plate."  This latter is more  expensive at
first, but in the end there is little difference in the cost, as so many
of the  cheaper slides cannot be used for delicate work  if the
mounted object is  to be seen  in perfection.   These slides vary
considerably  in thickness;  care should,  therefore,  be taken  to
sort them, so that the more delicate objects with which the higher
powers are to be used may be mounted upon the thinnest,  as the
light  employed in  the illumination is then less interfered with.
To aid the microscopist in this work, a metal circle may be pro-
cured, having a number of different sized openings on the outer
edge, by which the glass slides can be measured.  These openings
are numbered, and the slides  may be separated according to these
numbers; so that when mounting any object there will be no need
of a long search for that glass which is best suited to it.
   When fresh from the dealer's hands, these  slides are generally
covered with dust, &c, which may be removed  by well washing
in clean rain-water ; but if the impurity is obstinate,  a little wash-
ing soda may  be added, care being taken, however, that every
trace  of this is removed by subsequent waters, otherwise the crys-
tals will afterwards form upon the surface.  A clean linen cloth
should be used to dry the slides, after which they may be laid by
for use.   Immediately, however, before being used for the  recep-
tion of objects by any of the  following processes, all  dust must be
removed by rubbing the surface with clean  wash-leather or a
piece of cambric, and, if needful, breathing upon  it, and then
using the leather or cambric until perfectly dry.  Any small par-
ticles left upon the surface may generally be removed by blowing
gently upon it, taking care to allow no damp  to remain.
   We have  before said, that  any object to  be viewed  in  the
microscope must have its support; but if this object is to be pre-
served, care must be taken that  it is  defended from  the dust and
other impurities.   For this purpose it is necessary to use  some
transparent cover, the most usual at one time being a plate of mica,
on account of its thinness; this substance is now, however never
used, thin  glass being  substituted,  which  answers admirably.
Sometimes it is required to  " take up " as little space as possible, 
OF MICROSCOPIC OBJECTS.
11
owing to the shortness of focus of the object-glasses.  It can be
procured of any thickness, from one-fiftieth to one-two-hundred-
and-fiftieth of an inch.  On account of its want of strength it is
difficult to cut, as it is very liable to "fly " from the point of the
diamond.   To  overcome this tendency as much as possible, it
must be laid upon a thicker piece,  previously made  wet with
water, which causes the thin glass to adhere more firmly, and con-
sequently to bear the pressure required in  cutting the covers.
The process of cutting being so difficult, especially with the thin-
ner kinds, little or nothing is gained by cutting those which can
be got from the dealers,  as the loss and breakage is necessarily
greater in the hands  of  an amateur.  It is convenient, however,
to have  on hand a  few larger pieces, from which unusual sizes
may be cut when required.
  If the pieces required are rectangular, no other apparatus will
be  required save  a  diamond and a  flat  rule ;  but if  circles are
wanted, a machine  for that purpose should be used (of which no
description  is  necessary here).  There  are, however, other  con-
trivances which answer tolerably well.  One method is, to cut out
from  a  thick piece  of  cardboard a circle rather larger than the
size  wanted.   Dr. Carpenter  recommends  metal rings with  a
piece of wire  soldered on either side ; and this, perhaps, is the
best,  as  cardboard is apt to become rough  at the edge  when
much used.  A friend of mine uses thin brass plates with circles
of various sizes " turned " through them, and a small raised han-
dle placed at one end.   The diamond must be passed round the
inner edge, and so managed as to  meet again in the same line,
in order that  the  circle may be  true, after which  they may be
readily  disengaged.  The  sizes usually kept  in stock by the
dealers are one-half, five-eighths, and three-quarters inch diameter ;
but other sizes  may be had to order.
  For the information of the beginner it may be mentioned here
that the  price  of the circles is a little more than of the squares;
but this is  modified in  some  degree by the  circle being rather
lighter.   If appearance,  however,  is  cared for at all, the circles
look much  neater  upon the slides when  not covered  with the
ornamental  papers ;  but if these  last  are used (as will shortly be
described) the  squares are equally  serviceable. 
12
PREPARATION AND MOUNTING
  As before mentioned, the thin glass is made of various thick-
nesses, and the beginner will wish to know which to use.   For
objects requiring no higher  power than the one-inch object-glass,
the thicker kinds serve well  enough; for the half-inch the medium
thickness will be  required; while, for higher powers, the thinnest
covers must be used.   The " test-objects " for the highest powers
require to be brought so near to the object-glass that they admit
of the very thinnest covering only, and are usually mounted be-
twixt glasses which a beginner would not be able to use without
frequent  breakage; but  if these objects were  mounted with the
common  covers, they would be  really worthless with the powers
which they require to show  them satisfactorily.
  It  may be desirable to  know how such small  differences as
those betwixt  the various  thin  glass covers  can  be measured.
For  this purpose there  are  two or three sorts of  apparatus, all,
however, depending upon the same  principle. The description
of one,  therefore, will  be sufficient.  Upon a small stand is a
short metal lever  (as it may  be termed) which returns by a spring
to one certain position, where it is in contact with a fixed  piece
of metal.  At the other end this lever is connected with a  " fin-
ger," which  moves round a dial like that of a  watch, whereupon
are  figures at fixed distances.  When the lever is separated from
the  metal  which is stationary, the  other  end being  connected
with the  " finger  " of the dial, that " finger " is moved in propor-
tion to  the distance of the separation.   The thin glass is, there-
fore, thrust betwixt the end of the lever  and fixed metal, and each
piece is  measured by the figures on the dial in stated and  accu-
rate  degrees.  This kind of  apparatus, however, is expensive, and
when not at our command, the thin glass may be placed edge-
wise in the stage forceps, and measured very accurately with the
micrometer.
  Cleanliness with the thin glass is, perhaps, more necessary than
with the  slides, especially when  covering objects which are to be
used with a high  power; but it  is far more difficult to attain, on
account of the liability  to breakage.  The usual method of clean-
ing these covers  is as follows:—Two discs of wood, about two
inches in diameter, are procured, one side of each being perfectly
flat and covered with clean  wash-leather.   To  the  other side of 
OF MICROSCOPIC OBJECTS.
13
these a small knob is firmly affixed as  a handle, or where practi-
cable the whole may be made out of a solid piece.   In cleaning
thin glass, it should be placed betwixt the covered sides of the
discs, and may then be safely rubbed with  a  sufficient pressure,
and so cleaned on  both  sides  by the leather.  If, however, the
glass be greasy, as is sometimes the case, it must be first washed
with a strong solution of potash,  infusion of  nut-galls, or any  of
the  commonly used grease-removing liquids : and Avith some im-
purities water, with the  addition  of a few  drops of strong acid,
will be found very useful, but this last is not often required.
   The above method of  cleaning  thin glass should always  be
used by beginners;  but after some  experience the hand becomes
so  sensitive  that  the  above apparatus is often dispensed  with,
and the glasses, however thin, may be safely cleaned betwixt the
finger and  thumb  with  a  cambric handkerchief,  having  first
slightly damped the ends of the  fingers employed to  obtain firm
hold.  When the dirt is very obstinate, breathing upon the glass
greatly facilitates its removal, and the sense of touch becomes so
delicate that the breakage is inconsiderable ; but this method can-
not be recommended to  novices, as nothing but time spent in
delicate manipulation can give  the sensitiveness required.
   It was  before mentioned that  the ordinary glass slides were
sometimes  worthless,  especially  for fine objects, from having a
rough surface,  which presented  a  dusty appearance under  the
microscope.  This imperfection exists in some thin glass also, and
it is irremediable;  so that it is  useless to attempt to cleanse  it;
nevertheless, care should be taken  not to mistake dirty glass  for
this roughness, lest good glass  be laid aside for a fault which does
not belong  to it.
   When any object which it is desired to mount is of consider-
able  thickness, or will not bear pressure, it is evident that a wall
must be raised around it to support the thin glass—this is usually
termed a " cell."  There are various descriptions of these, accord-
ing to the  class  of objects they are required  to  protect; and
here may be given  a description  of those which  are  most gene-
rally used in mounting " dry " objects, leaving those required  for
the preservation of  liquids until we come to the consideration of
that mode of mounting.   Many  have made use' of  the following 
14
PREPARATION AND MOUNTING
slides.   Two pieces of hard  wood of the usual size (3 in. by 1
in.), not  exceeding one-sixteenth of an  inch in  thickness, are
taken, and a hole is then drilled in the middle of one of these of
the size required.   The  two pieces  are  then  united  by glue or
other cement, and left under pressure until thoroughly dry, when
the cell is fit for use.  Others substitute  cardboard for the lower
piece of wood, which is  less tedious, and  is strong enough for
every purpose.   This class  of  " cell" is,  of course,  fitted  for
opaque objects only where no light is required from below; and
as almost  all such are better seen when on  a  dark background,
it is usual to fix a small piece of black paper at the bottom of the
cell upon  which to  place them.    For very small objects  the
" grain"  which  all such paper has when  magnified  detracts a
little from the merit of this background; and lately I have used
a small piece of thin glass covered  on the  back with black var-
nish, and  placed the object upon the smooth untouched side.
   Another method of  making  these cells  is as follows:—Two
" punches," similar to those used for cutting " gun-wads," ar? pro-
cured, of  such sizes  that with  the  smaller  may be cut  out the
centre of the larger, leaving a ring whose side is not less than one-
eighth  of  an inch  wide.  These rings may be readily made, the
only difficulty being  to keep the  sides parallel;  but a little care
will make  this easy enough.   For this purpose  close-grained
cardboard may be conveniently used.  It must have a well-glazed
surface, else the varnish or cement used in affixing the thin glass
cover sinks into the substance, and  the adherence  is very imper-
fect.   When  this takes  place it  is easily remedied by brushing
over the surface of the cardboard a strong solution of gum or.isin-
glass; and this application, perhaps, closes  also the pores of the
card, and  so serves a double purpose.   But, of  course, the gum
must be perfectly dried before the ring is used.
   For  cardboard, gutta-percha  has  been substituted,  but cannot
be recommended, as it always becomes brittle after a certain time,
never adheres to the glass with the required firmness, and its shape
is altered when worked with even a little heat.   Leather is often
used, and is very convenient; it should be  chosen, however, of a
close texture, and  free from oil, grease, and all those  substances
which are laid upon it by the " dressers." 
OF MICROSCOPIC OBJECTS.                15
  Rings of cardboard, &c, have been rejected by persons of great
experience, because they are of such a nature that dampness  can
penetrate them.   This fault can be almost, if not totally, removed
by immersing them in some  strong varnish, such as the asphalt
varnish hereinafter mentioned; but they must be left long enough
when affixed to the glass slide to become perfectly dry, and  this
will require a much longer time than at first would  be supposed.
  There has, however, been lately brought out what is termed the
ivory cell.   This is a ring of  ivory-like substance, which may be
easily and firmly fixed to the glass slide by any of the commonly-
used  cements, and  so forms a beautiful cell for any dry objects.
They are made of different sizes,  and are not expensive.
  Sometimes slides  are used which are made by  taking a  thin
slip of wood of the  usual size (3 in.  by 1  in.), in  the centre of
which is cut a circular hole large enough to receive the object. A
piece of thin glass is fixed underneath the slide, forming a cell for
the object, which may then be covered and finished like an ordi-
nary slide.   This has the  advantage  of serving for  transparent
objects for which the before-mentioned wooden slides are unsuita-
ble.   A slight modification of this plan is often used where the
thickness of the objects is inconsiderable, especially with some of
the Diatomacese,  often termed "test-objects."   The wooden slide
is cut with the central opening as above, and two  pieces of  thin
glass are laid upon it, betwixt which the diatoms or other objects
are placed, and kept  in their proper position by a paper cover.
This arrangement is a good one, insomuch as the very small  por-
tion of glass through which the light passes' on its way to the mi-
croscope from the reflector causes the refraction or interference to
be reduced to the lowest point.
  A novice would naturally think the appearance of some of the
slides above mentioned very slovenly and unfinished; but they are
often covered with ornamental papers, which may be procured at
almost every optician's, at a cost  little more than nominal, and of
innumerable patterns  and colours.  How to use these will  be de-
scribed in another place.
  It is very probable that a  beginner would ask his friend what
kind of slides he would advise him to use.  Almost all those made
of wood are liable to warp more or less, even when the two pieces 
16
PREPARATION AND MOUNTING
are separate or of different kinds; those of cardboard and wood
are generally free from this fault, yet the slides, being opaque, pre-
vent the employment of the Lieberkuhn.   To some  extent  glass
slides, when covered with ornamental papers, are liable to the same
objection, as the light is partly hindered.  And sometimes the
dampness from the paste, or other substance used to affix the pa-
pers, penetrates to the object, and so spoils it, though this may be
rendered less frequent by first attaching the thin glass to the slide
by some harder cement.   Much time, however, is taken up by the
labour of  covering the slides, which is a matter of consideration
with some.  Certainly, the cost of the glass slides was formerly
great;  but now they are reasonable enough in this respect, so that
this objection is  removed.  It is, therefore, well to use glass slides,
except where the thin glasses are employed for tests, <fec, as above.
When the thin  glass circles are placed upon the slides, and the
edge is varnished with black or coloured  rings, the appearance of
finish is perfect.   The trouble is much  less than with most of the
other methods, and the illumination of the object very slightly in-
terfered with.
  To varnish  the  edges  of these  covers, make circles of any
liquid  upon the glass  slide, and perform any other " circular"
work mentioned hereafter, the little instrument known as " Shad-
bolt's turntable " is almost indispensable.   It is made as follows :
—At one end of a  small piece of hard  wood is fixed an  iron
pivot about one-eighth inch  thick, projecting  half an inch from
the wood, which serves as a centre upon which a round  brass
table three inches  in diameter  revolves.   On  the surface of this
are two springs,  about one and  a half  inches apart,  under which
the slide is forced and  so kept in position, whilst the central part
is left open to  be worked upon.  The centre is marked, and two
circles half an  inch and one inch in diameter are usually deeply
engraved upon the table to serve as guides in placing the  slide,
that the ring  may  be drawn  in the right position.  When the
slide is placed upon  the " table" underneath the springs, a camel-
hair pencil is filled with the varnish, or other  medium used, and
applied to the surface of the glass; the table is then made to
revolve, and a circle is consequently  produced, the diameter of
which it is easy  to regulate. 
OF MICROSCOPIC OBJECTS.
17
  Many objects for the microscope may be seriously injured by
allowing the fingers  to  touch them—many more are so minute
that they cannot  be  removed in  this way at all, and often it is
necessary to take from  a mass of small grains, as in sand, some
particular particle.  To accomplish this, there  are two  or three
contrivances recommended : one by means of split bristles, many
of which will readily be found in any shaving brush  when it has
been well used.  The bristles when pressed upon any hard surface
open, and when the pressure is removed close again with  a spring;
but the use of these  is  limited.   Camel-hair pencils  are of great
service for this  and many  other purposes to  the microscopist.
In very fine work they are  sometimes required so small that all
the hairs with the exception of one or two finer pointed ones are
removed.   A few of  various sizes should always be kept on hand.
  Equally necessary are fine pointed needles.   They  are very
readily put up for use by thrusting the " eye" end into a common
penholder, so as to be firm.   The points may be readily renewed,
when injured, on a common  whetstone; but when out of use
they may be protected by being thrust into a piece of cork.
  Knives of various kinds  are  required in some  branches of
microscopic work, but these will be described where " dissection,"
(tc, is treated at  some length, as also various forms of scissors.
In  the most simple objects, however, scissors  of the usual kind
are necessary.   Two or three sizes  should always  be kept on
hand, sharp and in good order.
  A set of glass  tubes, kept in  a case of some  sort to prevent
breakage, should form part  of  our "fittings"  and be  always
cleaned immediately after use.  These are generally from  six to
ten inches long and  from one-eighth to  a quarter of an inch in
diameter.  One  of these should be straight and equal in width at
both ends;  one  should be  drawn out gradually to a fine point;
another should be pointed as the last, but be  slightly  curved at
the compressed  end, in order to  reach points otherwise unattain-
able.  It is  well to have  these  tubes of various widths at the
points, as in some waters the finer would be inevitably stopped.
For other purposes the fine ones are very useful,  especially in the
transfer of " preservative liquids," which will  come  under  notice
in another chapter.
                              2* 
18              PREPARATION AND MOUNTING
  Forceps are required in almost all microscopic manipulations,
and consequently are scarcely ever omitted from the microscopic
box, even the most meagrely furnished; but of these there are
various  modifications, which  for certain purposes  are more con-
venient  than the usual  form.   The ordinary metal ones are em-
ployed  for taking up small objects, thin  glass, etc.; but when
slides are to be held over a lamp, or in any position where the
fingers cannot conveniently be  used, a different instrument must
be found.  Of these there are many kinds ; but Mr. Page's wooden
forceps  serve the purpose very well.  Two pieces of elastic wood
are strongly bound together at one  end,  so that they  may  be
easily opened at the  other, closing again by their  own elasticity.
Through the  first of these pieces is loosely passed a brass  stud,
resembling a small screw, and fastened in the second, and  through
the second a similar stud is taken and fixed in the first—so that
on pressure of the studs  the two strips of wood  are opened to
admit  a slide  or  other object  required to be held in  position.
The wood strips are generally used three or four inches long, one
inch wide, and about one-eighth inch thick.
   Again, some objects when placed  upon the glass slide are of
such an elastic nature that no  cement will secure the thin glass
covering until it becomes hard.   This difficulty may be overcome
by various methods.   The following  are  as good and simple as
any.  Take two pieces of wood about two  inches long, three-
quarters wide, and one-quarter  thick; and a small rounded piece
one inch long and one-quarter  in diameter;  place this latter be-
twixt the two larger pieces.   Over one end of the  two combined
pass an india-rubber band.   This will give a continual pressure,
and may  be  opened by bringing the two  pieces together at
the other end; the pressure may  be readily made uniform  by
paring the points at the inner sides, and may be regulated by the
strength  of the india-rubber band.  These bands  may  be made
cheaply, and of any power, by procuring a piece of india-rubber
tubing  of the  width  required,  and cutting off certain breadths.
Another very simple method  of getting this pressure is mentioned
in the  " Micrographic Dictionary."  Two pieces of whalebone of
the length  required are tied together firmly at each end.  It is
evident  that any  object placed betwixt them will be subject to 
OF MICROSCOPIC OBJECTS.
19
continual pressure.   The power  of  this may be  regulated  by
the thickness and  length of the  whalebone.  This  simple con-
trivance is very useful.
   Common watch-glasses should always be kept at hand.  They
are certainly the cheapest, and their transparency makes them
very convenient reservoirs in which objects may be steeped in any
liquid ;  as it saves much trouble to examine cursorily under the
microscope, when the air-bubbles  are expelled from insects, etc.,
etc.  They  are  readily  cleaned, and  serve very well as covers,
when turned upside down,  to protect any objects from the dust.
For this latter purpose  Dr. Carpenter recommends the use of a
number of bell-glasses, especially when one object must be left for
a time (which often happens)  in order  that another may be pro-
ceeded with. Wine glasses, when the " legs" are broken, may thus
be rendered very useful.
   As heat is necessary in mounting many objects, a lamp will be
required.   Where gas is used, the small lamp known as " Bun-
sen's"  is  the most convenient  and inexpensive.   It gives great
heat, is free from smoke, and is readily affixed to the common
gas-burner by a few feet of india-rubber tubing.  The light from
these lamps is small, but this is little or no drawback to their use.
Where gas is not available, the common spirit-lamps may be used,
which are very clean and answer every purpose.
   In applying the required heat  to  the slides, covers, &c, it is
necessary in  many cases to ensure uniformity, otherwise there is
danger of the glass being broken.  For this purpose a brass plate
at least three inches wide, somewhat longer, and one-eighth of
an inch thick, must be  procured.  It should then  be affixed to a
stand, so that it  may be readily moved higher or lower,  in order
that  the  distance from  the lamp may be changed at will,  and
thus the degree of heat more easily regulated.  This has also the
advantage of enabling the  operator to allow his  slides,  &c, to
cool  more gradually, which, in  some  cases, is absolutely neces-
sary,—as in fusing some of the salts, &c.
   In order  to get  rid  of air-bubbles, which are frequently  dis-
agreeable  enemies to the mounter of objects, an air-pump is often
very useful.   This is  made  by covering a circular plate of metal
with a  bell-glass,  both of which are ground so finely at the edges 
20
PREPARATION  AND MOUNTING
that greasing the place of contact renders it air-tight.  The pump
is then joined  to  the metal plate underneath, and'worked with a
small  handle like a common syringe.  By turning a small milled
head  the air may be allowed  to  re-enter when it is required to
remove the bell-glass and examine or perform any operation upon
the object.   The mode of using this' instrument will be described
hereafter, but  it may be here stated  that substitutes have been
devised for this useful apparatus ;  but  as it is now to be obtained
at a low cost, it is hardly worth while to consider them.   Much
time  is, in  many  instances, certainly saved by its  use, as a very
long  immersion in  the  liquids would be required to expel the
bubbles, where the air-pump would remove them in an hour.
   The next thing  to be considered is what may  be termed
Cements, some of which are necessary  in every method of mount-
ing objects for the microscope.  Of these will be given the com-
position where it  is  probable the  young student can make use of
it; but many of them are so universally kept as to be obtainable
almost anywhere; and when  small quantities only are required,
economy suffers more from  home manufacture than from paying
the maker's profit.
   Amongst these, Canada Balsam  may, perhaps, be termed the
most  necessary, as  it is generally used for  the  preservation of
many transparent  objects.  It  is  a  thick  liquid  resin of a light
amber colour, which on exposure to the  atmosphere becomes dry
and hard  even to brittleness.  For this reason it is seldom used
as a  cement alone where the  surface  of contact  is small, as  it
would be apt to be displaced by any sudden shock, especially
when old.  In the  ordinary method of  using, however, it  serves
the double purpose of preserving the object and fixing the thin
glass  cover; whilst  the  comparatively large space upon  which it
lies lessens the risk of displacement.   By keeping, this substance
becomes thicker; but a very little warmth will render it liquid
enough to use even when  to  some extent this change has taken
place.  When heated, however, for some time and allowed to
cool,  it  becomes  hardened  to any degree, which may be readily
regulated by the  length of time it has been exposed, and the
amount of heat to which it has been subjected.  On account of
this  property  it  is  often used with  chloroform : the balsam is 
                   OF MICROSCOPIC OBJECTS.                 21

exposed to heat until, on cooling, it assumes a glassy appearance ;
it  is then  dissolved in  pure chloroform until it becomes of the
consistence  of  thick  varnish.  This liquid is very convenient in
some cases; as air-bubbles are much more easily got rid of than
when undiluted Canada  balsam is used.  It also dries readily, as
the chloroform evaporates very quickly, for which reason it must
be preserved in a closely-stoppered bottle.  It has been said that
this mixture becomes cloudy with long  keeping, but I have not
found it  so in any cases where I have used it.  Should it, how- ,'
ever, become  so,  a  little  heat will readily dispel  the  opacity.,
The ordinary balsam, if  exposed much  to the  air whilst being ^
used, becomes thicker,  as has been already stated.  It may be -,
reduced  to the required  consistency with common turpentine,
but I have often found this in some degree injurious to the trans-
parency of the balsam, and the amalgamation of the two is by no
means perfect.  (See  also Chapter III.)  The cheapness  of  the
article renders it  no  extravagance  to  use it  always undiluted;
and when preserved in a bottle with a hollow cover fitting tightly
around the neck, both surfaces being finely ground, it remains fit
for use much longer than in the ordinary jar.
   Asphaltum.—This substance is dissolved in linseed oil, turpen-
tine, or naphtha,  and is  often termed  " Brunswick black."  It is
easily  worked, but is not generally deemed a trustworthy cement,
as after a time it is readily loosened from its ground.  It is, how-
ever, very  useful for some purposes  (such  as " finishing"  the
slides), as it dries quickly.  I shall, however, mention a modifica-
tion of this cement a little further on.
   Marine Glue.—No cement is more useful or trustworthy for
certain purposes than this.   It is made in various proportions;
but one really good mixture is—equal parts of india-rubber and
gum shellac;  these  are  dissolved in mineral naphtha with heat.
It is, however, much better to  get it from the  opticians or others
who keep it.  It requires heat in the application, as will be explained
in  Chapter IV.; but it is soluble in few, if any, liquids used by the
microscopist, and for that reason is serviceable in the manufacture
of cells, &c.   Where two pieces of glass are to be firmly cemented
together, it is  almost  always employed;  and in all glass troughs,
plates with ledges, &c, thq beginner may find examples of its use. 
22
PREPARATION AND MOUNTING
  Gold  Size.—This substance may always be  procured at any
colourman's shop.  The process of its preparation is  long and
tedious.   It is, therefore, not necessary to describe it here.  Dr.
Carpenter says that it  is very  durable,  and may be used with
almost any  preservative liquids, as  it is acted upon by very few
of them, turpentine being  its only true  solvent.  If too  thin, it
may be exposed for awhile  to the open air, which by evaporation
gradually thickens it.   Care must be taken, however, not to ren-
der it too thick, as it will then be useless.   A small quantity should
be kept on hand,  as it is much more adhesive when old.
  Liquid Glue is another of these cements,  which is  made by
dissolving gum shellac in naphtha in such quantity that it may be
of the required consistency.  This cement  appears to me almost
worthless in ordinary work, as its adherence  can never be relied
upon ; but it is so often used and recommended  that an enumera-
tion of cements might be deemed incomplete  without it.   Even
when employed simply for varnishing the outside  of  the glass
covers, for appearance'  sake alone,  it invariably chips.   Where,
however, oil is used as a preservative liquid, it serves very well to
attach the thin glass;  but  when  this is accomplished, another
varnish less liable to " chip " must always be laid upon it.  (See
Chapter  IV.)
  Black Japan.—This  is prepared  from oil of turpentine, linseed
oil,  amber, gum anime,  and asphalt.  It is troublesome to make,
and therefore it is much better  to procure it at the shops.  It is
a really good cement, and  serves very well to make  shallow cells
for liquids, as will be described in Chapter IV.   The finished cell
should be exposed for a short time to the heat of what is usually
termed a  " cool oven."  This renders it very durable, and many
very careful manipulators make use  of it for their preparations.
  Electrical Cement.—This will be found very good for some
purposes hereinafter described.   To make it melt together—
                    5  parts of resin.
                    1   "     beeswax.
                    1   "     red ochre.*

  * Dr. Griffiths says that the addition of 2 parts of Canada balsam renders
this cement much more adhesive to the glass. 
OF MICROSCOPIC OBJECTS.
23
It must be used whilst hot, and as long as it retains even  slight
warmth can be readily moulded into any form.  It is often em-
ployed in making shallow cells for liquids, as before mentioned.
  Gum-Water is  an article which  nobody should ever be with-
out ; but  labels, or  indeed any substance, affixed to glass with
common  gum, are  so liable to leave it spontaneously, especi-
ally when kept very dry, that I have  lately added five or six drops
of glycerine to an  ounce of the gum  solution.   This addition has
rendered it very trustworthy even on glass, and now  I  never use
it without.  This solution cannot be  kept  long without undergo-
ing fermentation, to prevent which the addition of a small  quan-
tity of an essential oil (as oil of cloves, &c.,) or one-fourth  of its
volume  of alcohol, may be made, which will not interfere in any
way with its use.
  There is what is sometimes termed an extra adhesive gum-water,
which  is  made with the addition of isinglass, thus:—Dissolve
two drachms of isinglass in four ounces of distilled vinegar; add
as much gum arabic as will give it  the required consistency. This
will keep  very well, but is apt to become  thinner,  when  a little
more gum may be added.
  All these, except one  or two, are liquid, and must be kept in
stoppered bottles, or, at least, as free from the action of the  air as
possible.
  When  any  two  substances  are to  be united   firmly, I have
termed the medium employed " a cement;" but often the appear-
ance of  the slides is  thought to be improved  by drawing  a
coloured ring upon them, extending partly on the cover and partly
on the slide, hiding the junction of  the two.   The medium used
in these cases I term a Varnish, and hereinafter mention one or
two.  Of course, the tenacity is not required to be so perfect as
in the cements.
  Sealing-wax Varnish is prepared by coarsely powdering seal-
ing-wax, and adding spirits of wine;  it is then digested at a gen-
tle heat to the required thickness.  This  is very frequently used
to " finish " the slides, as before mentioned, and can  easily be made
of any colour by employing different kinds of sealing-wax;  but is
very liable to " chip " and leave the glass.
  Black Varnish is readily prepared by adding a small quantity 
24               PREPARATION  AND MOUNTING

of lamp-black to gold-size and mixing intimately.   Dr. Carpenter
recommends this as a good finishing varnish, drying quickly and
being free from that brittleness  which renders some of the others
almost worthless; but it should not  be used in the first process
when mounting objects in fluid.
  Amongst these different cements and varnishes I worked a long
time  without coming to any decision as to  their  comparative
qualities, though making innumerable experiments.   The harder
kinds were continually cracking, and the softer possessed but lit-
tle adhesive power.  To  find hardness  and adhesiveness  united
was my object, and the following possesses these  qualities  in  a
great degree:—
               India-rubber........   \  drachm.
               Asphaltum.........   4  oz.
               Mineral naphtha.....  10  "

Dissolve the  india-rubber in the naphtha, then add the asphaltum
—if necessary heat must be employed.
   This is often used by photographers as a black varnish for glass,
and never cracks, whilst  it is  very adhesive.  Dr. Carpenter, how-
ever,  states that his experience has not been favourable to it; but
I have used it in great quantities and have never found it to  leave
the glass in a single instance  when used in the above proportions.
The  objections to it are, however, I think easily explained, when
it is known that there are many kinds of pitch,  &c, from coal,
sold by the name of asphaltum, some  of  which are worthless in
making a microscopic cement.   When used for this purpose, the
asphaltum must be genuine and of  the  best quality that can be
bought.   The  above mixture serves  a double purpose—to unite
the cell to the slide, and also as a " finishing " varnish.  But it is
perhaps more convenient to have two bottles of this  cement, one
of which is thicker  than common varnish, to use for uniting the
cell, &c.;  the other liquid enough to flow readily, which may be
employed  as a surface varnish in finishing the slides.
   The brushes or camel-hair  pencils should always  be  cleaned
after use ;  but with the  asphalt varnish above mentioned it is suf-
ficient to wipe off as carefully as possible  the superfluous quantity
 which adheres to the pencil,  as, when again made use of, the var- 
OF MICROSCOPIC OBJECTS.
25
nish will readily soften it;  but, -of course, it will be necessary to
keep separate brushes for certain purposes.
  Here it may  be observed that every object should be labelled
with name and any other descriptive item  as soon  as mounted.
There are many little differences in the methods of doing this.
Some write with a diamond upon the slide itself; but this has the
disadvantage of being not so easily seen.  For this reason a small
piece of paper is usually affixed to one end of the slide, on which is
written what is required.   These labels may be bought of different
colours and designs ; but the most simple are quite as good, and
very readily procured.   Take  a sheet of thin writing paper and
brush over one side a strong solution of gum, with the addition of
a few drops of glycerine as above  recommended;  allow this to
dry, and then with a  common  gun-punch stamp out the circles,
which  may be affixed to the slides by simply  damping the gummed
surface, taking  care to write the required name, etc., upon it  be-
fore damping it, or else allowing it to become1 perfectly dry first.
  ■There is one difficulty which a beginner often experiences  in
sorting and mounting certain specimens under  the microscope,
viz., the inversion of the  objects;  and  it is  often  stated  to be
almost impossible to work without an erector.  But this difficulty
soon vanishes, the young student becoming  used to working what
at first seems in contradiction to his sight.
   Let  it be understood,  that  in giving  the description  of those
articles which are usually esteemed  necessary in the various parts
of  microscopic manipulation,  I  do  not mean to say that without
many of these  no work of any value can be done.   There  are, as
all will allow, certain forms of apparatus which aid the operator
considerably; but the cost may be too great for him.  A little
thought, however, will frequently overcome  this  difficulty, by ena-
bling him  to make, or get made, for himself, at a  comparatively
light expense,  something  which will  accomplish all he desires.
As an example of this, a friend of  mine made what he terms his
" universal stand," to  carry various condensers, etc., etc.,  in  the
following way:—Take a steel or brass  wire, three-sixteenths  or
one-quarter inch thick and six or eight inches long; " tap" into a
solid, or make  rough and  fasten with melted lead into  a hollow,
ball.  (The foot of a  cabinet or work-box answers the purpose 
26
PREPARATION AND MOUNTING
very well.)  In the centre of a round piece of tough board, three
inches in diameter, make a hemispherical cavity to fit half of the
ball, and bore a hole through  from the middle  of this cavity, to
allow the wire to pass.  Take another  piece of board, about four
inches in diameter, either round or square, and  one-and-a-half or
two inches thick, make a similar cavity in its centre to receive the
other half of the ball, but only so deep as to allow the ball to fit
tightly when the two pieces of board are screwed together, which
last operation must be done with three or four  screws.   Let the
hole for the wire in the  upper part be made  conical (base up-
wards), and so large  as  only to prevent  the ball from escaping
from its socket, in order that the shaft may move about as freely
as possible.   Turn a cavity, or make holes, in  the bottom of the
under piece,  and fill  with lead to give weight and  steadiness.
This, painted green bronze and varnished,  looks  neat; and by
having pieces of  gutta-percha tubing to fit the shaft,'a great vari-
ety of apparatus may be attached to it.
   Again, a " condenser"  is  often required for the illumination-of
opaque objects.   My ingenious friend uses an " engraver's bottle"
(price 6d.), fills it with water, and suspends it betwixt the light
and the object.   Where the  light is  very yellow,  he tints the
water with indigo, and so removes the  objectionable  colour.
   I merely mention these as examples  of what may be done by a
little thoughtful contrivance, and to remove the idea that nothing
is  of much  value save that which is  the work of professional
workmen, and consequently expensive. 
OF MICROSCOPIC OBJECTS.
21
                   CHAPTER  II.

           TO PREPARE AND MOUNT OBJECTS  " DRY."

The term  " dry " is used when the object to be mounted is not
immersed in any liquid or medium, but preserved in  its natural
state, unless it requires cleaning and drying.
  I have before stated that thorough cleanliness is necessary in
the mounting of all microscopic  objects.  I may here add that
almost every kind of substance used by the microscopist suffers
from careless handling.  Many leaves with fine hairs are robbed
of half their beauty, or the hairs, perhaps, forced into totally dif-
ferent shapes and  groups;  many insects lose their  scales, which
constitute their chief value to the microscopist; even the glass
itself distinctly shows  the marks  of the  fingers if left  uncleaned.
Every object must also  be thoroughly dry, otherwise  dampness
will arise and become  condensed  in small  drops upon  the inner
surface of  the thin glass cover.   This defect is frequently met
with in slides which have been mounted quickly; the objects not
being thoroughly  dry when enclosed in the  cell.  Many of the
cheap slides are thus  rendered worthless.  Even  with  every care
it is not possible to get rid of this annoyance occasionally.
  For the purpose of mounting opaque objects " dry," discs were
at one time very commonly made use of.   These are  circular
pieces of cork, leather, or other soft  substance, from one-quarter
to half an  inch  in diameter, blackened  with  varnish or  covered
with black paper, on which the object is  fixed  by gum or some
other adhesive substance.  They are usually  pierced longitudi-
nally by a strong pin, which serves for the forceps to lay hold of
when being placed under the microscope for examination.   Some-
times objects are affixed  to both  sides of the disc, which is rea-
dily turned when under the  object-glass.   The advantage of this
method of  mounting  is the ease with  which the disc may  be 
28
PREPARATION AND  MOUNTING
moved, and so present  every part of the object to the  eye save
that by which it is fastened to the disc.  On this  account it is
often  made  use of when  some particular subject is undergoing
investigation, as a number of specimens may be placed upon the
discs with very little labour, displaying all the parts.  But where
exposure to the atmosphere or small particles of  dust will  injure
an object, no advantage which the discs may possess should be
considered, and an  ordinary covered  cell should be employed.
Small pill-boxes have be.en  used, to the bottom of which a piece
of cork has been glued to  afford  a ground for the pin or other
mode of  attachment; but this is liable to some of the same faults
as the disc, and it  would be unwise to use these for permanent
objects.
   Messrs. Smith and  Beck have lately invented,  and are now
making,  a beautiful small  apparatus, by means  of which the disc
supporting the object can be worked with little or no trouble into
any position  that may prove most convenient, whilst a perforated
cylinder  serves for the reception of  the  discs when out of use,
and fits into a case to protect them from dust.  A pair  of forceps
is made for the express purpose of removing them from the case
and placing them in the holder.
   All dry objects, however, which are to  be preserved  should be
mounted on glass  slides in one of the  cells (described in Chapter
I.) best suited to  them.   Where the object  is  to be  free from
pressure, care must be  taken that the cell is deep enough to en-
sure  this.  When  the depth required is but  small, it is  often
sufficient to omit the card, leather, or  other circles, and with the
"turn-table"  before described, by means of a thick varnish and
camel-hair pencil, to form a ring of the  desired depth; but
should the varnish not be of sufficient substance to  give  such
" walls " at once, the first  application may be allowed to dry, and
a second made upon it.  A number  of these may be prepared at
the same time, and laid by for  use.   When liquids are used (see
 Chapter IV.), Dr. Carpenter recommends gold-size as  a good
varnish for the purpose, and this may be used in " dry" mountings
 also.   I have used the asphaltum and india-rubber (mentioned in
 Chapter I.),  and  found it to be everything I could wish.  The
 cells, however, must be thoroughly dry, and when they will bear 
OF MICROSCOPIC OBJECTS.
29
the heat they should be baked for an hour at least in a tolerably
cool oven, by which treatment  the  latter  becomes  a first-rate
medium.  All dry objects which will not bear  pressure must be
firmly fastened to the slide, otherwise the necessary movements
very often injure them, by destroying the fine hairs, &c.    For
this purpose  thin varnishes are very often  used, and will serve
well enough for large objects, but many smaller ones are lost by
adopting  this plan, as for a time, which may be  deemed  long
enough to harden the  varnish,  they exhibit no defect, but  in a
while a " wall"  of  the plastic gum gathers around them, which
refracts the light, and thus leads the student to false conclusions.
In all finer work, where it is necessary to  use any method of fix-
ing them to the  slide, a solution of common gum, with the addi-
tion of  a few  drops  of glycerine (Chapter  I.), will be found to
serve the purpose perfectly.  It must, however, be carefully filtered
through blotting paper, otherwise the minute particles  in the
solution interfere with the object, giving the slide a dusty appear-
ance when under the microscope.
   When mounting an object in any of these cells, the glass  must
be thoroughly cleaned, which  may be done with a cambric hand-
kerchief, after the washing mentioned in Chapter I.  If the object
be large, the  point of a fine camel-hair pencil  should be  dipped
into the gum solution, and a minute quantity of the liquid depo-
sited in the cell where the object is to be placed, but not to cover
a  greater surface than the  object  will totally hide  from sight.
This drop of gum must be allowed to dry, which will take a few
minutes.   Breathe then upon  it two  or three  times,  holding the
slide not far from the mouth, which will  render the surface adhe-
sive.   Then  draw a  camel-hair pencil through the lips, so as to
moisten it slightly (when anything small will  adhere  to it  quite
firmly  enough), touch the object  and place it upon the  gum in
the desired position.   This must be done immediately to ensure
perfect stability, otherwise the gum will become at least partially
dry and only retain the object imperfectly.
   When, however, the objects are so minute that it would be im-
possible to deposit atoms of gum small enough for each one to
cover,  a different method of proceeding must be adopted.   In this
ease a small  portion of the  same gum solution should be placed 
30
PREPARATION AND  MOUNTING
upon  the  slide, and  by means  of any small  instrument—a long
needle will serve the purpose very well—spread over the surface
which will be required.  The quantity thus extended will be very
small, but by breathing upon it may be prevented drying whilst
being dispersed.  This, like the forementioned, should be then al-
lowed to dry; and whilst the objects are being placed on the pre-
pared surface, breathing upon it as before will restore the power of
adherence.
  When gum  or  other liquid cement has been used to fix the
objects to the glass, the thin  covers must not be applied until the
slide has been thoroughly dried, and all fear of dampness arising
from the use of the  solution done away with.  Warmth  may be
safely applied for the purpose, as objects fastened by this method
are seldom, if ever, found to be loosened by it.  As  objects are
met with of every thickness,  the cells will be required of different
depths.  There  is no- difficulty in accommodating ourselves in
this—the deeper cells may be readily cut out  of thick  leather,
card,  or other substance preferred (as mentioned in Chapter I.).
Cardboard is easily procured of almost any thickness; but some-
times it is convenient  to find a thinner substance even than this.
When thin glass is laid upon a drop of any liquid upon a slide,
every one must  have observed how readily the liquid spreads be-
twixt the two:  just so when  any thin varnish is used  to surround
an object of little substance, excessive care is needed lest the varnish
should extend betwixt the cover and slide, and so render it worth-
less.   The slightest wall, however, prevents this from taking place,
so that a ring of common paper may be used, and serve a double
purpose where the objects  require no deeper cell than this forms.
   Many objects, however,  are of such  tenuity—as the leaves of
many mosses, some  of the Diatomaceae,  scales of insects, &c.—
that no cell is requisite excepting that which is necessarily formed
by the medium  used to attach the thin glass cover to  the slide;
and where the slide is covered by the ornamental papers mentioned
in Chapter I., and pressure  does not injure the object, even this
is omitted, the thin glass being kept in position by the cover; but
slides mounted in this manner are frequently injured by dampness,
which soon condenses upon the inner surfaces and interferes both
with  the object and the clearness of its appearance. 
OF MICROSCOPIC OBJECTS.
31
   The thin glass, then, is to be united to the slide, so as to form
 a perfect protection from dust, dampness, or other injurious mat-
 ter, and  yet allow a thoroughly distinct view of the object.  This
 is to be  done by applying to the glass slide round the object some
 adhesive substance, and with  the forceps placing the thin glass
 cover (quite dry and clean) upon it.   A gentle pressure round the
 edge will then ensure a perfect adhesion, and with ordinary care
 there will  be little or no danger of breakage.   For this  purpose
 gold-size is frequently used.   The asphalt and india-rubber varnish
 also will be found both  durable  and serviceable.   Whatever
 cement  may be used, it is well to  allow it to become  in some
 measure " fixed " and dried; but where no cell or  " wall" is upon
 the slide, this is quite necessary, otherwise the varnish will be al-
 most certain to extend, as before mentioned, and ruin the object.
 It may be stated here that gold-size  differs  greatly in its drying
 powers, according to its age, mode of preparation, &c.  (Chap-
 ter IV.)
   Should any object be enclosed which requires  to be kept flat
 during the drying of the cement, it will be necessary to use some
 of the contrivances mentioned in Chapter I.
   When the slide is thus far advanced,  there remains the " finish-
 ing" only.  Should the student, however, have no  time to com-
 plete his work  at  once, he  may safely leave it at  this stage until
 he has a number of slides which he may finish at the same time.
 There are different methods of doing this, some of which may be
 here described.
   If ornamental papers  are  preferred, a small circle  must be  cut
 out from the centre a little less than the thin glass  which covers
the object.  Another piece of coloured paper is made of the same
size, and a similar  circle taken from  its centre also, or both may
be cut at  the  same time.  The slide is then covered round  the
edges with paper of any plain colour, so that it may extend about
one-eighth of an inch over the glass on every side.  The orna-
mental paper is then pasted on the " object" surface  of the glass,
so that the circle shows the  object as nearly in the centre as pos-
sible, and covers the edges of the thin glass.  The  other coloured
paper is  then affixed underneath with  the circle coinciding with
that above.  And here I may observe, that  when this method is 
32               PREPARATION AND MOUNTING

used  there  is  no necessity  for  the edges  of the slide  to be
" ground," as all danger of scratching, &c, is done away with by
the paper cover.
  Many now use  paper covers, about one and a half inches long,
on  the upper side of the slide  only, with the centre cut out as
before, with no other purpose than that of hiding the edge of the
thin glass where it is united to the slide.
  The method of " finishing," however, which  is mostly used at
the present time, is to lay a  coating of varnish  upon the edge of
the thin glass, and extend it some little way on the slide.   When
a black circle is required,  nothing serves the purpose better than
the gold-size and lampblack, or the asphalt and india-rubber var-
nish, neither of which is  liable to chip ; but wThen used for this,
the latter should be rather thinner, as before advised.   Some of
these  varnishes are preferred of  different colours,  which may be
made  by using  the different kinds of sealing-wax,  as described in
Chapter I.;  but they are  always  liable to the defects there men-
tioned.   This circle cannot be made in any other way but by one
of those  contrivances which have now centred in Shadbolt's turn-
table.   A very  little practice will  enable the  young  student to
place  his slide so that the  circle may be uniform with the edge of
the thin glass.
  The slide  is now complete, except the addition of the name
and any  other particulars which  may be desirable.  For this
purpose one of the methods described in  Chapter  I. must be
employed.
  Amongst  the various classes of microscopic objects now receiv-
ing general attention, the Diatomaceas may be placed in a promi-
nent  position.   They  afford endless  opportunities of research,
and some very elaborate works have already been issued concern-
ing them.  Professor Smith's may be mentioned as one contain-
ing, perhaps, the best illustrations.  The young student may wish
to  know  what a  diatom  is.   The "Micrographic Dictionary"
gives  the following  definition:—" A family of confervoid  Algse,
of very peculiar character, consisting of microscopic brittle  organ-
isms."  They are now  looked upon by almost all of our scientific
men as belonging to the vegetable kingdom, though some few still
assign them to the  animal.  They are almost  invariably exceed- 
OF MICROSCOPIC OBJECTS.                33
ingly small, so that the unaided  eye can perceive nothing on a
prepared  slide of these organisms but minute dust.  Each sepa-
rate  portion, which is  usually seen when mounted, is  termed a
" frustule," or " testule :" this consists of two similar parts, com-
posed of  silica, between and  sometimes around which is a mass
of viscid  matter  called the " endochrome."   They are found in
almost  every  description  of  water,  according to the  variety:
some prefer sea-water,  others fresh, and many are seen nowhere
but in that which is a mixture of both, as the mouths of rivers, &c.
Ditches, ponds, cisterns, and indeed almost every reservoir, yield
abundance of these forms.  They are  not, however, confined to
" present" life ;  but, owing to the almost indestructible nature of
their siliceous covering, they are found in a fossil state  in certain
earths in great abundance, and are often termed " fossil Infusoria."
Upon these frustules are  generally to be seen lines, or " mark-
ings," of  different  degrees of minuteness, the delicacy of which
often serves the  purpose  of  testing the defining power of the
object-glasses.   Some  of  the  frustules  are triangular, others cir-
cular, and, indeed, of almost  every conceivable shape, many of
them presenting us with exquisitely beautiful designs.
  The markings, however, are seldom seen well, if at all, until the
frustules are properly prepared, the different methods of accom-
plishing which will be given a little further on.
  The collection of the fresh diatoms is  so closely connected with
their preservation, that a few notes may be given upon it before
we pass on.   For this purpose a number of small bottles must be
provided,  which may be placed in a tin box, with a separate apart-
ment for each, so that all chance of breakage may be done  away
with.  The  diatoms are generally of a  light brown colour; and
where they are observed in  the water, the bottle may be so placed,
with the mouth closed by the finger, that when the finger is with-
drawn the water will rush in, carrying the diatoms also.  If they
are  seen upon plants, stones,  or any other substance, they may
generally be detached and placed in the bottle.   When there is
a green  covering  upon the surface of the water, a great quantity
of diatoms is usually  found amongst it; as also upon the surface
of the mud in those ponds where they abound.  In these cases, a
broad flat spoon will be found verv useful, and one is now made
                              3 " 
34
PREPARATION AND  MOUNTING
 with a covering upon the broader  portion of it  to  protect the
 enclosed matter from being so readily carried off whilst bringing
 it to the surface again.   Where there is any depth of water, and
 the spoon will not reach the surface of the mud, the bottle  must
 be united to a long rod, and being then carried through the upper
 portion with the mouth downwards, no water will be received into
 it; but on reaching the  spot required,  the bottle-mouth may be
 turned up, and thus  become filled with what is nearest.
   From the stomachs of common fish—as the cod, sole, haddock,
 &c.—many specimens  of Diatomaceae  may be  obtained,  but
 especially  from the crab,  oyster, mussel,  and  other  shellfish.
 Professor Smith states that from these curious receptacles he has
 taken some with which he  has not elsewhere met.   To remove
 them from any of the small shell-fish, it is necessary to  take the
 fish or stomach from the shell, and immerse it in strong hot acid
 (nitric is the best) until the animal matter is dissolved, when the
 residue must be washed and treated as the ordinary Diatomaceae
 hereinafter described.
   Many diatoms are seen best when mounted in a dry state, the
 minute markings becoming much more indistinct if immersed in
 liquid or balsam ; and for this reason those -which are used as test
 objects are usually mounted dry.  Many kinds also are now pre-
 pared in this way, as  opaque  objects to be  examined with the
 lieberkuhn,  and are  exquisitely beautiful.  Others, however, are
 almost invariably mounted in balsam ; but as these will  be again
 referred to in Chapter III., and require the same treatment to fit
 them for the  slide,  it will not be out  of place to describe the
 cleaning and preparation of  them  here.  As before stated, there
 is much matter surrounding them which must be  got rid of before
 the " siliceous  covering"  can be shown  perfectly.  As, however,
 we may first wish to become acquainted in some degree with what
 we have to do, it is well to take a small  piece of  talc, and place a
 few of the diatoms upon it.   This may be held over the flame of
 the spirit-lamp until all  the  surrounding matter is burnt away,
 and a tolerable idea may be thus obtained as  to the quality of our
 treasure.
  In  some cases it is well to  use this burning operation alone in
mounting specimens of diatoms,  when they may be placed in their 
                   OF MICROSCOPIC OBJECTS.                35

natural state upon the thin glass, burnt for awhile upon the plati-
num plate, hereafter described, and mounted dry or in balsam.
  In the preparation  and cleaning of Diatomaceae, there is little
satisfaction unless  these operations have been successfully per-
formed, as a very small portion  of  foreign matter seriously inter-
feres with the object.  The mode  of preparing them varies even
amongst the most experienced.   It will be found, therefore, most
satisfactory to examine the principal of these separately,  although
it may be at the risk  of some little  repetition.
  The method which is  the most  frequently made use  of  is  the
following:—Place the "gathering" containing the Diatomaceae in
a small glass or porcelain vessel, add strong nitric acid, and, by the
aid of Bunsen's burner or spirit-lamp,  boil  for some  minutes.
From time to  time a drop of the mixture may be put upon a slide,
and examined under the microscope to  see if all foreign matter be
got rid of.  AVhen the valves are clean,  the vessel containing them
must be filled with water, and the  whole left  for an hour or two,
so that all the diatoms may settle perfectly.  The liquid must then
be poured off  carefully, or drained  away by the aid  of a syphon,
so that none of the diatoms are removed with it.   Indeed, it is
well to examine the liquid drained off  each time with the  micro-
scope, as the finer forms  are frequently lost in the washings.  The
vessel must then be refilled with pure water, allowed to settle, and
drained as before.  This washing must be  repeated until a drop
being placed  upon a slide and evaporated  leaves  no crystals.
When it is desirable  to  preserve the diatoms in this state before
mounting (which process will be described in another place), they
may be placed in a small phial with a little  distilled water.
  There are many cases in which the above method will not effect
a perfect cleansing,  as certain  substances  with which the diatoms
are frequently mixed are not soluble in nitric acid.  For this reason
the following  method is resorted  to:—Take  a quantity  of the
matter containing the Diatomaceae and  wash first with pure water,
to get rid of all the impurities possible.   Allow this to settle per-
fectly and decant  the Avater.   Add hydrochloric acid gradually,
and Avhen all effervescence has subsided, boil for some minutes by
aid of the lamp.   When cool  and the particles have  subsided,
decant the hydrochloric  and add nitric acid.   The  boiling must 
36
PREPARATION AND MOUNTING
then be repeated until a drop of the liquid when placed under the
microscope shows the valves or  " frustules" clean.   After allowing
the diatoms to settle, the acid must be decanted, and pure water
substituted.  The  Avashing must be repeated as in the former pro-
cess until all the remains of crystals or acid are removed, Avhen the
specimens may be preserved in small phials as stated above.
   Such are the usual modes of treating the Diatomaceae, but there
are certain cases in which particular methods are required to give
anything like perfect results.   Persons of great experience com-
bine a variety of treatments, and thus obtain better and more uni-
form specimens.  Perhaps  it will be  advantageous to give  the
young student the process adopted by  one of the most successful
preparers of these objects;  but I will first state the different me-
thods  of  mounting  the  cleaned diatoms  dry:  how to employ
Canada balsam and  fluid  in their preservation will be elsewhere
described.
   It was before stated that the diatoms when cleansed might be
preserved in small  phials of distilled  water. When required for
mounting, shake the phial, and with a  thin glass tube or rod take
up a drop of the fluid and  spread it upon the surface  of the slide
in the  desired position.  This  must then be allowed to dry  gra-
dually,  or by  the  aid of  the  lamp if necessary, without being
shaken or interfered Avith, otherwise uniformity of dispersion  will
be prevented.   When thoroughly dry, a thin ring of one of the
adhesive varnishes—gold-size will be found as good as any—may
be draAvn  round the diatoms, and allowed to dry in a slight degree.
The slide and thin  glass cover should then be  Avarmed and the
latter gently pressed upon the  ring of varnish until the adhesion
all round is complete.
   As some  of the  diatoms require object-glasses  of extremely
high power, and consequently  short  focus, to  show them, they
must  be as  close to  the outer  surface of  the cover  as possible.
For this  reason they are sometimes placed upon the under  side
of the thin glass, as follows.  Clean the surfaces of the slide and
cover, and Avith the rod or pipe  place the liquid containing the
diatoms upon the thin glass, and dry  as before.  Trace the ring
to receive the cover  upon the  slide, and when almost dry, warm
both and proceed as  above.   Whichever  of these  methods  is 
OF MICROSCOPIC OBJECTS.
3V
employed, the  outer  ring of coloured varnish may be applied as
elsewhere described and the slide finished.
  The diatoms are  also sometimes mounted betAvixt tAVO  thin
glasses, as described in  Chapter I., so  that the light  by which
they are examined may receive as little interference as possible,
and  that  an achromatic  condenser may be brought  into focus
under the slide.
  Of the  various  modes  of cleaning and mounting the  Diato-
maceae, I believe that the following may be safely recommended
as affording results of the very best quality.  My friend, Mr. T. G.
Rylands, gave it to me as that which he prefers, and I can safely
say that his numerous slides are at least equal to any I have ever
seen.  I will give it just as I  received it from him, though there
may be some little repetition of what has been said elsewhere, as
he does not appropriate  any part of it as  his own.  He says:
In this branch of mounting,  general  rules  alone  can be laid
down,  because the gatherings may contain iron,  lime, fine silt,
or vegetable  matter  under conditions for special treatment, and
consequently the first step should be to experiment on various
kinds.
  In gathering diatoms much labour is  saved by judgment and
care; hence it  is desirable to  get' acquainted with them in their
growing condition, so that when recognised upon  the sands or
other spots  they may be  carefully removed  by the aid  of the
spoon or small  tin  scoop before  described.   When groAving upon
algae or other plants,.the plants and diatoms together may  be car-
ried home, in Avhich case they must  be simply drained and not
washed or pressed, in order that the diatoms  be not lost.   As it
is ahvays desirable  to examine the gathering on  the ground, a
"Gairdner's  hand microscope" Avith  poAvers  from 80 to  200
diameters will  be  found very useful.  The best gatherings are
those which represent one species abundantly.  Those Avhich are
mixed may be rejected, unless they are seen to contain something
valuable or important, as the  object  should not  be so much to
supply microscopical  curiosities as to collect  material  which is
available for the study of nature.
  The gathering Avhen carried home should always be carefully
examined before anything is  done with it; not only on account 
38
PREPARATION AND MOUNTING
of the additional information thus  acquired, but  also because it
often happens that a specimen  should be  mounted in fluid (see
Chapter IV.) in the condition in which it is gathered,  as well as
cleaned and mounted in balsam  (Chapter III.) and dry.
  Where the gathering is taken from sand, the  whole may be
shaken up in water as a preliminary operation, when much  of the
sand will  be separated by its OAvn  weight.   The lime test, hoAv-
ever,  should be  applied, viz.—a  small portion of hydrochloric
acid, and if there be effervescence  it must  be  dissolved out by
this  means.  From  Algae and  other weeds diatoms  may  be de-
tached by agitating  the whole  together in  a Aveak  solution  of
nitric acid—about one of pure acid  to tAventy or thirty of  water,
as it must be sufficiently weak  to free the diatoms without des-
troying the matter to which they adhere.   The diatoms may then
be separated by sifting through coarse muslin, which will  retain
the  Algae, &c.   The process of cleaning  will vary according  to
circumstances.   Some gatherings  require to be boiled only a few
minutes in nitric acid;  but the  more general plan Avhere they are
mixed with organic or other foreign matter, is to boil them in
pure  sulphuric acid  until they cease to groAV  darker  in  colour
(usually from a half to one minute), and then to add, drop by drop
to avoid  explosions, a cold saturated solution of chlorate of potash
until the  colour is discharged, or, in case the colour does not disap-
pear, the quantity of the solution  used is at least equal to that of
the acid.   This operation is  best performed in a  Avide-mouthed
ordinary beaker glass,* a test-tube being too  narroAV.  The mix-
ture Avhile boiling should be pouied into thirty times its bulk of
cold Avater, and the whole alloAved  to subside.  The fluid must
then  be  carefully decanted  and  the  vessel re-supplied once  or
tAvice with pure water, so as to get  rid of all the acid.   The gather-
ing may  then be transferred to a small boiling glass or  test-tube,
and—the water being carefully  decanted—boiled in  the smallest
available quantity of nitric acid, and Avashed as before.   This last
process has been  found necessary from the  frequent appearance

  * These glasses are round, about six  inches high, and usually  contain
about eight ounces.  They are rather  wider at the bottom, tapering gradually
to the top, aDd may be generally procured at the chemists, &c. 
OF MICROSCOPIC OBJECTS.
39
of minute crystals, which cannot otherwise be readily disposed of
without the loss of a considerable proportion of diatoms.
  I may here  mention that the Avashing glasses used  by Mr.
Rylands are stoppered conical bottles varying in capacity from
tAvo ounces to  one quart; the conical form being employed  to
prevent the adherence of anything to the side; they are " stop-
pered " to render them available in the shaking process about  to
be described.
  The gathering, freed from acid, is now  put into tAvo inches
depth  of  Avater, shaken  vigorously  for  a  minute  or two, and
allowed to subside for half an hour, after  which the turbid fluid
must be  carefully decanted.   This operation must be  repeated
until  all the matter is removed which will not  settle in half  an
hour.  The fluid removed should be examined by  a drop being
put upon  a slide, as in some  cases very light diatoms  have been
found to come off almost pure in one or more of these earlier wash-
ings.   The quantity of water and time of subsidence given may be
taken generally, but may require to be modified according to cir-
cumstances and the judgment of the operator.  By the repetition
and variation of this process—the shaking being the most im-
portant part—the gathering, if a pure one,  will be  sufficiently
clean.   If, hoAvever, it contains a variety of species and  forms, it
may require to be divided into different densities.
   In some cases, however, it is best to divide  the gathering as  a
preliminary operation, which may be done by  agitating it in  a
 quantity of water and decanting Avhat does not  readily  subside.
 The heavier and the lighter portions are then to be treated as tAvo
 separate boilings.  But when  the  cleansing has been carried  to
 the above stage and  this division is  required, the plan  must  be
 somewhat as follows:—The gathering must be shaken in a test-
 tube with six inches of water,  and then allowed  to  subside until
 one inch  at the top remains pure.  About three  inches  are then
 to be carefully withdrawn by a pipette,  when the  tube may  be
 filled up and the operation repeated.  The three lower inches also
 may then be decanted  and examined.  The gathering is thus
 divided into three portions, viz.—that which was withdrawn  by
 the pipette, that which remained floating in the lower three inches
 of Avater in the tube, and that which had settled at the bottom. 
40
PREPARATION AND MOUNTING
An examination of these will inform the  operator  how to obtain
that particular density of gathering Avhich he desires, and how far
it is Avorth Avhile to refine this  process of elutriation ;  for in cases
of necessity any one, or all three, of these densities may be ope-
rated upon in the  same way to separate a particular diatom.
  As occasional aids, it may  be remarked, that  in  some  cases
liquor ammonkc may be used in place of Avater, as it  often  sepa-
rates fine dirt, which is not otherwise easily got  rid of.   Some
fossil deposits require to be treated Avith a boiling solution of car-
bonate of soda to  disintegrate them ; but this  operation requires
great care, lest the alkali should destroy the diatoms.   Vegetable
silicates also sometimes require  to be removed by a solution of
carbonate of soda ; but as the  frustules of the diatoms themselves
are but vegetable silica, even more care  is required in this case.
It may be Avell to  mention, that some diatoms  are  so  imperfectly
siliceous that they will  not  bear boiling  in acid  at all.  Some of
these may  be  alloAved to  stand  in cold nitric  acid  some  time,
Avhilst others of a smaller and more delicate character  should,
Avhen possible, be  treated with distilled water alone.
  We will now consider the mode of  mounting the prepared dia-
toms, Avhich, if used dry (as described in this chapter), should be
carefully Avashed  two  or  three  times with the purest  distilled
water.   In  this branch, as in every  other, each  collector  gives
preference to that method in  which  he  is an  adept.  Thus  the
diatoms may be placed on the under  side of the  cover, to be as
near to the object-glass as  possible, or upon the slide itself; and
each plan has its advocates. Whichsoever of these is used,  no-
thing seems more simple to the novice than a tolerably equal  dis-
persion  of  the objects upon the slide or cover;  but this is by no
means so readily  accomplished, consequently I give Mr. Rylands'
method, as his  slides are perfect in this respect also.   He  always
places the  diatoms upon the thin glass cover.   It is not sufficient,
as is frequently thought, to take  a drop  of liquid  containing  the
cleansed material and  spread it  upon the coATer or slide, as with-
out some additional precaution that uniform and regular distribu-
tion of the specimens is not obtained which is desirable.   In order
to effect this, let a drop of the cleansed gathering be diluted suffi-
ciently  for the purpose—how much must be  determined in each 
OF MICROSCOPIC OBJECTS.
41
case by experiment—and let the covers to be mounted be cleaned
and laid upon the brass plate.   (See Chapter I.)  By means of a
glass tube, about one-twelfth of an inch in diameter, stopped by
the wetted finger at the upper end, take up as much of the diluted
material as will form a moderately convex drop extending over
the Avhole cover.   When all the covers required are thus prepared,
apply a lamp below the brass plate, and raise the temperature to
a point just short of boiling.   By this means the covers will be
dried  in a feAv  minutes, and  the specimens equally distributed
over the whole area.   The  spread of the fluid upon  the  covers is
facilitated by breathing upon  them;  and, to insure uniformhy,
care must be taken to avoid shaking them whilst  drying.   The
best plan is to mount at least half a dozen at once.
  Before mounting, Mr. Rylands always burns the  diatoms upon
the glass at a dull  red heat, Avhether they  are used with balsam or
dry.  This burning, he says,  is  not only  an additional cleaning
process, but it effectually fixes the  diatoms,  and prevents  them
floating out if mounted Avith balsam.  The thinnest covers may be
burnt without damage if they are placed  upon  a small piece of
platinum foil  of the  size required, which should be about one-
hundredth of  an inch thick, perfectly flat, and having three of its
edges  slightly bent over, so as to prevent  its  warping with  the
heat,   The small flame of a spirit-lamp, or, Avhere there  is  gas, a
Bunsen's burner, may be employed.   The cover should be shaded
from direct daylight,  that the  action of the flame may be observed
more perfectly.  Care must  then be taken to raise the tempera-
ture only to the dull red heat  before mentioned.   The cover will
then be in a fit  state for mounting as required.
   It has been stated in another place that it is assumed the opera-
tor is not mounting diatoms simply as microscopic objects, but as
instructive specimens.  It  is  not, therefore,  sufficient to  take  a
single  slide as all that is required, but to have the same diatom
prepared in as  many ways as possible.   The following are  the
principal:—

     1. Mounted crude in fluid (see Chapter IV.).
     2. Burnt crude upon  the cover, and mounted  dry or in bal-
          sam (as  before mentioned).
                              3* 
42
PREPARATION AND MOUNTING
     3. Mounted  dry  or  in  balsam (see  Chapter III.), after the
         cleansing process already described.

  I will here give Mr. Rylands' method  of mounting them dry,
the fluid and balsam preparations being noticed in their  respec-
tive  chapters.  The slide with the ring of asphalt, or black var-
nish, should have been  prepared some weeks previously, in order to
allow it to dry thoroughly.  When required, it must be held over
the spirit-lamp or Bunsen's  burner until the ring of varnish  is
softened.  The burnt cover, having been heated at the same time,
must then be taken in the forceps and pressed upon the softened
varnish until.it adheres all round.   When  cold, an outer ring of
asphalt completes the slide.
  Such is the method Avhich my friend Mr. T. G. Rylands  em-
ploys in the preparation of diatoms for the microscope.   I have
said enough concerning his results.  It is to be feared, however,
that to some these several modes of operation may appear lengthy
and complicated; but if read carefully, and the experiments tried,
they will be found simple enough in practice, and to occupy much
less  time than an intelligible  description would lead the novice to
believe necessary.
   One of the most fertile as Avell as the most curious magazines of
Diatomaceae is guano.  The siliceous forms contained  therein have
been devoured by sea-birds and passed through the stomach unin-
jured,  and  after  lying for  ages may be  cleaned and  classified.
Many  of these are  not elsewhere  met with, so that  the  student
Avho is desirous to enter into the study of Diatomaceae must be in-
structed as to the best mode of obtaining them from this source.
The particulars to be  observed so closely resemble those before
mentioned in the treatment of the ordinary diatoms, that it will
be  sufficiently explicit to give the outlines of the process.  The
guano must be first Avashed in pure Avater, allowed to  subside per-
fectly, and  the liquid  then  poured off.   This must  be-repeated
until the top fluid is clear, and care taken not to decant the liquid
until perfect subsidence has taken place.  The deposit must then
be treated with hydrochloric acid with a  gentle heat for an hour
or tAvo, adding a little  fresh acid at  intervals as long  as it  excites
any effervescence.  After this nitric acid must be substituted for 
OF MICROSCOPIC OBJECTS.
43
the hydrochloric, and the heat kept up to almost boiling-point for
another hour at least, adding a little fresh acid as before.  When
this ceases to act, the deposit must be allowed  to settle perfectly
and the acid poured off.  All traces of  the acid must now be
washed aAvay Avith pure water, when the remains will be Diatoma-
ceae, the sand contained in  the  guano, and a feAV other forms.
Some of these may be mounted dry, as before mentioned, but the
greater portion should be put up  in Canada balsam as described
in Chapter III.
   Such is the ordinary method for the treatment of guano; but
Mr. Rylands' mode of proceeding Avith ordinary Diatomaceae (be-
fore given) Avill be found equally successful Avith these  deposits.
   The  fossil Infusoria (as they  were formerly  called) are now
termed Diatomaceae, and are found in various parts of the world
—"Bermuda  earth," "Berg-mehl" from Norway, deposit from
Mourne Mountain in Ireland, &c.  They are found  in immense
quantities, and afford the microscopist innumerable objects.  The
same treatment as that usually employed for the Diatomaceae must
be followed with these  deposits, but  as they are sometimes ob-
tained in hard masses, disintegration is first necessary.  To effect
this, they are usually boiled for a short time in diluted liquor po-
tassa;,  Avhich will soon cause the mass to fall into a mud-like de-
posit.   Water must  then be immediately added, in order that all
further action of the liquor potassm  may be  stopped, otherwise
the objects searched for will  be  dissolved.   For this  reason it is
necessary to understand Avhat substance is being dealt with, be-
cause some deposits are much finer and acted upon more readily
than, others.
   In mounting these objects, some are so delicate that they are
almost invisible when balsam is used with them; they are  there-
fore usually mounted dry.   Others, however, are much coarser,
and may be mounted in balsam like the Diatomaceae mentioned
in Chapter III.
   The common  Infusoria cannot be mounted dry with any great
success, though a few may be placed upon the glass slide and
allowed to dry naturally, when their characters will be very well
shoAvn.  To obtain anything like a natural appearance, they must
be put up in fluid as in Chapter IV. 
44
PREPARATION AND  MOUNTING
  Next to the Diatomaceae, no class of microscopic objects has
been more looked into of late than  the Foraminifera.   These
animals are almost all marine, having a jelly-like body  enclosed
in one or more chambers of shell generally composed of^arbonate
of lime.  The shells are made Avith minute orifices, through Avhich
the pseudopodia (false feet) are extended by which the animal is
enabled to lay hold of anything and draAV itself along.   From the
possession of these  orifices  they  derive their  name, as foramen
means  a door or opening.   They have been found in every depth
of sea hitherto  sounded, each depth  being  abundant in certain
species;  the loAvest  beds  containing the  greatest number  of
specimens, though  with  less  variation  of  kinds.   In  chalk
they are found in a  fossil  state, and may readily be shown (see
Chapter III.);  in  limestone  and  other hard  stones they  are
abundant, and some  mountains are composed principally of these
shells.
  The methods of obtaining Foraminifera are various.  Many may
be  found  upon  seaAveeds, which  should always be examined as
soon as possible after gathering.   They are found in masses upon
some coasts  Avhere the waves have carried and left them ;  but
they are to be found the most abundantly in  sand or mud dredged
from the bottom of the sea.  They must, however, be cleansed and
separated from the mass of impurity with Avhich they are usually
mixed.   This may  be done in various  ways, according to  the
nature of the accompanying matter.  If sand alone,  as is frequent-
ly the  case,  the Avhole mass must be thoroughly dried,  and then
stirred up in clean Avater.   The sand will soon subside by its own
weight, but the chambers of the Foraminifera,  being filled .with
air, Avill float upon the  surface, and may be  skimmed off.  There
is,  hoAvever, one objection to this mode of proceeding—some of
these objects are so  minute, the  chambers containing  compara-
tively so small a quantity  of air, that they sink and are cast away
Avith the refuse sand.   On this account it is preferable to take the
trouble of searching certain soundings under the microscope, using
the camel-hair pencil, or some other contriAance before mentioned,
to  extract those objects which  are required.   To clean  the Fora-
minifera,  Professor Williamson advises to transfer  the specimens
to an evaporating dish containing a weak solution of caustic potash. 
OF MICROSCOPIC OEJECTS. .
45
This must be  boiled for "some  moments," when the  organic
matter will be entirely dissolved,  and the calcareous  shells left
free from impurity.  They must now be well washed in Avater,  so
that all alkaline matter may be entirely got rid of.
  If the specimens are in mud, we must proceed in a different
way:—Stir up the Avhole mass in water, and  allow  it to  stand
until the heavier portion has sunk to the bottom; the water may
then be poured off and examined to see  if there are any objects
contained in it.  This process must be repeated  until the  water
comes off quite clear, when (if the search is for Foraminifera only)
the solution of caustic potash may be used as before  mentioned.
However the soundings, &c, are cleaned, it is necessary to  assort
them under the microscope with the camel-hair  pencil or  other
contrivance, as it is impossible  to obtain them fit for mounting
without undergoing this process.
   The sea soundings taken by order of Government  are  drawTi
from the bottom in a kind of apparatus ingeniously made for the
purpose, and the sand, mud, &c, are brought up in their original
state.   Common  soundings, hoAvever, are taken by  loAvering a
heavy piece of lead coated Avith tallow, which consequently  brings
up a small portion of the matter from the bottom.   Mr. George
Mosley, the late Secretary of the Manchester Microscopic Society,
obtained numbers of the " scrapings" from the  sounding  leads.
To make any use  of these it is, of course, necessary to free them
from all traces of  the tallow.   Mr. Dancer places the sounding in
a basin and pours boiling water upon it, Avhich causes the melted
grease to rise to the  surface.   When cold, this may be removed,
and the water carefully decanted.  The operation may be repeated
until no grease appears, Avhen the water may be withdrawn  and
liquor ammonice  used, which will form a soapy solution with any
remaining grease.  This must be treated with hot water for  the
 final washing.  Care must be taken lest  the finer forms be carried
 away in decanting the  washing liquid.   Should it be wished to
 make certain as to this point,  each Avashing should be examined
 under the microscope.   In  some cases the process of Mr. Dancer
 will prove sufficient.  Mr. Dale, however, gives a method of accom-
 plishing the same result, which is much more readily completed;
 and as the results cannot be found fault with, I will here  give it 
46
PREPARATION AND MOUNTING
 in full:—It is now Avell knoAvn that one of the products obtained
 from the naphtha of coal-tar is a volatile, oily substance, termed
 benzole (or,  by French chemists,  benzine),  Avhose  boiling-point,
 when pure, is about 180° Fahrenheit, Avhich is a perfect solvent for
 fatty substances.   In a  capsule, preAaously Avarmed on a sand-bath,
 Mr. Dale mixes Avith the tallow soundings benzole, whose boiling-
 point  may be  about 200°, until sufficiently diluted so as to run
 freely,  pressing  the lumps with  a  glass  rod until thoroughly
 mingled; the solution  and its  contents  are then poured into a
 paper  filter,  placed in a glass funnel; the capsule is again Avashed
 with benzole, until the Avhole of the gritty particles are  removed
 into the filter.  A washing-bottle  is then supplied Avith benzole,
 and the contents  of the  filter washed to the bottom until  that
 liquid passes off pure,  AArhich  may be tested  by placing a drop
 from the point of the  funnel on a Avarm slip of glass  or bright
 platinum, when, if pure, the benzole will evaporate  Avithout  resi-
 due or tarnish ; if grease be present, the washings must be  con-
 tinued  until  they are free from it.   After  rinsing through  weak
 acid, or alcohol, for final purification, the calcareous forms will be
 ready for mounting.
   The  filter  and its contents may be left  to dry  spontaneously,
 when  the latter can be  examined by the microscope.  Should
 time be  an  object, rapid drying may be effected by any of the
 usual methods; one of  which, recommended by Mr. Dale,  is to
 blow a  stream  of hot air through a glass tube held  in the flame
 of a Bunsen's burner.  The lower the boiling-point of the benzole,
 the more readily  can the  specimens be freed  from  it.   A com-
 moner quality  may be  used, but it is more difficult to dry after-
 wards.
  Pure benzole  being costly, this may appear an expensive pro-
 cess ; but, Avith the exception of a trifling loss by evaporation, the
 AArhole may be recovered by simple distillation.   The mixture of
 tallow'and benzole being placed in a retort in a hot-Avater, a steam,
 or a sand bath,  the benzole will pass into  the receiver,  and  the
tallow  or other impurities  Avill remain in the retort.  When  the
whole of the  benzole has distilled over,  which is ascertained by
its ceasing to drop from the condenser, the heat is withdraAvn  and
the retort allowed to cool before the addition of fresh  material. 
OF MICROSCOPIC OBJECTS.                47
Half a dozen to a dozen filters, each with its specimen, can be in
process at  the  same time;  and the distillation of the  recovered
benzole progresses as quickly as the filtration,  which Avas practi-
cally proved on the occasion named.   Great caution in the use of
benzole is  to be taken in the approach of lights to the inflamma-
ble vapour.
   After the Foraminifera and calcareous forms have been removed,
the residue may be treated Avith acids and levigation in the usual
manner,  to obtain siliceous  forms and  discs,  if  there  are any
present; but to facilitate their  deposition,  and to avoid the loss
of any minute atoms suspended in the washings, I would suggest
the use of filtration.  The conical  filter is unsuitable, as the  parti-
cles would spread over too great a surface of paper;  but glass
tubes open at both ends (such as broken test-tubes) will be found
to answer,  the  broad end covered with  filtering paper, and over
that a slip of muslin tied on with a thread to facilitate the passage
of the water and prevent the risk of breaking the paper.   Suspend
the tube over a suitable vessel through a hole cut in thin Avood or
cardboard,  pour in the washings,  Avhich can be thus filtered and
then dried.  The  cloth must be carefully removed, the  paper  cut
round  the  edges of the tube, and  the  diatoms  on the paper disc
may be removed by a  camel-hair  pencil or. otherwise, ready  for
mounting.   Thus  many objects may be preserved which Avould
be  either Avashed  away or only be obtained by a more tedious
process.
   Such is  Mr. Dale's method of cleaning the soundings from  the
tallow,  and as it  thoroughly accomplishes  its  end, and is  alike
effective and not injurious to Foraminifera and diatoms, it may be
safely recommended.   The Aveak solution of caustic potash before
advised for Foraminifera, must  not be used  Avhere it is desired to
preserve the diatoms, as they would certainly  be injured,  or  de-
stroyed altogether, if this agent were employed.
   In fixing the  Foraminifera upon the slide,  no  better plan can be
folloAved than the " dry cells" and  gum recommended in the  early
parts of this chapter.   Owing to their thickness and composition,
most of them are opaque objects only ; but they  are exquisitely
beautiful, and require no particular care, except in allowing the
cell, &c, to be perfectly dry, when the cover is placed upon it, or 
48               PREPARATION AND MOUNTING

the damp will certainly become condensed upon  the inner side,
and the examination seriously interfered Avith.
  Many of the Foraminifera require  cutting into  sections if it is
Avished to examine the internal structure, &c,—" decalcifying" is
also  desirable in some cases;—both  of these processes will be
found described at length in the chapter on Sections and Dissec-
tion.
  When more  than one specimen of some particular shell  is ob-
tained, it is better to place them upon the slide in different posi-
tions, so as to show as much of the structure as possible.   I will
conclude  this  subject by  quoting a passage  from T. Rymer
Jones:—" It is, therefore, by no means  sufficient to treat  these
shells as ordinary  objects by simply laying them on a glass slide,
so as to see them only from one or two points of ATieAv; they must
be carefully examined in every direction, for  such is the diversity
of form that nothing short of this will be at all satisfactory.  For
this  purpose, they should be attached to the point of a fine needle,
so that they may be turned in any direction, and examined by
reflected light  condensed upon them by means of a lens or side
reflector.   In many of the  thick-shelled species it Avill be neces-
sary to grind them  down on  a hone  [see Chapter V.] before  the
number and arrangement of the internal chambers is discernible;
and  in  order to investigate  satisfactorily the minutiae of their
structure, a variety of sections, made in various Avays, is indispen-
sable."
   Plants  afford an almost inexhaustible treasury for the micro-
scope, and many of them show their beauties best when mounted
dry.  When any of these also are  to be mounted,  care must be
taken that they are thoroughly dry, otherAvise the damp will cer-
tainly arise in the cell, and injure the object; and it may be here
mentioned that long after a leaf has every  appearance of dryness,
the  interior is still  damp, and no  Avay can be recommended of
getting rid of this by any quicker process than  that effected by
keeping them in a warm room, as many leaves, <fcc, are utterly
spoiled by using a hot iron  or other contriA^ance.   The safest way
is to press them gently betAvixt  blotting-paper,  which may be
removed and dried at short intervals ;  and though this may appear
a tedious  operation, it is a safe one. 
OF MICROSCOPIC OBJECTS.
49
  On the surface of the leaves, hairs and scales of various  and
very beautiful forms are found, most of Avhich display their beau-
tics best when removed from the leaf, and used Avith the polarizer.
These will be noticed in another place; but a portion of the leaf
should always be prepared in its natural form, to shoAv the arrange-
ment of the hair or scales upon it; which must almost invariably
be  mounted dry  when used for  this purpose.  Many  of them
require very delicate handling.  The epidermis, or, as it is by some
termed, the cuticle, is  the  outer skin which lies upon the surface
of the leaves  and other parts of most plants.   This is composed
of cells closely connected, often bearing the appearance of a rude
network.   In many plants, by scraping up the surface of the  leaf,
a thin coating is detached, Avhich may be torn off  by taking hold
of it with the forceps.  The piece may then be washed and floated
upon a glass slide, Avhere, on drying, it will  be firmly fixed,  and
may usually be  mounted  dry. Amongst the most  beautiful and
easily prepared  of these may be mentioned the petal of the gera-
nium, the cells  of Avhich are well  defined and amongst the most
interesting.
   Closely connected Avith the leaves are the anthers and  pollen,
of Avhich a great number are beautiful and interesting subjects for
the microscopist.
   The  malloAV tribe will furnish  some exquisite objects,  bearing
the  appearance of masses  of costly jewels.    These are usually
dried Avith pressure, but the natural form may be more accurately
preserved by allowing them  to  dry as they  are taken from  the
floAver,  Avith no interference except thoroughly protecting them
from all dust.   Sometimes  the anther is divided,  so that the cell
required  to  receive them may be of as little depth as possible.
The common mallow is a beautiful object, but I think the laA^atera
is a better,  as it shoAvs the pollen  chambers well, Avhen dried im-
pressed.  The pollen  is often set alone,  and is  well worth the
trouble, as it then admits of more close examination.  Often it is
convenient to have the anther and pollen as seen in nature on one
slide, and the pollen alone upon another.  The former  should be
taken from the  flowers before their full development is attained,
as if overgrown they  lose much of their beauty.   Some pollens
are naturally so dark that it is necessary to mount  them in Canada 
50
PREPARATION AND  MOUNTING
balsam or fluid, as described in other places ; but they are better
mounted dry Avhen they are not too opaque.
  Here,  too, Ave may also mention the seeds of many  plants as
most interesting, and some of them very beautiful, objects, requir-
ing for the greater part but a Ioav poAver to show them.  Most of
these are to be mounted dry, as opaque objects, in cells suited,.to
them, but some are best  seen in balsam,  and will be mentioned
in Chapter III.
  The Corallines, many of  Avhich are found on  almost every
coast, afford some very valuable objects for the microscope.   They
must be Avell washed Avhen first procured, to get rid of all the salts
in the sea-Avater, dried and mounted in cells deep enough  to pro-
tect them from all danger  of pressure, as some of them are exceed-
ingly  fragile.   The white ivory appearance which some of them
present is given to them by an  even covering of carbonate of lime;
and should  it be desired to examine the structure of these more
closely, it may be accomplished by keeping them for some time
in vinegar or dilute muriatic acid, Avhich Avill remove the lime and
alloAV of the substance being sliced in the same Avay as other Algae.
("Micrographic Dictionary," p. 183.)
  The Scales of Insects.—The fine dust upon the  Avings of
moths  and  butterflies, which  is readily removed when handled
carelessly, is what is generally called scales.  To these  the Aving
oavcs the magnificent colours  Avhich so often are seen  upon  it;
every particle being  Avhat may be termed a distinct flat feather.
Hoav these  are placed (someAvhat like tiles upon a roof) may be
easily seen in the Aving of any  butterfly, a feAV being removed to
aid the investigation.  The form of them is usually that of the
" battledore" Avith Avhich the  common game is played, but the
handle or base of the scale is often short, and the broad part varies
in proportionate length and breadth  in different specimens.  The
markings upon these  also vary,  some being mostly composed of
lines running  from the base to the apex, others reminding us of
network—bead-like spots  only are seen in some—indeed,  almost
endless changes are found amongst them.  These scales are not
confined to butterflies and moths, nor indeed to the wings of insects.
The different  gnats supply  some most beautiful specimens,  not
only from the  Avings, but also from  the  proboscis,  &c.; Avhilst 
OF MICROSCOPIC OBJECTS.                51
from still more minute insects, as the podura, scales are taken
Avhich Avere at x»ne time esteemed as a most  delicate  test.   The
gorgeous colours which the diamond beetles also shoAV when under
the microscope are produced by light reflected from minute scales
Avith which the insects are covered.
  In mounting these  objects for the microscope it is well to have
the part of the insect from  which the scales are usually taken as
a separate slide, so that the natural arrangement of them may be
seen.  This is easily  accomplished with the  wings of  butterflies,
gnats,  &c.; as they require no extraordinary  care.   In mounting
the  scales they may be placed upon slides, by passing the wings
over the surface, or by  gently scraping  the wing  upon the slide,
Avhen they must be covered Avith the thin glass.  Of course,  the
extreme tenuity of these objects does aAvay Avith the necessity of
any  cell excepting that formed by  the gold-size or other cement
used to attach the cover.   The scales  of the podura  should be
placed upon the slide in a somewhat different manner.   This insect
is without wings, and is no longer than  the common  flea.   It is
often found amongst the saAvdust in Avine-cellars, continually leap-
ing about by the aid of its tail, which is bent underneath  its body.
Dr.  Carpenter says :—" Podurae may be  obtained by sprinkling a
little oat-meal on a piece of black paper near their  haunts; and
after leaving  it there  for a feAV hours, removing it carefully to a
large glazed basin, so that,  Avhen they leap from the paper (as
they Avill AArhen brought to the light), they may fall into the basin,
and  may thus separate themselves from the meal.   The best Avay
of obtaining their  scales, is to .confine  several of them together be-
neath a Avine glass inverted upon a piece of fine smooth paper;
for  the scales Avill become detached by their leaps against  the
glass, and will fall upon the paper."  These scales are  removed
to the slide, and mounted  as those from the gnats, &c.  When
the podura has been  caught Avithout the aid of the meal, it may
be placed upon the slide, under a test-tube, or by any other mode
of confinement,  and  thus  save the trouble of transfer from  the
paper  before mentioned.   Another method is to serze the insect
by the leg with the forceps and drag it across the slide, AA'hen a
sufficient quantity  of scales will probably be left upon it.
  These scales are usually mounted "dry;" but Hogg recom- 
52
PREPARATION AND  MOUNTING
mends the use of Canada balsam (Chapter III.) as rendering their
structure  more definite Avhen illuminated with Wenham's para-
bolic reflector.  Some advise other methods, which Avill be men-
tioned in Chapter IV.  As most insects Avhen  undissected  are
mounted  in  Canada balsam, the  different  modes  of treatment
which they require will be stated in another place.
   In mounting  blood of any kind to show  the corpuscles, or, as
they are often called, globules, Avhich are round or oval discs, it is
but necessary to cover the slide on the spot required with a coat-
ing as thin as possible and  alloAv it to dry  before covering Avith
the thin glass.   There is a slight contraction in the globules Avhen
dried, but not enough to injure them for the  microscope.   The
shape of these varies in different classes of animals, but the size
varies much  more, some being many times as large as others.—
Some of the  larva? skins are beautiful objects ; but, like many sec-
tions of animal  and other fragile  matter, are  difficult to extend
upon the  slide.  This difficulty is easily overcome by floating the
thin object in clear Avater, immersing the slide and when the ob-
ject is evenly spread gently lifting it.   Allow it then  to dry by
slightly raising one end of the slide to aid the drainage, and cover
with the thin glass as  other objects.   The tails  and fins of many
small fish  may be mounted in a similar manner, and are Avell Avorth
the trouble.
   A few  objects which are best sliOAvn by mounting dry may be
here mentioned as a slight guide to the beginner, though some of
them have been before noticed;—many of the  Foraminifera as
elsewhere described.   Some crystals are soluble in almost any
fluid  or balsam, and should be mounted dry; a feAv, hoAvever,
deliquesce or effloresce, which renders them worthless as  micro-
scopic objects.
   The Avings of butterflies  and gnats,  as before noticed,  afford
many specimens Avherewith to supply the cabinet of  the  young
student.   A  great variety also may be found amongst the  ferns;
indeed, these alone will afford the  student occupation  for  a long
time.  On the under-side of the leaves  are the  reservoirs for the
" spores," Avhich in many instances somewhat resemble green vel-
vet,  and are  arranged in stripes, round masses, and  other  forms.
The  spores are usually covered Avith a thin skin termed the indu- 
OF MICROSCOPIC OBJECTS.
53
sium, which is curiously marked in some  specimens,  often very
like  pollen-grains.  The manner in which these spores with all
their accompaniments are arranged, their changes and develop-
ments afford almost endless subjects for study;  different ferns pre-
senting us with many variations in this respect totally invisible
without the aid of a microscope.  The hymenophyllums (of Avhich
tAvo  only belong to England) are particularly  interesting, and the
structure of the leaves when dried  makes them beautiful objects,
often requiring no balsam to aid their transparency.  Portions of
the fronds of ferns should  be  mounted as opaque objects, after
having  been dried betAveen blotting paper,  when they are  not
injured by pressure; but care must be  taken to gather them at
the right  time, as they do not show their  beauty before they are
ripe, and if over-ripe the arrangement of the spores, &c, is altered.
The spores may be mounted as separate objects in the same man-
ner  as  pollen, before-mentioned,  and are exquisitely  beautiful
when vieAved Avith a tolerably high power.  The number of foreign
ferns now  cultivated in this country has greatly widened the field
for research  in this direction ;  and it may  also be mentioned that
the  under-sides of many are found to be covered with " scales" of
very beautiful forms.  A small piece of the frond of one of these
may be mounted in  its natural state,  but the removal of the
" scales" for examination by polarized light will be  described in
another place.  The mosses also are quite  a little Avorld, requiring
but a low power to show their beauties.  The leaves are of various
forms, some of Avhich resemble beautiful net-AVork; the " urns" or
reservoirs for the spores, however,  are perhaps the most interest-
 ing parts  of these objects, as also of the " liverAvorts" Avhich are
 closely allied to the mosses.  These " urns" are generally covered
by lids, Avhich fall off when the fruit is ripe.  At this period they
 are  well fitted for the microscope.   The common screAv-moss may
 be found in great abundance,  and shows  this denudation  of the
 spores very perfectly.   Many of these may be easily dried without
 much injury,  but they should also be examined in their natural
 state.
   The student should not omit from his cabinet a leaf of the net-
 tle  and the allied foreign species, the mystery of which the micro-
 scope Avill make plain.  The hairs or stings may also be removed, 
54
PREPARATION AND MOUNTING
 and vieAved with a higher power than when on the leaf, being so
 transparent as to require no balsam or other preservative.
   There are few more interesting objects than  the raphides or
 plant-crystals.   These are far from being rare, but in some plants
 they are very minute, and consequently require care in the mount-
 ing, as Avell as a high magnifying power to render them  visible;
 in others they are so large that  about tAventy-five of them placed
 point to point Avould reach one inch.   Some  of these crystals are
 long and comparatively very  thin,  which suggested the  name
 (raphis,  a  needle);  others are  star-like,  with long and  slender
 rays;  while others again are of a someAvhat similar form, each ray
 being  solid and short.  If the stem of rhubarb, or almost  any of
 the  hyacinth  tribe, be bruised, so  that the "juice" may  flow
 upon the slide, in all  probability some of these  crystals  will be
 found  in the fluid.  To  obtain  them clean,  they must be freed
 from all vegetable matter by  maceration.  After this they must
 be thoroughly Avashed and mounted " dry."   They are also good
polarizing  objects,  giving  brilliant colours;  but Avhen used for
 this purpose they must be mounted as described in Chapter III.
 A few  plants which contain them may be mentioned here.   The
 Cactaceae are very prolific; the orchids, geraniums, tulips, and the
 outer coating of the onion, furnish the more unusual forms.
   The Fungi are generally looked upon as a very difficult class of
 objects to deal Avith, but amongst them some of  the most availa-
 ble may be found.  The forms of many are very beautiful, but are
 so minute as to require a high magnifying poAver to show them.
 The mould which forms on many substances is a fungus, and in
 some cases may be dried and preserved  in its natural state.  A
 friend  of mine brought me  a rose-bush completely covered with a
 white blight.  This  was  found to be a fungus, which required a
 high magnifying power to show it.   Being a very interesting ob-
ject, it Avas desirable to preserve it, and this was perfectly effected
 without injury to the form by simply drying the leaf in a room
usually occupied.   Amongst  the fungi  are  many  objects  well
worth  looking  for,  one of which is the  Diachcea elegans.   This,
the only  species, says the " Micrographic Dictionary," is found in
England upon the living leaves of the lily-of-the-valley, &c.   These
little plants grow in masses, reminding one of mould, to a height 
OF MICROSCOPIC OBJECTS.
55
of a  quarter  of an inch,  and each  "stem" is covered with  a
sheath, in shape somewhat like an elongated thimble.  When ripe,
the sheath falls off and reveals the same shaped column, made up
of beautifully fine net-Avork, Avith the  spores lying here and there.
This  dries Avell, and  is a  good object for the middle poAvers.
Amongst the  fungi the blights  of wheat and of other  articles of
food  may be included.   Many of them may be mounted " dry;"
others, hoAvever, cannot be  well preserved except in liquids, and
will be referred to in Chapter IV.  Amongst the zoophytes and
sea-mats, commonly called " sea-Aveeds," may be found many very
interesting objects to be mounted " dry."  When this mode  of
preservation is  used,  it  is necessary that all the sea-salt be
thoroughly Avashed from them.   As they  are, hoAvever, most fre.
quently  mounted in  balsam or liquid,  they will be more fully
noticed in other places.
   The scales of fishes are generally mounted " dry " when used as
ordinary objects; but for polarized  light, balsam or liquid must
be used, as noticed in Chapter  III.   The variety and  beauty  of
these are quite surprising to the novice.  It is also very interest-
ing to procure the skin of  the fish Avhen  possible, and mount it
on a separate  slide to shoAv hoAv  the scales are arranged.   The
sole is one of  the most unusual forms, the projecting end of each
scale  being covered Avith spines, Avhich radiate from a common
centre, while  those  at  the  extremity are  carried out  someAvhat
resembling the rays of a star.  One of the skates has a  spine pro-
jecting from the  centre of each scale,  which  is a very curious
opaque object, especially AA'hen the skin is mounted in the manner
described.   The perch, roach, minnoAv, and others of the common
fishes give the  student good objects for his cabinet, and may be
procured Avithout difficulty.
   Insects Avhich are very transparent, orhaArethe " metallic lustre"
Avith  AA-hich any medium would interfere, are  mounted " dry."
The diamond-beetle, before mentioned,  is a splendid example of
this;  the back is generally used, but the legs, showing the curious
feet, are very interesting objects.  Indeed, amongst the legs and
feet of insects there is a Avidc field of interest.   When  they are
of a  " horny " nature,  it is best to dry them in any form prefer-
red, but to use no pressure; AA'hen, hoAvever,  they are Avanted flat, 
56
PREPARATION AND MOUNTING
so as to shoAv  the feet, «fcc, extended, they must be dried Avith a
gentle  pressure betAvixt blotting-paper if possible.   But this Avill
be treated more fully in Chapter III.
  The eyes of insects are sometimes allowed to dry in their natural
shape,  and mounted as opaque objects; but generally they are
used as transparencies in  balsam or  liquid,  so  the  description of
the treatment  Avhich they  require Avill be deferred to Chapter III.
  Hairs, when not too dark, are  sometimes transparent  enough
Avhen mounted dry,  but are  usually  mounted in balsam.   These
also Avill be more fully  noticed in another place.
  These are a few of the objects Avhich are often mounted dry, but
some of them  should be shown in balsam or liquid also, and there
is much difference  of  opinion as  to the best  way of preserving
others.  This, however, is explained by the transparency which
the balsam gives interfering  Avith  one property of the object and
yet developing another which  would have  remained invisible  if
preserved dry.  The only  method  of overcoming this difficulty is
to keep the object mounted in both ways, which is comparatively
little trouble.
   I may here mention that  many prefer the lieberkuhn for the
illumination of opaque  objects ; and a good back-ground is gained
by putting upon the under side of the slide, immediately beneath
the object,  a  spot  of  black A'arnish, which does  not interfere
materially Avith the  light. 
OF MICROSCOPIC OBJECTS.
57
                    CHAPTER  III.

                MOUNTING  IN  CANADA  BALSAM.

The nature and use of this substance has been before spoken of,
so the method of Avorking with it may be at once described.
   Perfect dryness of the objects is, if possible, more necessary in
this mode of mounting than any other, as dampness remaining in
the object will assuredly cause a cloudiness to make its appear-
ance in a short time after it is fixed.  AVhere pressure does not
injure the specimens, they are most successfully treated when first
dried betwixt the leaves of a book, or in any other Avay which may
prove most convenient, as noticed in Chapter II.
   Before describing the methods of proceeding with any particu-
lar objects, general rules may be given which  should be observed
in order to succeed in  this branch of mounting.
   As the object is to be thoroughly immersed in the  balsam, it is
evident that Avhen it  has once been covered,  so it must remain,
unless we again free it by a  process hereafter mentioned, which is
very  troublesome; and  on  this  account there  must be nothing
whatever in  the  balsam except the object.   The inexperienced
may think this an unnecessary caution ;  but the greatest difficulty
he will meet with is to get rid of minute bubbles of air, perhaps
invisible to the naked eye, which appear  like small globules when
under the microscope, and  render the  slide  unsightly,  or even
worthless.  Ten objects  out of eleven contain air, or at least are
full of minute holes Avhich are necessarily filled  with it;  so that
if they should be  immersed in any liquid of thick consistency,
these cells of air would be imprisoned, and become bubbles.  The
air, then, must be got rid of, and this is usually accomplished by
soaking for some  time  in turpentine, the  period required differing
according to  the nature of the object.  In some cases, the turpen-
tine acts upon the colour, or even removes it altogether, so that it 
58
PREPARATION AND MOUNTING
must be watched carefully.  Often, however, this is an adA-antage,
as Avhere the structure alone is wanted, the removal of the colour-
ing matter renders it more transparent.   There are objects, Iioaa'-
ever,  Avhich retain  the  air Avith such tenacity that soaking alone
will not remove it.   If  these will bear heat Avithout being injured,
they may be boiled in turpentine, or even in balsam, when the air
Avill be partly or totally expelled.  But Avhere heat is objection-
able, they must  be  immersed in the turpentine, and so submitted
to the action of the air-pump.  Even Avith this  aid, sometimes
days  are required to accomplish it perfectly, during  Avhich time
the air should be exhausted at intervals of five or six hours, if con-
venient, and the objects turned over now and then.
   Sometimes the objects are so minute that it is impossible to sub-
mit them to any soaking, and in this case they must be laid upon
the slide at once, and the turpentine applied to them there.   But
it must not be forgotten that there are some feAv which are much
better mounted in  such a way that the balsam may thoroughly
surround, and yet not penetrate, the substance more than necessary.
Sections of teeth are amongst these, which will be  noticed  in
another place, and some insects (see Dr. Carpenter) when required
to shoAv the " ramifications of the tracheae."
   Having freed  the object, then, from these tAvo enemies—damp-
ness and air—Ave must proceed to mount it.
   The slide must first be  cleaned;  then  on  the centre a quantity
of balsam must be placed Avith a bluntly-pointed glass rod, accord-
ing to the size  of  the  object about to  be  mounted.   To this a
slight heat must be applied, which will cause any bubbles to rise
from the surface of the  slide, so that they may be readily removed
Avith a needle.   The object should be freed  from all air by steep-
ing in turpentine, as before described, and then from superfluous
liquid by a short drainage, and carefully  laid upon, or  Avhere it is
practicable thrust into, the  balsam, prepared on the slide as above.
In the former  case, or where the  balsam has not totally  covered
the object, a small quantity must be taken, Avarmcd, and dropped
upon  it, and any bubbles  removed by the needle as before.   To
cover this, the thin glass must be warmed,  and beginning at one
side, allowed to fall upon the balsam, driving a small  " Avave" be-
fore it, and thus expelling any bubbles Avhich may remain.  This 
OF MICROSCOPIC OBJECTS.
59
is quite as safely performed (if not more so) by making a solution
of balsam in turpentine of the consistency of thick varnish.  The
thin glass cover may be slightly coated with this, and will then be
much  less liable to imprison any air, Avhich frequently happens
Avhen  the  cover is dry.   Bubbles, however, will sometimes make
their appearance in spite of all care ; but when the object  is com-
paratively strong, they may be  removed by keeping the slide  ra-
ther Avarm, and working the cover a little, so as to press them to
one side,  Avhen they should be immediately removed Avith a needle
point,  otherwise they are again drcuvn under.
   Where the slide requires keeping Avarm  for any length of time,
a  hot-water bath is sometimes made use of, Avhich is simply a flat
tin, or other  metal case, with a mouth at the side, that when the
hot  Avater is  introduced  it may be closed up, and so retain  its
Avarmth for a long time.  In  Avorking, the slide is laid upon it,
and so admits of longer operations, Avhen required, Avithout grow-
ing cold.   Sometimes a spirit-lamp is placed under it  to keep  up
an  equal  heat through excessively long  processes.  Where  the
time required, however, is but short, a thick brass plate is some-
times used (see  Chapter I.),  Avhich is heated to any degree that
is required, and the slide placed upon it.
   Some  objects, which are so thin that  they are usually  floated
upon the slide, as before stated, require no steeping in turpentine
or other liquid.   These are best mounted  by covering Avith a lit-
tle diluted balsam, and after  this has  had time to penetrate the
substance, ordinary balsam is laid upon it, and the slide finished
in the  usual manner.
   I have stated that the balsam is usually applied to the slide and
objects Avith a " bluntly-pointed glass rod;" but for the purpose of
drawing the balsam from the bottle, and conveying it to the de-
sired place, Dr. Carpenter uses a glass syringe with a free opening.
These  are  his instructions :—" This (the syringe) is most  readily
filled Avith balsam, in  the  first instance, by draAving out the pis-
ton, and  pouring in balsam previously rendered more liquid  by
gentb  Avarmth; and nothing else is required to enable the opera-
tor at  any time to expel precisely the amount of balsam he may
require, than  to Avarm the point of the  syringe, if the  balsam
should have hardened in it, and to apply a very gentle heat to the 
60               PREPARATION AND MOUNTING

syringe generally, if the piston should not then be readily pressed
doAvn.   When  a number of balsam objects are being mounted at
one time, the advantage  of  this plan in regard to  facility and
cleanliness (no superfluous balsam  being deposited on the  slide)
will make itself  sensibly felt,"
  When  the  "mounting"  is thus far accomplished,  the  outer
" wall" of balsam may be  roughly removed after a few hours have
elapsed;  but great care is necessary lest the cover be moved or
interfered Avith in  any Avay.   In  this state it may be left for the
final cleansing  until the balsam becomes hard, which takes place
sooner or later, according to  the degree of warmth it has been
subjected to.  A mantel-piece, or some place about equal to it in
temperature, is  the best suited to this purpose; and  Avhen  the
requisite hardness is attained, it may be proceeded with as follows:
—With a pointed knife the balsam must be scraped away, taking
care that the thin glass be not cracked by the point getting under
it.  If used carefully, the  knife will render the slide almost clean;
but any minute portions Avhich still  adhere to the glass must be
rubbed with linen dipped in turpentine or spirit.   If the balsam
is not  very hard, these small fragments are readily  removed by
folding apiece of paper tightly in a triangular form Avithmany folds,
and  damping the  point with  which the glass is rubbed.  As  the
paper  becomes worn with the friction, the balsam will be carried
off Avith  it.   In some  cases I  have found this simple expedient
very useful.
  Sometimes  the  object to be mounted is of such a  thickness as
to require a cell.   For this  purpose glass rings  are used (as  de-
scribed in Chapter IV.), and filled with balsam.   The best-  mode
of doing this is  thus described by Mr. T. S.  Ralph in the Micro-
scopic  Journal:—" The question was asked me  when I was in
England,  if I knew hoAV  to  fill  a  cell  with  Canada balsam and
leave behind no air-bubbles ?   I replied in the negative; but now
I can state how  to accomplish this.   Fill the  cell  with clear spirit
of turpentine, place the specimen in it, have ready some balsam
just fluid enough to flow  out  of  the bottle when warmed by  the
hand;  pour this on the object at one end, and, gradually inclin-
ing the slide, allow the spirit of turpentine to flow out on  the
opposite  side of the cell till it is full of balsam; then take up the 
OF MICROSCOPIC OBJECTS.
61
cover, and carefully place upon it a small streak of Canada balsam
from one end to the  other.  This, if laid on the cell with one
edge first, and then gradually loAvered until it lies flat, will drive
all the air before it, and prevent any bubbles from being included
in the cell.   It  can be  easily put on* so neatly as to require no
cleaning AA-hen dry.   If the cover is pressed down too rapidly, the
balsam will flow over it, and require to be cleaned off when hard-
ened, for it  cannot be  done safely while fluid at the edges."
  Sometimes with  every care bubbles are enclosed in the balsam
injuring  objects  which  are perhaps rare and valuable.   The whole
slide must then be immersed in turpentine  until the cover  is
removed by the  solution of the balsam;  and the object must  be
cleansed by a similar  steeping.  It may then be remounted as if
new in the manner  before described.
  The balsam and chloroform described in Chapter I. is thus used ;
and Avhere the object  is thin, the mounting is very easily accom-
plished.  When the object is laid upon the slide with a piece of
glass  upon it, and  the balsam and chloroform placed at the edge
of the cover, the mixture  will gradually flow into the space be-
twixt the glasses until  the object is surrounded by it,  and the un-
occupied portion filled.  The  chloroform will evaporate so quickly
that the outer edge Avill become hard in a very  short time, when
it may be cleaned in the ordinary way.   Sometimes the balsam is
dissolved in the chloroform  Avithout being first hardened; but
this is only to render  it more fluid, and so give the operator less
chance of leaving bubbles in the finished slide, as the thicker the
medium  is, the more difficult is it to get rid of these intruders.
  It has been before mentioned that some have  objected to chlo-
roform  and balsam, believing that it  became clouded  after a cer-
tain time.  Perhaps this may be accounted for in part by the fact
that almost all objects have a certain amount of dampness in them.
Others are kept in some  preservative  liquid until  the time  of
mounting,  and  these  liquids  generally  contain certain  salts
(Chapter IV.).   If  this dampness, as  well as all traces of these
salts, however small, are not totally removed—the former by dry-
ing, the latter by repeated  washings—the addition of  chloroform
will render the balsam much  more liable to the cloudmess than
when balsam alone  A\ras used, as before mentioned. 
62
PREPARATION AND MOUNTING
  This mode of employing the balsam, hoAvever, will not be ahvays
applicable, as chloroform acts upon some substances Avhich balsam
alone does not.  Some salts are even  soluble in it, the  crystals
disappearing after  a feAV  days or Aveeks, Avhereas in the balsam
alone they are quite permanent.   Experience is the only  guide  in
some cases, Avhilst in others  a little forethought will be all that  is
required.
  The particular  methods used for certain  objects may be now
entered upon.  Many  of  the Diatomaceae and fossil Infusoria,  as
they are sometimes termed,  are mounted dry, and cleaned in the
way described in Chapter  II.  Others are almost always placed  in
balsam, except where they are intended to be used with the lieber-
kuhn and dark background, by Avhich  means some of them are
rendered exquisitely beautiful.  The usual Avay of mounting them
in balsam is as follows:—Take a drop of  the Avater  containing
them, place it upon the slide, and evaporate over the lamp, Avhilst
with  a  needle  they may  be dispersed  over  any  space  desired.
When they are thoroughly dry, drop a little balsam on one side,
and exclude the bubbles.  The slide may then be warmed to such
a degree that the  balsam, by lifting  the glass  at one end, will be
carried over the specimens, Avhich may then be covered with thin
glass, made Avarm  as before  described.   W'here the  objects are
quite dry, and loose upon the glass, it requires great care in plac-
ing the  cover upon them, otherwise  they are forced to one edge,
or altogether from under it,  in the Avave of the balsam.  For this
reason, Professor  Williamson adds  a feAV drops of gum-Avater  to
the last Avashing, which causes  them to. adhere sufficiently to the
glass to prevent any such mishap.
  Mr.  T.  G. Rylands' method  differs in some degree from the
above, and is, to use his OAvn words, as folloAvs:—Thick balsam is
preferable, and  the burnt  covers (see  Chapter II.) to be mounted
are laid in a convenient position with the diatoms upAvards.  The
slides required  having  been  carefully  cleaned  and marked on the
under side  Avith a ring  of ink, by the aid of a turntable about half
an inch in diameter to  point  out the  centre, a drop of benzole is
applied by  a large pin to the diatoms on the cover, so as to exclude
the air from the valves and frustules.  The slide is then held over
the  lamp, and when warm, a sufficiently large drop of balsam  is 
OF MICROSCOPIC OBJECTS.
63
put upon it, and heated until it begins to steam.   If small bubbles
appear, a puff of breath removes them.  The slide being held slight-
ly inclined from the operator, and the drop  of balsam  becoming
convex at its lower edge, the cover is brought in contact Avith it
at that point, gradually  laid doAvn, pressed Avith the forceps, and
brought to its central position.  When cool the superfluous balsam
(if any) is removed  Avith a heated knife-blade, the  slide cleaned
with a little turpentine,  and finished by  washing in a hand-basin
with soap and water.   In this process there is no delay  if the bal-
sam be sufficiently thick, as the slide may be cleaned  off  almost
before it is cold.
   It is noAV Avell  knoAvn that  from common chalk it  is an easy
matter to obtain interesting specimens of Foraminifera.   Scrape a
small  quantity  of chalk  from the mass and shake it  in  Avater;
leave this  a few minutes, pour  the Avater  aAvay and add a fresh
quantity, shake up as before, and repeat two or three times.  Take
a little of the residue, and spread it upon  the  slide, and Avhen quite
dry'add a  little turpentine.  When viewed  with  a power of two
hundred and fifty diameters this will generally sIioav the organisms
very Avell.   If it is desired to preserve the slides, they may be then
mounted in Canada balsam.  Mr. Guyon, in " Recreative Science, "
observes that the accumulation of the powder, by the action of the
rain or exposure to the atmospheric action, at the foot or any pro
jcction of the chalk cliffs, will afford us better specimens than that
which is " scraped," as the organisms are less  broken in the former.
   When the Foraminifera are of a larger size, though transparent
enough to be mounted  in balsam, the air must be first expelled
from the interior, otherwise the objects will be altogether unsatif-
factory.  To accomplish this they must be  immersed in  turpentii e
and submitted to the action of the air-pump. So difficult is it to
get rid of this enemy that it is often necessary to employ three or
four exhaustions, leaving them for some time under each.  When
all air has given place to the turpentine, they must be mounted in
the ordinary Avay.
   Of all objects which, are commonly met with, feAV are  such gene-
ral favourites as  the  Polycystin.-e, and  deservedly  so.   Their
forms  are most beautiful, and often peculiar—stars varying in de-
sign,  others closely resembling crowns;  the  Astromma  Aristotelis 
64
PREPARATION AND MOUNTING
like a cross, and many whose shapes no  Avords could  describe.
The greater part, perhaps, of those Avhich are usually sold, is from
the  rocky parts  of Bermuda;  but they  are also  found  in Sicily,
some parts of Africa and America.   They are usually mounted in
balsam, but are  equally beautiful mounted " dry" and used with
the  lieberkuhn.  They  require  as  much care  in cleaning as  the
Diatomaceae, but the process is  a different one.  Sometimes this
is effected by simply Avashing until  they are freed from  all extra-
neous matter, but this is seldom as effectual as it should be.   In
the Microscopic Journal Mr. Furlong gives the folloAving method
of treatment as the best  he knew :—

   Procure—
       A large glass vessel with  3 or 4 quarts of water.
       New tin saucepan holding 1 pint.
       2 thin precipitating glasses holding 10 oz. each.

Take 3  oz. of dry " Barbadoes earth" (lumps are best), and break
into rather small fragments.   Put 3  or 4 oz. of common washing
soda into the  tin and half fill  it Avith water.   Boil strongly, and
having throAvn in the earth, boil  it for half an hour.  Pour nine-
tenths of this into the large  glass vessel, and gently crush  the re-
maining lumps Avith a soft bristle brush.  Add soda and water as
before, and boil again ; then  pour off the  liquid into the large ves-
sel, and repeat until nothing  of value remains.   Stir the large ves-
sel Avith an ivory spatula, let it stand for three minutes, and pour
gently off nine-tenths of the  contents, Avhen the shells will be left,
partially freed only, like sand.
   2nd Process.—Put common  washing soda and water  into  the
tin as before, and having placed the shells therein, boil  for an hour.
Transfer to the large vessel as before, and after alloAving it to stand
for one minute pour off.   Each Avashing brings off a kind of " flock,"
which seems to be skins.
   3rd Process.—Put the shells in precipitating glass and drain
off the Avater until not more  than \ oz. remains.   Add half a tea-
spoonful of bicarbonate of soda,  dissolve, and then pour in gently
1 oz. of strong sulphuric  acid.   This liberates the " flock," &c,
and leaves the shells beautifully transparent.   Wash Avell now with
Avater to get rid of all salts and other soluble matter. 
OF MICROSCOPIC OBJECTS.
65
  Some of the large shells are destroyed by this method, but none
that are fit for microscopic use.  An oblique light shoAvs these ob-
jects best.
  These are sometimes treated in the manner  described in Chap-
ter  II. Avhere the diatoms are spoken of, but many forms are liable
to be injured by this severe process.
  It  has been  before stated that some of the  zoophytes  may be
mounted dry, and others examined as opaque or transparent ob-
jects  according to their substance.   They  are  very interesting
Avhen examined in  the trough Avhilst living, but to preserve many
of  them for  future examination  they must  be mounted  in some
preservative medium.   Sometimes  this may be one of the liquids
mentioned in Chapter IV., but if possible they should be kept in
balsam, as there is  less danger of injury by accident to this kind of
slide.  This method of mounting presents some  difficulties, but I
think that all agree as to the trustAvorthiness of Dr. Golding Bird's
information on the subject, Avhich appeared in  the Microscopic
Journal.   Of this,  space forbids me to give more than a condensed
account, but I  hope to  omit nothing of moment to the reader for
whom these  pages are written.
   After stating that there are feAV AA'ho are not familiar with these
exquisite forms, and have not regretted the great loss of beauty
they sustain in dying,  he informs us that  from their so obstinate-
ly  retaining air in the cells and tubes Avhen  dried, it is  hardly
 practicable to get rid of it; and they also shrivel  up very seriously
 in  the process of  drying.   The folloAving  plan, however, he  has
 found almost faultless in their preparation.
    To preserve them  with  extended  tentacles, they  should be
 plunged  in cold fresh  water, which  kills them so  quickly  that
 these  are not often retracted.   The specimens  should be preserved
 in  spirit until  there is leisure to prepare  them ;  if, however, they
 have been dried, they should be soaked in cold water for a day or
 two before being submitted to the following processes :—
    1.  After selecting perfect specimens of suitable size, immerse
 them in water heated to about 120°  and place them under the
 receiver of an air-pump.  Slowly  exhaust the air, when  bubbles
 will arise and the water appear to be in a state of active ebullition.
 After a  few minutes re-admit the air and again exhaust, repeating
                               4* 
66               PREPARATION AND  MOUNTING
the process three or  four times.   This will displace the air  from
most, if not all, of the class.
   2. Remove the specimens and alloAv them to drain upon blotting-
paper for a few seconds;  then place them in an  earthen  vessel
fitted with a cover, and previously heated to about  200°.   This
heat may be easily got by placing the vessel for a  short time in
boiling Avater, wiping it immediately before use with a thick cloth.
The specimens are then dropped into  this, covered Avith the lid,
and immediately placed  under the receiver of the air-pump, and
the air rapidly exhausted.   By this means they are dried complete-
ly, and so quickly that the cells have no time to wrinkle.
   3. In an hour or two remove them from the air-pump and drop
them into a vessel of perfectly transparent camphene.   This may
be quite  cold when the horny, tubular polypidoms, as those  of the
Sertulariae, are  used; but should be  previously heated to 100°
when the calcareous, cellular Polyzoa are the objects to be pre-
served.   The vessel  should be covered  Avith a  Avatch-glass and
placed under the receiver, the air being exhausted and re-admitted
two or three times.
   4. The slide which is  to receive the specimen should be well
cleaned and warmed so as to alloAv the balsam to flow freely over
it.  This must be applied in  good quantity,  and air-bubbles re-
moved with  the needle-point.  Take  the polypidom from  the
camphene, drain it  a little, and Avith the forceps immerse it  fully
in the balsam.   The glass to be laid upon it should be warmed
and its surface covered Avith a thin layer of balsam, and then low-
ered gradually upon it, Avhen no bubbles should be imprisoned.
A narrow piece of  card-board at each end of the  object for the
cover to rest upon, prevents any danger of crushing the specimen.
   This mode of mounting polypidoms, &c, seems to give almost
the complete beauty of the fresh specimens.   They are very beau-
tiful objects when viewed with common light, but much more so
when the polarizer is used (in the manner described a little far-
ther on).
   To the above instructions there can be little to add ;  but I may
here mention that some young students may not be possessed of
the air-pump, and on this  account put aside all search for  those
specimens which  need little looking for at the seaside.   Many of 
OF MICROSCOPIC OBJECTS.
67
 these, however, though they lose some beauty by the ordinary
 mode of drying, will by steeping for some time in  turpentine not
 only be  freed  from the air-bubbles, but suffer so little contraction
 that they are a Avorthy addition to the cabinet.
   Another class of objects is the spicula met with in sponges, &c.
 These are often  glass-like in appearance and of various shapes;
 many are  found  resembling  needles  (Avhence their name);  some
 from the synapta  are anchor-like,  Avhilst others are star-like and
 of complex and  almost indescribable combinations.  As some of
 these  are  composed of silex and are consequently not injured by
 the  use of nitric acid, the  animal substance may be got rid of by
 boiling them in  it.  Those, hoAvever, which are calcareous must
 be treated Avith a  strong  solution of potash instead; but which-
 ever Avay is used,  of course  they must  afterwards be freed from
 every trace of  residue by careful washing.
   These  spicules  may be often found amongst the sand which
 generally accumulates at the  bottom of the jars in Avhich sponges
 are kept by those Avho deal in them, and must be picked out Avith
 a  camel-hair pencil.   The  specimens obtained by this means -will
 seldom if ever  require any cleaning process, as they are quite free
 from animal matter, &c.
   In the former chapter was noticed those insects or parts of
 them which are usually mounted dry.   When they are large and
 too opaque to admit of the  dry treatment, they must be preserved
 in Canada balsam or fluid.   The first of these may now be con-
 sidered.
   It may be here mentioned, that Avith  these objects much heat
 must not be employed, as  it  Avould  in some instances give rise to
 a cloudiness, and almost invariably injure them.
   In killing the insect it is necessary not to rub or break any part
 of it.  This may be performed by placing it in a small box half
 filled with  fragments of fresh laurel leaves, by immersion in tur-
 pentine or strong spirit, as also  in solutions of various poisonous
 salts.  After which  it may  be  preserved for some time in turpen-
 tine  or  other  preservative liquid (Chapter  IV) until  required.
 As an assistance to the student, I believe that I  can do no better
that  give  him the plan pursued by  my friend Mr. Hepworth,
whose specimens are in every Avay satisfactory; but  when his me- 
68
PREPARATION AND MOUNTING
thod is used, the insects must not have been placed in turpentine
for preservation:—
   " After destroying the insects in chloroform or sulphuric ether
(methylated being cheaper), wash them thoroughly in a Avide-ncck-
ed bottle, half-filled, Avith  tAvo or three waters; the delicate ones
requiring great care.  Then immerse them in liquid potash (or
Brandish's solution, Avhich is stronger than the usual preparation),
and  let them remain  a longer or shorter time according to their
texture.   When  ready to remove, put  one by  one into a small
saucer of clear Avater, and with a camel-hair pencil in each hand
press them flat to the bottom, holding the head and thorax with
the left-hand brush, and apply pressure with the other from above
downwards, giving the  brush  a rolling motion, Avhich  generally
expels the contents of the abdomen  from the thorax.  A minute
roller  of pith  or cork might be used instead of the brush.  In
larger objects, use the end of the finger to flatten them.   Large
objects require more frequent Avashing, as it is desirable to remove
the potash thoroughly, or crystals are apt to form after mounting.
Having  placed them  on the slides  Avith  thin  glass covers, tied
down  with thread,* dry and immerse them in rectified spirits of
turpentine ; place the vessel under the receiver of an air-pump, and
keep it  exhausted  until  the turpentine has taken the place of the
air-bubbles: they are then ready for the application of the balsam.
Larger objects may often Avith advantage be transferred to a clean
slide, as during  the drying there is considerable contraction, and
an outline often  remains beyond the margin shoAving this.  When
closely corked they may remain in the spirits tAvo or three months.
As you take them  from  the bottle Avipe as much turpentine off as
possible before removing the  thread, and  when  untied carefully
wipe again, placing the finger on one end of the cover Avhilst you
Avipe the other,  and vice versa.  By this means you remove as
much  turpentine from under the cover as is necessary; then drop
the  balsam, thinned with chloroform (see  Chapter  I.), upon the
slide, letting the fluid touch the cover, when it will be taken in
between the surfaces  by capillary attraction;  and after pressing
  * This applies to the more delicate ones, which will not bear transferring
after being once spread out and dried. 
OF MICROSCOPIC OBJECTS.
69
the cover down  it may be left to dry, or you may hold the slide
over  a  spirit-lamp for  a  feAV seconds before pressing  down  the
cover.  If heat is not applied, they are much longer in drying but
are more transparent.  If made too hot the boiling disarranges
the objects, and if carried too far will leave only the resin of  the •
balsam, rendering it so  brittle that the cover is apt to fly off by a
fall or any jar producing sufficient percussion.  Never lift the cover
up if possible,  during the operation, as there is danger of admitting
air.   A feAV bubbles may  appear immediately after mounting,  but
generally subside after  a few hours,  being only the chloroform or
turpentine in a state of vapour,  which becomes condensed."
   This  method of preparing and mounting  insects I can strongly
recommend as giving first-rate results; but  Avhere the  specimens
are small they seldom  need the soaking in caustic potash which
larger ones must have.  It is only necessary to leave them awhile
in turpentine, especially Avhen they have been first dried Avith gen-
tle pressure between two glasses, and then mount Avith balsam in
the ordinary Avay.
   Amongst the insect tribes there is abundant employment, espe-
cially for the  lower powers of the microscope.  But if the deep-
er Avonders  and beauties of the animal economy are to be sought
out and studied,  it is desirable that the various parts should be set
separately, in  order that  they may  receive'a more undivided at-
tention, as well as to render them capable of being dealt Avith un-
der the higher powers.  We will, therefore, briefly consider  the
treatment Avhich  the different portions require.
   The  eyes  of the butterflies,  and  indeed  of almost  all insects,
afford materials for a study Avhich is complete in  itself.   When
examined Avith a tolerably high  poAver, instead of finding each  eye
with  an  unbroken spherical surface, it is  seen that many are com-
posed of thousands of  hexagonal divisions, each being the outer
surface  of a separate portion termed the ocellus.   In others these
divisions are  square; but in  all there is a layer of dark pigment
surrounding their lower parts.   The ocelli may be partly removed
from the eye, Avhich will show  how their tapering forms  are ar-
ranged.   But here we have to consider how to place them in bal-
'sam  for preservation.   The  eye being removed  from the insect,
and the dark pigment removed by the use of a camel-hair pencil, 
70               PREPARATION AND  MOUNTING

must be allowed to remain in turpentine at least for some c'ayp.
The turpentine should then be reneAved and the eye Avell Avashed
in it just  before it is to be mounted.   It may then  be set in bal-
sam in  the  same Avay as any other object;—but here a difficulty
is met Avith.   The eye being spherical upon the surface  required,
must necessarily be  " folded" or broken in attempting to flatten it.
This difficulty may  be often  overcome by cutting  a number of
slits round the edges; but some object to this mode of treatment,
and Avhere it is practicable it is much more satisfactory to mount
one  in the natural rounded form and another flat.   Instead, hoAV-
ever, of mounting the organ whole, four or five slides may be pro-
cured from  each of the larger ones, as those of the Dragon-fly,
&c.
  The antenna? also are often mounted on separate slides, as being
better suited for  higher poAvers and more minute examination than
when connected with the  insect.  These tAvo projecting organs,
issuing from the head,  are jointed, and moveable at will.   They
differ very much in form amongst the various species, and are well
worth the  attention of the microscopist.  They are usually mount-
ed  with the head attached, and perhaps they are more interest-
ing when  thus seen.  Some few are very opaque, to prepare which
the following method has been advised :—
  Bleach  the  antennae  by soaking in the following solution for a
day or two:—

                 Hydrochloric acid, 10 drops.
                 Chlorate of  potash, \ drachm.
                 Water, 1 oz.

This will  render  them transparent.   Wash well, dry, and mount
in Canada balsam.  Instead  of the  above,  a  Aveak solution  of
chloride of lime  may be used, by which means the nerves will be
well shown.   Many, hoAvever, are rendered transparent enough by
simply soaking in turpentine for a longer or shorter time.  Where
the  antennae, hoAvever,  are "plumose," or feather-like, extreme
care is required in mounting, though the difficulty is not so great,
as some seem to think.  If they are first dried with gentle pres-
sure, and  then subjected to the action of the air-pump in a small 
                 r  OF MICROSCOPIC OBJECTS.                7l

 quantity of turpentine until  the  air is thoroughly expelled, they
 can be easily finished upon the slide, especially when balsam and
 chloroform are used.
   Insects  supply us Avith  another series of beautiful objects, viz.,
 the feet*  These are  sometimes simply dried and mounted with-
 out any medium, as before mentioned ; but most of them are ren-
 dered much more fit for examination by using balsam in their
 preservation,  as  it greatly   increases their  transparency.   The
 smaller kinds may be  dried Avith gentle pressure betwixt blotting-
 paper, and then immersed for some  clays in turpentine, Avithout
 requiring the treatment with liquor potassae.  This immersion will
 render them beautifully transparent, Avhen they may be mounted
 in balsam  in the usual manner.
   It  is, however, sometimes  found difficult to fix the feet Avhen
 expanded, in which  state  the interest of the object is greatly in-
 creased.  Mr.  Ralph  recommends the folloAving  mode :—" First
 Avash the  feet, Avhile the insect is yet alive, Avith  spirits of wine;
 then  holding it  by a  pair of forceps close to the edge of a clean
 piece of glass, the insect Avill  lay hold of the  upper surface by its
 foot, then  suddenly drop another  small piece of  glass over it, so
 as  to retain the foot expanded, and cut it off with a pair of scis-
 sors, tie up and soak to get rid of air."  Mr.  HepAvorth says that
 he  never  found any difficulty in expanding the foot on a drop of
 water  or  well-wetted  slide, and laying a thin glass cover over it,
 tying with thread, drying, and immersing  in turpentine.
  The  mouth, also, with  its organs, is an interesting object in
 many insects.  That of the common fly is often made use of, and
 is  comparatively  easy to  prepare.   By  pressing  the head, the
 tongue  (as it is  commonly termed) will  be  forced to protrude,
 Avhen it must be secured by the same means as the foot, and may
be  subjected to the soaking in turpentine, and mounted as usual.
The honey-bee is, hoAvever, very different in formation, and is Avell
Avorth another slide; indeed, even in insects of the same  class, the
 differences are many and interesting.
  Another worthy object of study is the respiration of insects,
  * See Mr. Hepworth's interesting articles on the fly's foot in the second
and third volumes of the Microscopic Journal 
72
PREPARATION AND MOUNTING
which is effected by tracheae or hollow tubes, which generally run
through  the body in one or more large trunks, branching out on
every side.  These terminate at the surface  in  openings, Avhich
are termed spiracles, or breathing organs.  The trachea? often pre-
sent the appearance of tubes  constructed by a tAvisted thread,
somewhat resembling the spiral fibres of some plants.   These are
very beautiful  objects,  and are generally mounted in'balsam, for
which reason they are mentioned here ; but as they evidently be-
long to the " dissecting portion," they will be fully treated of  in
another place.
   Amongst the parasitic insects a  great variety of  microscopic
subjects  will be found.  As these are usually small, they may be
killed by immersion in spirits of  turpentine ; and if at all opaque,
may be  allowed to remain in the liquid until transparent enough,
and then mounted in Canada balsam.
   The acarida, or mites and ticks, are well known; none, perhaps,
better than those Avhich are so often found upon cheese.  Flour,
sugars,  figs,  and  other eatables, are  much  infested  by them;
whilst the diseases called the itch in man, and the mange in animals,
are produced by  creatures belonging to this tribe.  These animals
are sometimes mounted by  simply steeping them in turpentine,
and proceeding as with other insects.  The  " Micrographic Dic-
tionary" gives the folloAving directions as to mounting parts of
these :—" The parts of the mouth and the legs, upon Avhich the cha-
racters are usually founded, may be best made out by  crushing the
animals  upon a slide  with a thin glass cover, and Avashing away
the exuding substance with water; sometimes  hot  solution  of
potash is requisite, with the subsequent addition of acetic acid and
further  Avashing.   When afterwards dried and immersed in Canada
balsam, the various parts become beautifully  distinct,  and may  be
permanently preserved."
   Feathers of different kinds of  birds are usually mounted in bal-
sam when  required to show much of  the structure.  This is par-
ticularly interesting when the feathers are  small, as  they  then
show the inner substance, or pith, as  it may be termed, Avith the
cells, &c.  The " pinnae," or soft branches of the feathers, will be
found of various constructions; some  possessing hooks along one
side, whereby they fasten themselves to their neighbours; others 
OF MICROSCOPIC OBJECTS.
73
branching out, with straight points somewhat resembling the hairs
from certain caterpillars.  But, of course, when the metallic-look-
ing gorgeous colours are all that is required to be shoAvn, and re-
flected  light used (as with the  feathers  of the humming-bird,
peacock, &c), it is much better that they should be mounted dry,
as in Chapter II.
   The seeds and pollen of plants are  most frequently mounted dry
as mentioned in Chapter II.; but the more transparent of the for-
mer, and the darker  kinds  of  the latter, are perhaps better seen
in Canada balsam.  There is nothing particular to be observed in
the manipulation, except that  the glass cover must be  applied
lightly, otherwise  the grains may be crushed.  There are  some
objects which cannot be shown in a  perfect manner when mount-
ed dry, but Avhen immersed in balsam become so very transpa-
rent that they  are almost useless. To avoid this, it has been re-
commended to stain the objects any colour that may be conve-
nient,  and aftenvards mount  in balsam  in  the ordinary  man-
ner.
   Most objects intended for the polariscope may be mounted in
Canada balsam ; but  there are  some  exceptions to this.   Many of
the salts are soluble in this medium,  or their forms so  injured by
it, that glycerine or oil has  to be used (see Chapter IV.); others
must be left in the dry form, as before mentioned;  and some feAV
it is impossible to preserve unchanged  for any  length  of  time.
Crystals, however, are amongst the most beautiful and  interesting
subjects for polarisation ;  and it is very probable  that,  by the  aid
of the polariscope, new and A'aluable facts are yet to be made
knoAvn.  For one avIio finds pleasure in form and colour, there is
a field here which Avill only  open wider upon him as he advances;
and instead of being in anywise a merely mechanical occupation,
it requires deep and careful study.   The little here said on the
subject Avill shoAv  this in some degree.
   With almost every salt the  method of crystallization must be
modified to obtain the best forms;  I may even  go further than
this, and say that  it  is possible  to change these  forms to such a
degree that the eye can perceive no relationship to  exist betAvixt
them.   If a solution of sulphate of iron is made, a small quantity
spread evenly upon a slide,  and then suffered to dry  whilst in a 
74               PREPARATION  AND MOUNTING

flat position, the crystals often resemble the fronds of the common
fern in shape.  But if, Avhilst the liquid is evaporating, it is kept
in motion by stirring Avith a thin glass rod, the crystals form sepa-
rately, each rhombic prism  having its angles avcII defined, and
giving beautiful colours with the polarized light.  Again, pyro-
gallic acid, Avhen allowed  to flow evenly over the slide in a satu-
rated solution, covers the surface in long "needles," Avhich are
richly  coloured by  polarized light; but  if any small  portion of
dust or other  matter should form a nucleus around Avhich these
"needles" may gather, the beauty is Avonderfully increased.  A
form very closely resembling the "eye"  of the peacock's tail, both
in form and colour, is then produced, Avhich to one uninitiated in
crystallography bears very little resemblance to the original crys-
tal.  From these simple facts it will  be clearly seen that in this,
as in every other department, study and experience are needful to
give the best results.
  To obtain anything like uniformity in the formation- of crystals
upon the glass slide, every trace of grease must  be removed by
cleaning with liquor potassae or ammonia immediately before using,
care also being taken that none of the agent is left upon the slide,
otherwise it may interrupt and change their relative position, and
even their form.
  Amongst those Avhich are generally esteemed, the most beautiful
are the crystals of oxalurate of am.nonia.  The preparation  of this
salt from uric acid and ammonia is a rather difficult process, and
will not on that account be described here ; but  Avhen possessed,
a small quantity of a strong solution in Avater must  be made, and
a little placed  on the slide, and evaporated sloAvly.   Part of the
salt will then be deposited in circles Avith the  needle-like crystals
extending from common centres.  They should then be mounted
in pure Canada balsam ; and,  when the best colours are wanted,
used with the. selenite plate.   Of  this class of crystal, salicine is
a universal favourite, and can be easily procured of most chemists.
The crystals may be produced in tAvo Avays:—A  small portion of
the salt must be placed upon the slide,  and a strong  heat  applied
underneath  until fusion ensues; the matter should then be evenly
and thinly spread over the surface.   In a short time the crystals
Avill form, and are  generally larger than those procured by the 
OF MICROSCOPIC OBJECTS.
75
folloAving process ; but  the uncertainty is increased a little when
fusion  is used, Avhich,  however,  is desirable  with  many salts.
Secondly, make a saturated solution of salicine, Avhich in cold water
is effected by adding one part of the salt to eighteen parts of Avater.
Lay a little upon the slide, and allow it to evaporate spontaneously,
or Avith the aid of gentle heat.  The crystals are generally uniform,
and with ordinary poAvers quite large enough to afford a beautiful
object.   The circular shape and gorgeous  colours of  this crystal
have made it so great a favourite that there are few cabinets with-
out it.
  Many  new forms may be procured by uniting two totally dif-
ferent  salts in solution in certain proportions.   This is a field af-
fording neAv facts and beauties;  but requires some chemical know-
ledge and much perseverance to obtain very valuable results.  One
of  the most beautiful I have met Avith has been composed of sul-
phate of copper and sulphate of magnesia.   The flower-like forms
and uniformity of crystallization  when successful  make it Avell
worth  a feAV failures at first; and as  I became acquainted  Avith
some neAv facts in my frequent trials, I will give the preparation
of the  double salt from the beginning. •
  Make  a saturated solution of the tAvo sulphates, combined in the
proportion of three parts copper to one  part magnesia, and  then
add to the solution  one-tenth of pure Avater.  Dust or other im-
purities  should be guarded against, and the slide made free from
all  trace of grease by cleaning immediately before use Avith liquor
potassae  or ammonia.  A drop of the solution should then be placed
upon the  slide, and  by a thin  glass rod spread evenly upon the
surface.   Heat this Avhilst in a  horizontal position until the salt
remains  as  a viscous transparent substance, Avhich will not  be ef-
fected until it  is raised to a high degree.  The slide may noAv be
allowed  to cool, and Avhen  this is accomplished, the floAver-like
crystals  Avill be perceived forming here and there upon the plate.
When these are  at any stage  in  Avhich it is wished to preserve
them,  a  feAV seconds' exposure  to  the fire, as  Avarm as  the hand
can comfortably bear, Avill  stop the  expansion, Avhen  the portion
Avhich Ave Avish to mount should be cut off from the mass of salt
by  simply scratching the  film around,  and  pure Canada  balsam
Avith the thin glass  used.  Breathing upon the film, or alloAving  * 
76
PREPARATION AND MOUNTING
the slide to become cold and attract the moisture from the atmo-
sphere, will cause the  crystallization  to extend, and sometimes
greatly  rob the effect;  so it is necessary to mount quickly when
the desired forms are obtained.  As the crystals are very uncer-
tain  as to the place of  their formation, I may here mention that
they may be got in any part of the slide by piercing the film Avith
a needle-point; but in some degree this necessarily interferes with
the centre.  As  the cause of this has no need to be entered into
here, and has been elsewhere discussed, I shall only give the above
directions, and say that there is a great field in this branch of study
which the microscope alone has opened.
  It would be useless  to  enter into  particulars respecting  the
various  salts and treatment they require, as a great difference is
effected even by the strength of the solution.   There are some crys-
tals, also, Avhich are called forth in insulated portions, showing no
formation upon the ground; but  even when mounted in any pre-
serving fluid, and  unchanged for a year, a new action seems to arise,
and a groundAvork is produced Avhich bears little resemblance to
the original crystal.  Sometimes this  new formation adds to the
beauty of the slide; in  other  cases  the reverse is the result, the
slide being rendered almost  Avorthless.   This action, I believe,
frequently arises  from some liquid being contained in the balsam
or other mounting medium used  ; and this  is  rendered the more
probable by the crystallization being called forth  in an hour  after
the balsam diluted wdth  chloroform  is employed, Avhereas no
change  Avould have  taken place  for months  (if at all) had pure
balsam been used.
  Sections  of some of  the salts  are very interesting objects, but
the method of procuring these and their nature Avill be described
in Chapter V.
  The scales of A'arious fish  have been before mentioned as mount-
ed " dry ;" Avhen, hoAvever, they are required for polarising objects
they are  generally mounted  in balsam, and some few in  liquid.
The former method will be  considered here.
  The eel  affords a beautiful object  for this purpose.  The scales
are covered by a thin "skin" Avhich may be slightly raised Avith
a knife and then torn off, in the  same manner as the covering of
the geranium and other petals, described in Chapter II.   The re- 
                   OF MICROSCOPIC OBJECTS.                77

quired portion may then be removed ; or if a piece of skin can be
procured as stripped off in cooking, the scales may be easily taken
from the inner surface.   They must then be Avashed and thorough-
ly cleaned.  After drying, soak for a day in turpentine, and mount
in the ordinary manner Avith balsam.   This is  a good polarising
object; but the interest, and I think the beauty, is increased by
procuring a piece of eel's skin with the scales in situ, washing and
drying under  pressure, and mounting in  balsam as before.   The
arrangement  of  the scales produces beautiful " waves" of colour,
Avhich are quite  soothing to the eye after  examining some of the
very gorgeous salts, &c.
  There are many scales of fish Avhich are good subjects for the
polariscope Avhen mounted in balsam ; but as they require no par-
ticular treatment, they need no mention by name.
  Among hairs  we find some which are beautiful  when mounted
in balsam and examined by polarized light.  Some, when wanted
as common objects, are always  used dry, as before mentioned;
but if they are intended to be shown as polarizing objects, they
must be  placed in some medium.  The " Micrographic Diction-
ary" mentions a mode of making an  interesting  object by  plait-
ing two  series of white horse-hairs at an  angle, mounting in bal-
sam, and using with the polariscope.   All hairs, hoAvever, must be
steeped in turpentine  for a short time before  mounting, as they
will thus be  rendered cleaner and more transparent.  When this
is done, there is no difficulty in mounting them.
  Many of the " tongues " of fresh-water and marine mollusca are
deeply interesting and most beautiful objects Avhen examined by
polarized light.  As these are usually mounted  in balsam, I men-
tion them in this place ; but as  they must be removed from the
animals by dissection, particulars respecting them will not be en-
tered into until  Ave come to  the  part in Avhich that operation is
described (Chapter V.).
  The manner of preparing and mounting many of the Polyzoa
and Zoophytes  has been before described; but any  notice  of
polarizing objects would be incomplete without some  allusion to
them.  A small  piece of the Flustra a.vicularis, Avell prepared, is
beautiful Avhen examined in this  manner.   No selenite is needed,
and yet the colours are truly gorgeous.  It is often met with upon 
78
PREPARATION AND MOUNTING
 shells and zoophytes of a large size, and Avill Avell repay the trou-
 ble of searching for.   Many of the Sertularidae are very beautiful
 Avith polarized light,  and, indeed, no ramble upon the seaside need
 be fruitless in this direction.
   The  different starches are quite a study in  themselves, and are
 peculiarly connected Avith polarized light.  They are found in the
 cellular  tissue of  almost every plant in small Avhite grains Avhich
 vary considerably in size ; that from the potato averages one-three-
 hundredth of an inch in diameter, and that from  arroAv-root about
 one-six-hundredth.  To procure starch from any plant, the tex-
 ture  must first be broken up or ground  coarsely;  the mass of
 matter must be then well washed in gently-floAving water,  and, as
 all starch is totally insoluble in cold Avater, the grains are  carried
 off by the current and deposited where this is stayed.   In  procur-
 ing it from the potato, as Avell as many other vegetables, it is but
 necessary to reduce the substance to a coarse pulp by the aid of
 a culinary  "grater;" the pulp should then be  well agitated in
 Avater, and allowed to rest a short time, Avhen the starch  will be
 found at the bottom, its lighter colour rendering it easily distin-
 guishable from the pulp.  It should, hoAvever, be washed through
 two  or three Avaters to render  it perfectly clean.
   These grains have no  crystalline  structure, but present a very
 peculiar appearance AVhen examined Avith polarized light.   Each
 grain shows a dark cross whose lines meet at the point where it
 Avas  attached to the  plant, called  the hilum.  Round the grain,
 also, a series of lines are seen, as though it Avere put  together in
 plates.   This is more distinctly visible in some kinds than  others.
   As to  the  mounting of these starches there is  little to be said.
 If the grains are laid upon the  slide, and as small  a portion as pos-
 sible of  the balsam diluted Avith turpentine, as before  mentioned,
 be applied, they will cling to the glass and allow  the pure  balsam
 to floAv readily over them Avithout being so liable to imprison air-
bubbles Avhen the  thin glass is  put upon them.
   The raphides, Avhich Avere fully described in Chapter II., when
required for use Avith polarized light, must be mounted in balsam,
and  many are found which give beautiful  colours.  They require
no peculiar treatment, but must be washed quite clean before put-
ting  up. 
OF MICROSCOPIC OBJECTS.
79
   There is one class of  objects for the polariscope  which differs
in preparation from any  Ave have yet considered, and affords very
beautiful specimens.   Some of the plants, including many of the
grasses and the Equisetaceae (i.e.  horsetails), contain so large  a
quantity of silica, that when the vegetable  and other perishable
parts are removed, a skeleton  of  Avonderful perfection remains.
This skeleton must be mounted in balsam, the method of perform-
ing Avhich Avill noAv be considered.
   Sometimes the cuticle of the equisetum  is removed from the
plant, others dry the stem under  pressure,  Avhilst the grasses, of
course, require no preparation.  The vegetable should be immersed
in strong nitric acid and boiled for a short time; an effervescence
Avill go on  as the alkalies are being  removed, and Avhen  this has
ceased more acid should be added.   At this point the modes of
treatment differ ;  some remove the object from the acid and Avash,
and having dried, burn it upon thin  glass until  all appears  white,
Avhen it must be carefully mounted in balsam.   I think, hoAvever,
it is better to leave it in strong acid until all  the substance, except
the  required portion, is removed ;  but this Avill  take a length of
time, varying according to the mass, &c, of the plant.  Of course,
Avhen this latter method is used, the skeleton  must  be  washed
from the acid, ttc, before being mounted in balsam.
   These siliceous cuticles are readily  found.   The straws  of most
of the cereals, Avheat, oat, &c.; the husks, also, of some of these ;
many canes; the equisetum, as  before  described; and some of
the  grasses.  Many of these are everyAvhere procurable,  so that
the student can never want material for a splendid object for the
polariscope.
   In Chapter II. the scales (or hairs)  which are  often found upon
the  leaves of plants Avere mentioned as beautiful objects  Avhen
mounted dry; but some of these when detached from the leaf—
Avhich is easily  done by gently scraping it, Avhen  dried, Avith a
knife—present  brilliant  starlike and  other forms, if mounted in
balsam and used with the polariscope.  There  is a little  danger,
Avhen placing the thin glass upon the balsam, of forcing out  the
scales in  the wave of matter Avhich is  ahvays  ejected ; this may be
overcome by applying to the slide, previously to placing the  ob-
jects  upon  it, an  extremely thin covering of the balsam diluted 
80
PREPARATION AND  MOUNTING
with turpentine as before mentioned, and thus giving them every
chance of adherence ;  or by using the balsam with chloroform, as
before noticed.   These scales are much more abundant than Avas
formerly supposed, and daily new  specimens are discovered; so
that the student should always be on the look-out for them in his
researches in the vegetable world.
  Most classes  of  objects, and the treatment they require when
mounting them in  balsam, have now been considered.  The next
chapter will be devoted to the preservative liquids,  and the best
methods of using them. 
OF MICROSCOPIC OBJECTS.
81
                     CHAPTER  IV.

PRESERVATIVE  LIQUIDS,  ETC., PARTICULARLY  WHERE CELLS ARE
                            USED.

There are many  objects which would lose all their distinctive
peculiarities if allowed to become dry, especially those belonging.
to the fresh-water Algae, many animal tissues, and most of the
very delicate animal and vegetable substances in which  structure
is to be shown.  These must be preserved by immersion in some
fluid ;  but it is evident that the fluid must be suited to the kind of
matter which it is intended to preserve.  As  it often  requires
much study and trouble  to obtain microscopic objects of this class,
it is well that their preservation should be rendered as perfect  as
possible; and  for this  reason the  cells,  or receptacles of the
fluids, should be so closed that all possibility of escape should be
prevented.  The accomplishment of this is not so easy a matter
as it might appear to the inexperienced.
  Before giving any directions as to the manipulation required in
mounting the objects,  Ave must consider the different liquids and
cells Avhich  are  requisite for their preservation.  Of the former
there are a great number, of Avhich the principal may be mentioned.
  Distilled  Water is strongly recommended  by many  for
Diatomaceae and other Protophytes.  It has been, however, stated
that confervoid  growths often disturb the clearness of the liquid,
and on this account various additions are  made to it.  A lump of
camphor is often left in the bottle, so that the water may dissolve
as much as possible.   One grain of bay-salt and one of  alum are
added to each ounce of water ; or a drop or two of creasote shaken
up  Avith the ounce of  water, Avhich should be afterwards filtered.
These additions are often  made ;  perhaps each  of them good for
certain objects.
  Glycerine.—Some affirm this to  be one of the best  preserva-
tive liquids, especially for vegetable objects; but others think that
                               5 
82               PREPARATION AND  MOUNTING

it is much better when diluted with two parts of camphor-water,
prepared as above. *
  Glycerine and Gum.—This is also believed to be a very good
liquid for vegetable tissues, and is thus prepared :—

                  Pure gum-arabic..    1   oz.
                  Glycerine  ..    ..   1    "
                   Water (distilled)..    1    "
                   Arsenious acid  ..   1^ grains.

 Dissolve the arsenious acid in the cold water, then the gum, add
 the glycerine, and mix without bubbles.
   Deane's Compound.—This is  usually deemed about the best
 medium for preserving Algae, mosses, &c, and is thus prepared :—
 Soak 1 oz. of best gelatine in 4 oz. of  water until the  gelatine
 becomes  soft,  when 5 oz.  of honey heated to boiling-point are
 added ; boil the mixture, and when  it has cooled, but not enough
 to  become stiff, add \ oz. rectified spirit with Avhich 5 or 6 drops
 of creasote have been well mixed, and filter the whole  through
 fine flannel.  This compound when cold forms a stiff jelly, the use
 of which will be described elsewhere.
   Glycerine Jelly.—This mixture closely resembles the above,
 but as the  composition differs a  little it may be  mentioned here.
 It is strongly recommended by Mr. Lawrance in the Microscopic
 Journal, where he states " that the beautiful green  of some mosses
 mounted  two years  ago, is still as fresh as the day they were
 gathered;" and that  this is the only medium he knows which will
 preserve the natural colour of vegetable substances.   He takes a
 quantity of Nelson's  gelatine, soaks it for  two or three  hours in
 cold water, pours off the superfluous Avater, and heats the soaked
 gelatine until melted.  To each fluid ounce  of the gelatine, whilst
 it is fluid but cool, he adds a fluid drachm of the white of an egg.

    * Dr. Carpenter says:—" Glycerine has a solvent power for carbonate of
 lime, and should not be employed when the object contains any  calcareous
 structure.  In ignorance of this fact, the author ( Dr. C.) employed glycerine to
 preserve a number of remarkably fine specimens of the pentacrinoid larva of
 the Comatula, whose colours he was  anxious to retain; and was  extremely
 vexed to find, when about to mount them, that their calcareous skeletons had
 so entirely disappeared, that the specimens were completely ruined." 
OF MICROSCOPIC OBJECTS.
83
He then boils this until the albumen coagulates and  the gelatine
is quite clear, Avhen it is to be filtered through fine flannel, and to
each ounce of the clarified solution add 6 drachms of a mixture
composed one part of glycerine to two parts of camphor-Avater.
  Goadby's Fluid.—This is much used in the preservation  of
animal objects ;  and seldom, if ever, acts upon the colours.   It is
thus prepared—Bay-salt,  4 oz.;  alum, 2 oz.;  corrosive-sublimate,
4 grains.   Dissolve these in two quarts of boiling water and filter.
For delicate preparations some recommend that this mixture  be
reduced by the addition of an equal quantity of water ;  but where
there is bone or shell  in the  object  the  above acts injuriously
upon it, in  which case  this fluid may  be  used:—Bay-salt 8 oz.,
corrosive sublimate 2 grains, Avater 1 quart.
   Thwaites's Liquid.—This is recommended for the preservation
of Algae, &c, as having little or no action on the colour, and is
thus prepared:—Take  one part of  rectified spirit,  add drops of
creasote enough to  saturate it; to this  add  sixteen  parts of dis-
tilled water and a little prepared chalk, and filter.  When filtered,
mix Avith  an equal  quantity of camphor-Avater (as  before men-
tioned), and strain through fine muslin before using.
   Chloride  of Zinc  Solution.—In  the  " Micrographic  Dic-
tionary " this is  stated to be " perhaps the best preservative known
for animal tissues."   Persons of great experience, however, haA'e
given  a very different  opinion; but  it is certainly very useful
in  many cases where a small degree of coagulating action is not
injurious.   It is used of strengths varying according to the soft-
ness of the parts to be preserved ; the average being 20 grains of
the fused chloride to 1  oz. of distilled Avater.   To keep this liquid
a lump of  camphor  may be left  floating  in  the  bottle.  I have
heard complaints that this mixture becomes turbid Avith keeping,
but I think this must only be the case  when some  impurity has
got into the bottle.
   Carbolic Acid.—This substance has  not been  known  long
enough to Avarrant any  decided opinion upon  its merits.  A solu-
tion of 1 part of acid to  20 of water  has been  recommended on
account of its antiseptic properties.
   Castor Oil.—This is a very useful preservative for crystals and
other objects.   Many salts are quite destroyed  when Canada bal- 
84
PREPARATION AND MOUNTING
sam is used with them ;  but very fevr are acted upon by this oil.
To use it, it must be dropped in a sufficient quantity to cover the
crystal or object to be  preserved  with a thin coating of oil.   It
may be necessary sometimes to spread it with a needle or  other
instrument.   The thin glass should then be  carefully placed upon
it, so  that all air may be excluded ; and should any oil be  forced
out, owing to the quantity used being too  great,  it must be re-
moved with  blotting paper.  When the edge of the thin glass
cover and the surrounding parts of the slide are as  clean as possi-
ble, a coating of sealing-wax varnish or liquid glue must be applied
and allowed to  dry.  A second or even a third coating may be
required, but not before the previous  cover is quite dry.   These
varnishes, however, are very brittle, and it is much  safer, as a
finish, to use one of the tougher cements—gold-size, for instance—
Avhich  will render it doubly secure.
   The above  are the principal liquids,  &c, used for  preserving
objects in cells.   The different cells may be here mentioned; and
it is recommended that these should  ahvays  be kept  some time
before use in order that  the cement may become  perfectly dry;
and care must be taken that no cement be used  on Avhich  the
preservative liquid employed has any action  whatever.
   Cement  Cells.—Where the object is not very thick, this kind
of cell is generally used.   They are easily made with the turnta-
ble before described;  but when the objects to be  preserved  are
very minute, these cells need not be much deeper than the ordi-
nary circle of cement on the slide.  When, however, a compara-
tively great depth is required, it is sometimes necessary to make
the wall of the cell as deep as possible, then allow it to dry and
make  another addition.   Of these  cements gold-size is one of the
most trustworthy, and may be readily used  for the shallow cells.
The asphaltum and india-rubber,  before noticed,  I have  found
very durable when ..well baked, and exceedingly  pleasant to work
with.   It may be used  of  such a thickness  as to give space  for
tolerably large objects.   Black japan also is much used.   Many
cements, hoAvever, which are recommended  by some writers,  are
worse than useless, owing to the brittleness which renders their
durability uncertain, as sealing-wax varnish,  liquid-glue, &c.
   The student may feel himself at a loss in choosing the cement 
OF MICROSCOPIC OBJECTS.
85
which will give him the safest cells, many of them becoming par-
tially or wholly dry in a year or two, as stated  in another place.
I can only give him a few general directions, and  he must then
use  his OAvn judgment.  Of course  it would be lost labour to
employ any cement upon which  the  preservative liquid has any
action whatever.   It is also a good rule to avoid those in whose
composition there are  any  particles which do not  become a
thorough and intimate portion, as these unreduced fragments will
almost  certainly, sooner or later, prepare  a road by  which the
liquid will escape;  and, lastly, whatever cement he  uses, the cells
are always better  when they have been kept a short time  before
use, as already stated.
   Gutta-percha Rings have been  recommended by some, as
affording every  facility for the manufacture of  cells for liquids;
but  they cannot be recommended, as, after a certain length of
time, they  become so brittle as  to afford no  safeguard against
ordinary accidents.
   Often the  cells must necessarily be of a large size, and for this
reason are made by taking four strips of glass of  the  thickness
and  depth required, and grinding the places where these  are to
meet with emery, so as to form a  slightly roughened but flat edge.
The glass strip must also be ground  on  the side where it meets
the plate, and each  piece cemented Avith  the marine  glue men-
tioned in Chapter I. in  the following manner :—On that part of
the glass to Avhich another piece  is to be attached should be laid
thin strips of the glue ; both pieces must then be heated upon a
small brass  table, with the aid of the spirit-lamp, until the strips
become melted ; the small piece is then to be taken up and placed
upon the spot to which  it is to be attached, and so on until the
cell is completed.   It will be found necessary to  spread the glue
over the surface required Avith a needle or some other instrument,
so that an unbroken line may be presented  to the Avail of the cell,
and no  bubbles formed.  Too great a heat will  " burn " the ma-
rine-glue, and render it brittle ;  care  must be therefore taken to
avoid this.            f
   When shallow cells are required,  those which  are made by
grinding a concavity in the middle of an  ordinary slide will be
found very convenient.  The concavities are cut both circular and 
86
PREPARATION AND MOUNTING
oblong; and the surface being flat, the cover is easily  fastened
upon it.   These are now cheap, and are very safe as to leakage.
  Circular cells with a flat bottom used to be made by drilling a
hole through glass of the required thickness, and fixing this upon
an  ordinary slide with marine-glue; but  the danger of breakage
and the labour Avere so great that this method is seldom used now,
and, indeed, the rings about to  be mentioned do  away with all
necessity of it.
  Glass Rings.—Where any depth is required,  no method of
making a cell for liquids is so convenient as the use of glass rings,
which  are noAV easily and cheaply procurable.  They are made of
almost every size  and depth, and,  except in very extraordinary
cases,  the  necessity  for building cells is  completely done away
with.   These rings  have  both edges left roughened, and  conse-
quently adhere very well to the slide, this adherence being gene-
rally accomplished by the aid of marine  glue, as  before noticed
with the glass cells.   Gold-size has been occasionally used for this
purpose ;  and the adherence, even with liquid in the cell,  I have
always found to be perfect.  This  method has  the  advantage of
requiring no heat, but the gold-size must be perfectly dry, and
the ring must  have  been fixed upon the  slide some time  before
use.  Canada balsam has also been used for the same purpose, but
cannot be recommended, as Avhen it is perfectly dry it becomes so
brittle  as to bear no shock to which the  slide may  be ordinarily
exposed.
  These are the  cells  which are mostly  used in this branch of
microscopic mounting.   The mode of using them, and the dif-
ferent  treatment  which certain objects require when intended to
be preserved in the before-mentioned liquids, may now be inquired
into.
  I may mention, however,  that this class  of objects is looked
upon by many  with  great mistrust, owing to the danger there is
of bubbles arising in the cells after the  mounting has been com-
pleted, even for years.   I  know some excellent microscopists Avho
exclude all objects in cells and  preservative liquids from their
cabinets, because they say that eventually almost all become dry
and worthless;  and this is no matter of surprise, for many of them
do really become so.   Perhaps this is owing to the slides being 
OF MICROSCOPIC OBJECTS.
87
sold before they could possibly be thoroughly dry.  As to the air-
bubbles, I shall have something to say presently.
  We will now suppose the cell employed is made by placing a
glass ring upon the slide with marine glue or gold-size, and is quite
dry.  Around the edge of the cleaned thin glass Avhich is to cover
it,  I trace  with a camel-hair pencil  a ring of gold-size, and also
around the edge of the cell to Avhich it is to adhere.  Dr. Carpen-
ter objects to this, as rendering the  later applications of the gold-
size liable to " run in."   All danger  of this, however, is complete-
ly done away with by leaving the slide and cover for aAvhile until
the cement becomes partially " fixed,"  but still adhesive enough
to perform its  function (Chapter II.).  With many slides this  is
not accomplished in less than twenty-four hours, even if left tAvo
or  three days no injury whatever ensues ;  but Avifh other kinds an
hour is too long to  leave the exposed cement, so that the opera-
tor must use his OAvn  discretion.   The liquid required  may  be
drawn up by the mouth into the pointed tube mentioned in Chap-
ter I., and then transferred to the cell.  In the various books of
instruction, the object is now to be  placed in the cell; this, how-
ever, I think a great mistake,  as another process is absolutely
necessary before Ave advance so far.   The  cell, full  of liquid, must
be placed under the receiver of  an air-pump, and the  air with-
drawn.  Almost immediately it will be perceived that the bottom
and sides of the cell are covered with minute bubbles, Avhich are
formed by the air that is held in suspension by the liquid.  The
slide may now be removed, and the bubbles may require  the aid
of a needle  or other point to  displace them,  so  obstinately  do
they adhere  to the surface of the glass.  This process  may be
then repeated, and  one cause, at least, of  the appearance of bub-
bles in cells of liquid will be got rid of.  The object to be mounted
 should also be  soaked in one or  two changes of the  preservative
 liquid employed, and, during the soaking, be placed under the
 air-pump  and exhausted.   It may then be transferred to the cell,
 which  Avill probably cause  the liquid to  overfloAV  a  little.   The
 cover with the gold-size applied to the edge  must then be care-
 fully laid upon the  cell, and slightly pressed doAvn, so that all air-
 bubbles may be displaced.  The tAvo portions of gold-size will
 noAV be found to  adhere  Avherever the liquid  does not remain, 
88
PREPARATION AND  MOUNTING
 although the whole ring may have been  previously wet.  The
 outer edge of the thin glass and cell must now be perfectly dried,
 and a coating of gold-size applied.   When this is dry, the process
 must be repeated  until the cement has body enough to protect
 the  cell from all  clanger of leakage.  When some preservative
 liquids are used, a scum is frequently found upon the surface when
 placed in the cell, which must be removed immediately before the
 cover is laid upon it.
   I believe  this method to be perfectly secure against leakage
 when carefully  performed; and some of  my friends have told
 me that their  experience  (some years)  has been  equally satis-
 factory.
   In using some of the particular kinds of preservative liquids, it
 will be found necessary to make slight change in the  manipulation.
 This will be best explained by mentioning  a few objects, and the
 treatment they require.
   For the preservation of the Mosses, Algae, &c,  Deane's com-
 pound is much used, and considered one of the best media.  The
 specimen to be  mounted should be immersed in the  compound,
 Avhich must be kept fluid by the vessel containing it being placed
 in hot water.  In this state the whole should be submitted to the
 action of the air-pump, as it is not an easy matter to get rid of
 the bubbles which form in and around the objects.   The cell and
 slide must be warmed; and heat will also be necessary to render
 the gelatine, &c, fluid enough to flow from  the stock-bottle.  The
 cell may then be filled Avith the compound, and the  specimen im-
 mersed in  it.   A thin glass cover must then be warmed,  or gently
 breathed upon, and gradually loAvered upon the cell, taking care,
 as with all liquids, that no bubbles are formed by the operation.
 The cover may be fixed by the aid of gold-size, Japan, or any of
 the usual varnishes, care being taken, as before, that all  the com-
 pound is removed from the parts to Avhich the varnish  is  intended
 to adhere.
   The glycerine jelly of Mr. Lawrance, before mentioned, requires
 almost a similar treatment.   " The objects  to be mounted in this
medium should be immersed  for some time in a mixture  of equal
parts  of glycerine and dilute alcohol  (six  of  water to one  of
alcohol).  The  bottle of  glycerine jelly must be placed in a cup 
OF MICROSCOPIC OBJECTS.
89
of hot water until  liquefied, when it must be  used like  Canada
balsam, except that it requires less heat,  A  ring of asphaltum
varnish round the thin glass cover completes the mounting."
  The Infusoria  (see  Chapter III.) are sometimes  preserved in
liquid; but present many difficulties to the student.  Different
kinds  require different treatment, and consequently it  is well,
when practicable, to mount similar objects in tAvo or more liquids.
Some  are  best preserved in a strong  solution  of chloride of cal-
cium, others in  Thwaites's liquid, whilst a  feAV keep their colour
most perfectly when in glycerine alone.   Many of them, hoAvever,
are so very  transparent that they present  but faint  objects for
ordinary observance.  The Desmidiaceae require someAvhat simi-
lar  treatment,  and may be mentioned  here.   The  solution  of
chloride  of calcium has been strongly recommended ;  but no pre-
servative  liquid  seems to be  without some action upon them.
Both of  the above  classes of objects  should be mounted in shal-
low cells, so as to allow as high a microscopic power as  possible
to be used with them.
   Many  of the Zoophytes which are obtained on  our sea-coasts
are  well preserved  by mounting in  cells, in the manner before
mentioned, with  Goadby's fluid, or distilled Avater Avith one of the
additions noticed amongst the preservative liquids.   For examina-
tion by polarized light, however, they are usually mounted in bal-
sam (see Chapter III.), Avhilst those in cells present a more natural
appearance as to position, &c, for common stud v.
   As to  the use of preservative liquids Avith the Diatomaceae there
are various opinions.  Some  experienced microscopists say that
there is  little or no satisfaction in mounting them in this Avay.
Dr.  Carpenter, hoAvever,  explains this difference by his  instruc-
tions as  to what method should be used Avhen certain ends  are
desired.   He says: " If they can be obtained  quite fresh, and it
be  desired that they should  exhibit as closely as possible  the
appearance presented by the living plants, they should be put up
in  distilled water within cement-cells; but if they are not thus
mounted within a short time after they have been gathered, about
a sixth part of alcohol should be added to the water.   If it be
desired to exhibit the stipitate forms in their  natural parasitism
upon  other  aquatic plants, the entire mass may be mounted in
                               o 
90
PREPARATION AND MOUNTING
 Deane's gelatine in a deeper cell;  and such a preparation is a very
 beautiful  object for the  black-ground illumination.   If,  on  the
 other hand, the minute structure of the siliceous envelopes is the
 feature to be brought into view, the fresh diatoms must be boiled
 in  nitric  or hydrochloric acid " (which process is fully described
 in Chapter II.).  It is very convenient to have many  of these ob-
 jects mounted by two or more of the above methods ; and if they
 are  to  be studied, this is indispensable.  Mr.  Hepworth once
 shoAved me about one hundred slides which he had  mounted in
 various ways, for no other purpose than the study of the  fly's
 foot.
   My friend, Mr. Rylands, successfully mounts the diatoms in the
 state in which  he finds them,  and gave me the folloAving method
 as that which  he always  employs.  He says that he has had no
 failures, and hitherto has found his  specimens unchanged.  Take
 a shallow ring cell of asphalt or black varnish (which must be at
 least three weeks old),  and  on the  cell, whilst revolving, add  a
 ring of  benzole  and gold-size  mixed in equal  proportions.  In a
 minute  or two pure  distilled water is put in the cell until the sur-
 face is  slightly convex.  The  object having been already floated
 on to the cover (the vessel used for this purpose being an ordinary
 indian-ink palette), is  now inverted and laid  carefully  upon  the
 water in the  cell.   By these means the object may be laid down
 without being removed.  The  superfluous  moisture must not be
 ejected by pressure, but a wetted camel-hair pencil, the size made
in an ordinary quill, being partially dried by draAving  through the
 lips, must be used repeatedly to  absorb it, which the pencil will
 draw by capillary attraction as it  is very slowly turned  round.
 When the cover comes in contact  Avith the benzole and gold-size
 ring, there is no longer any fear of the object being removed, and
 a slight pressure with the end of the cedar stick of the pencil will
render the adhesion complete,  and cement the cover  closely and
firmly to the  cell.  When dry,  an  outer ring of asphalt makes the
 mounting neat and complete.
  The Fungi have been before mentioned; but  it may be here
stated that some few of the minute forms are best preserved in a
very shalloAV cell of liquid.  For this purpose creasote-water may
be advantageously used. 
OF MICROSCOPIC OBJECTS.                91
  The antenna? of insects have been before noticed as  being very
beautiful when mounted in balsam.   This" is readily accomplished
when they are large; but those  of  the most  minute  insects  are
much more difficult to deal Avith, and are less liable to injury when
put up in fluid.   Goadbfs Fluid serves this purpose very well;
but, of course, the object must be thoroughly steeped in the liquid
before it is mounted, for a longer or  shorter time according to  the
thickness.
  The eggs of insects afford some worthy objects for the microscope,
amongst which may be mentioned those of the common cabbage
butterflies  (small and great), the  meadoAv-broAvn, the  puss-moth,
the tortoiseshell butterfly, the bug, the coAv-dung fly, <fcc.   These,
however, shrivel up on becoming dry, and must, therefore, be pre-
served in some of the  fluids  before mentioned.   To  accomplish
this no particular directions are required; but the soaking in the
liquid about  to be employed, &c, must  be attended  to as with
other objects.
   Glycerine  may be advantageously used for the preservation of
various insects.  These should first be  cleaned with alcohol to get
rid of all extraneous matter, and then, after soaking in glycerine,
be mounted with it like other objects.  This  liquid may also be
used for the Entomostraca, which offer  a Avide  field for  study.
They are to be found abundantly in  ponds of  stagnant water,  &c.
Some insects, such as May-flies, &c, are, however,  often preserved
by  immersion in a solution of one part of chloride of calcium in
three or four parts of Avater; but this has not been recommended
amongst the " preservative  liquids," as the colour, Avhich  is often
an attractive quality of this class  of  objects, is thereby destroyed.
  We have now noticed the treatment Avhich must be applied to
those objects which are to be preserved in liquids  and cells.   We
may here state that all  slides of  this kind should be examined at
short  intervals, as  they will be found noAV and  then to require
another coating of varnish round the edge of  the thin glass cover
to prevent all danger of leakage.  The use of the air-pump, in the
first instance (as before recommended), and this precaution as to
the  varnish,  will render the slides   less  liable to leakage and air-
bubbles, which so very frequently render them almost worthless. 
92               PREPARATION AND  MOUNTING
                      CHAPTER  V.

SECTIONS AND HOW TO CUT THEM, WITH SOME REMARKS ON DIS-
                           SECTION.

Many  objects are almost worthless to the microscopist until the
extraneous matter is removed from them;  and this is frequently
difficult in the extreme to perform satisfactorily.  As an instance,
certain  Foraminifera may be mentioned in which the cells  are
placed  "one  upon another,  consequently  the object must be
reduced to  a certain  degree of  thinness before a single uniform
layer of these cells can be .obtained to show something of the inter-
nal arrangements.
   Most animal and vegetable forms require an examination of the
separate parts before much can be known about them.  The mass
must be divided into separate portions, each part intended to be
preserved being cleaned from the useless matter with Avhich it is
surrounded.  It will  frequently be found necessary to make thin
sections, which from a very tender  substance is  no easy matter;
and much patience will be necessary to attain anything like pro-
ficiency.
   This making of sections was not until very recently entered into
by many except those belonging to the medical profession, but I
do not see why this  should be so, as much may be accomplished
by a persevering and interested mind Avhere there is time for enter-
ing into the subject.  I will therefore make  an attempt  to give
some instructions on this subject also.   We will first  consider the
cutting of sections from hard substances, in which the ordinary
knife, chisel, &c, are of  no avail.  Most of these require no par-
ticular care  in mounting, but  are placed in balsam like the other
objects noticed in Chapter III.: where, hoAvever, any special treat-
ment is necessary it  will be commented upon as we proceed.
   Shells, &c.—It is seldom, if ever, necessary to possess apparatus 
OF MICROSCOPIC OBJECTS.
93
for this process except a small thin saw made with a steel  blade,
for which a piece of watch-spring serves very well; a fine stone
such as is used for sharpening pen-knives; and two smooth lea-
ther strops, one of which is to be used with putty-powder to polish
the section after grinding, and the other dry, to give the final sur-
face.   It is, however, very convenient to have three or four files
of different degrees of fineness.   The shell, if  very thick, may be
divided by using the watch-spring saAv ;  and this section may then
with ordinary care  be rubbed down with water on the  stone until
one side of it is perfectly flat.  When this is accomplished it must
be again rubbed with putty-poAvder upon the strop, and  finally
upon the other strop without the powder.  This surface will then
be finished and must be firmly united to the slide in the position
it is intended to occupy.   To do this a small quantity  of Canada
balsam may be dropped upon  the middle of the slide and heated
over the lamp until on cooling it becomes hard; but this must be
stopped before it is rendered brittle.  Upon this the polished sur-
face must be laid, and sufficient  heat  applied to allow the object
to fall  closely upon  the slide,  when slight pressure may be used
to force aside  all bubbles,  &c.   On cooling, the adherence will be
complete enough to allow the same grinding and polishing upon
the upper surface which the lower received.  Whilst undergoing
this, the section must be examined from time to time to ascertain
whether the necessary degree of thinness has been reached.   When
this is  the case the section should be washed thoroughly and dried.
It must then be  covered, which is best done by using the ordinary
Canada balsam, as recommended in Chapter III.
   Sections of some exquisitely beautiful objects are cut  with much
less trouble than the above.   The Orbitolite, for' instance, may be
prepared in  this manner.   Take the object and by pressure with
the finger rub the side upon a flat and smooth  sharpening stone
with water until the portion is  reached which it is wished to shoAv.
The strength of the object will easily alloAv this to be accomplished
with ordinary care.  This side may then be attached to the glass
slide with .heated balsam,  as above  described, and the object may
then be gently rubbed doAvn to the degree of thinness required to
show it to the best advantage.   After removing  all  disengaged
matter from the object by washing and thoroughly drying, it may 
94               PREPARATION AND MOUNTING

be mounted in balsam in the usual manner, Avhen it is equally
beautiful as a transparent or opaque object.  From this it will be
seen that in  many instances where a smooth stone is found suffi-
cient  for the  work (Avhich is often the  case when the  section is
mounted in balsam) the final process of  polishing advised above
may be dispensed with, as  in the Orbitolite, Nummulite, &c,  &c.
It is quite necessary that the stones on which the objects are rub-
bed be perfectly flat, otherwise one side must be acted upon before
the other, and it will be found impossible to attain anything like
uniformity.   Where it is not practicable to cut a section and the
object is very thick, a coarse stone may be first  used to  reduce it
and the smoother afterwards.
  The consideration of the cutting of sections from  shells would
scarcely be deemed complete without some mention of what  Dr.
Carpenter terms the decalcifying process.   Muriatic acid is diluted
with twenty times its volume of water, and in this the shell is im-
mersed.  After a  period, differing according to the thickness of
the shell, the carbonate of lime will be dissolved away, and a pecu-
liar membrane left, showing the  structure of the shell very per-
fectly.  This  may be  mounted dry, in  balsam,  or  sometimes in
liquid, according to the appearance of the  object; but no rule  can
be given.   The discretion of the student, however, will enable him
to choose the most suitable method.
  From some shells it is easy to divide thin plates, or " laminae,"
which require nothing but  mounting in Canada balsam to  show
the texture very well.  In  working, hoAvever, with  those which
are " pearly," it Avill  be found that experience and patience are
needed, as  they are very brittle  and peculiarly hard; but a little
practice will overcome these  difficulties.
  Amongst the Echinodermata, which include the star-fishes, sea-
hedgehogs, &c, there are many  whose  outer surface is  covered
with " spines," or thin projections. Some of these are sharp and
thorn-like,  others blunt, longer or shorter, and, indeed, of endless
variety.  In  many of these, when a section  is made, rings  are
seen  which have a common centre, with radiating  supports, re-
sembling sections of some, of the  woods.   These are very beauti-
ful  objects, and methods  of procuring them may  now  be  con-
sidered.  It is the best to cut as  thin a section as can safely  be 
OF MICROSCOPIC OBJECTS.
95
got with the watch-spring saw first, when the smooth " sharpening
stone " may be used to polish one side, which is easily accomplished
with water only.   When this is effected, it must be Avashed clean,
and thoroughly dried, and then may be united to the slide in the
same manner as before recommended for the  Orbitolite, &c.   If
it is ever  necessary to displace it on account of inequalities,  bub-
bles, or other remediable  fault, this may be done by warming the
slide;  though too  much  heat must be avoided, otherwise fresh
bubbles will certainly be produced.  The covering with thin glass,
balsam, &c, will present no difficulty to the student;  but he must
remember that the transparency is somewhat increased by this
last operation.
   Corah are often treated in this way, in order to  reveal  their
structure.  Except, however,  the  student has had much  practice,
he  will often find this a most difficult  task, as many of  them are
exceedingly  brittle.  He will find the method before described
equally applicable here, and should take both horizontal and verti-
cal sections.
   Coal.—This substance is one of the  most interesting objects to
the microscopist.  It is, of  course, of a vegetable  origin; and
though this  is in many cases of  such minute separate portions as
to have lost all appearance of vegetation, yet it is very frequently
met Avith in masses, bearing  the  form, even to the minute mark-
ings, of Avood, in various directions.  To see this and  prepare it
for microscopic research, a suitable piece of coal must be obtained;
but in every case  the  cutting and  preparation of these sections
require great care and skill.  Sometimes  the  coal is first made
 smooth on one side, fastened to the glass, reduced to the requisite
 degree of thinness, and finished in  the method before described.
 This mode of treating it is sometimes, hoAvever, very tantalizing,
 as, at  the last moment, Avhen the section is about thin enough, it
 often  breaks up,  and  so renders the  trouble bestoAved upon it
 fruitless.   The  dark colour  and opacity of coal render an extra-
 ordinary thinness  necessary,  and so increase  the  liability to this
 accident.
   Perhaps the best method which can be  pursued is that recom-
 mended in the " Micrographic Dictionary," which is as follows :—
 " The coal is macerated for about a week in a solution of carbonate 
96
PREPARATION AND MOUNTING
of potash ; at the end of that time it is possible to cut tolerably
thin slices with a razor.  These slices are then placed in a watch-
glass with strong nitric acid, covered  and gently heated; they
soon turn brownish, then  yellow, Avhen the process must be ar-
rested by dropping the Avhole into a saucer of cold water, else the
coal would be dissolved.    The  slices  thus  treated appear of a
darkish amber colour, very transparent, and exhibit the structure,
when existing, most clearly.   We have  obtained longitudinal
and transverse sections of coniferous wood from various coals in
this way.  The specimens are best preserved in glycerine in cells;
we find that spirit renders them opaque, and  even  Canada balsam
has the same  defect.   Schulz states that he has brought out the
cellulose reaction with iodine, in  coal treated with nitric acid and
chlorate of potash."
   Cannel-coal is so close and firm in its structure as to be much
used instead of jet in  the  manufacture of  ornaments; it  takes a
beautiful polish, and consequently presents the student Avith none
but ordinary difficulties in  getting sections  of it.   Its formation is
somewhat different from that of coal, sometimes showing the transi-
tion very clearly.
   In flint there  are  often found remains  of sponges, shell, Dia-
tomaceae, &c.; but to  show these well, sections must be cut and
polished by the lathe and wheel of the lapidary, which the micro-
scopic student seldom possesses.   Thin chippings may, however,
be made, which when steeped in turpentine  and mounted in bal-
sam, will frequently show these remains very well.
   Teeth are  very interesting objects  to  all microscopists, more
especially to those who give much  study  to them; as the class
of animal may very frequently  be known from one solitary re-
maining tooth.   To examine them thoroughly, it is necessary to
cut sections of them ;  but  this is rather difficult to  perform well,
and needs some  experience.  Some  instructions, hoAvever, will at
least lessen these difficulties, and we will now endeavour to  give
them.
   It is  generally thought that  Canada balsam injures the finer
markings of these sections, consequently they are almost invariably
mounted dry.  A thin piece is first cut from the tooth with the
saw of watch-spring before mentioned, if possible ; but should the 
OF MICROSCOPIC OBJECTS.
97
substance be too hard for this, the Avheel and lathe must be used
with diamond dust.  If this cannot be procured, there is no alter-
native but to rub down the Avhole substance as thin as practica-
ble on some coarse stone or file.   The surface will then be rough ;
but this may be much reduced by rubbing upon a flat sharpening
stone Avith the finger, or a small piece of gutta-percha, upon the
object to keep it in contact.  The scratches may be much lessened
by this, but not so thoroughly removed as microscopic examina-
tion requires in dry sections.  It must, therefore, be polished with
the putty-powder and dry strop,  as recommended in the working
of the shell-sections.  The other side of the section of the tooth
may then be rubbed  down to the requisite thinness, and polished
in the same manner,  when the dust and other impurities must be
removed by washing, after which the  section must be  carefully
dried and mounted.  Some of these sections are  equally interest-
ing as opaque or transparent objects.
  The dentine of the teeth may be calcified by submersion of the
section  in dilute muriatic acid; after drying and  mounting in
Canada balsam it presents a new and interesting appearance,
showing the enamel fibres very beautifully when magnified about
three hundred  diameters.  A friend  tells me that after submer-
sion of the whole tooth in the acid he has been able to cut sections
with a razor.
  Sections of Bone.—With the aid of the microscope few frag-
mentary remains have proved so  useful to the geologist and stu-
dents of the fossil kingdom as  these.  From a single specimen
many of our naturalists can tell Avith certainty to what class of
animal it has once belonged.  To arrive at this point of knowledge
much study is necessary, and sections of various kinds should be
cut in such a manner as will best exhibit the peculiarities of forma-
tion.  The methods of accomplishing this will now be considered.
It may, however, be first mentioned that the chippings of some
bones will be found useful now  and then, as before stated with
flint, though this is by no means a satisfactory way of proceeding.
Sometimes the bones may be procured naturally so thin that they
may be  examined without any cutting ;  and only require mount-
ing dry or in fluid, as may be found the best.
  When commencing  operations Ave must provide  the same ap- 
98
PREPARATION AND  MOUNTING
paratus as is needed in cutting sections of teeth, before described.
A fine saw, like those  used for cutting brass, &c.;  two or three
flat files of different degrees of coarseness ; two flat " sharpening "
stones;  and a leather strop with putty-poAvder for polishing.  As
thin a section as possible  should  first be cut from the part re-
quired by the aid of the fine saw  ; and it is better Avhen in  this
state  to soak it for some short time in camphene, ether, or some
other spirit to free it from  all grease.   With the aid of a file we
may now reduce it almost to the necessary degree of thinness, and
proceed as before recommended with teeth.   The " sharpening "
stone will remove all  scratches and marks sufficiently to allow  it
to  be examined with the microscope  to see if it is ground  thin
enough;  and if it is  to be mounted dry we must  polish it Avith
putty-powder and water upon the strop to as high a degree as
possible, and having washed all remains of polishing powder,  &c,
from the  section we must place it upon the slide and  finish  it as
described in  Chapter  II.
   If the bone is not sufficiently hard in its nature to bear the above
method of handling whilst grinding and polishing—as some are
far more brittle than  others—as thin a section  as  possible must
first be cut with the saAv, and one surface  ground  and polished.
The  piece must then be dried and united to the glass by heated
balsam in the same manner as shells, &c.  After which the super-
abundance of balsam must be removed from the glass;  then rub
down upon the  stone and strop as before.  When the polishing is
completed the whole slide must be immersed in chloroform, ether,
or  some other  spirit,  to release  and cleanse the section, when  it
may  be mounted as the one above mentioned.
   Some have recommended a strong solution of isinglass to affix
the half-ground teeth or bones to the glass as causing them  to
adhere very'firmly and requiring  no heat, and also being readily
detached when finished.
   The  reason Avhy the sections of bone are usually mounted dry
is that the " lacuna?" bone cells, and canaliculi (resembling minute
 canals) shoAv their forms, &c, very perfectly in this state, as they
 are holloAv and contain air, Avhereas  if they become filled  with
 liquid  or balsam—Avhich  does sometimes  occur—they become
 almost indistinguishable.  There are some dark specimens, however, 
OF MICROSCOPIC OBJECTS.
99
 where the cells are already filled with other matter, and it is well
 to mount these with balsam and so gain a greater degree  of trans-
 parency.
   To gain a true knowledge of the structure of bone, sections must
 be cut as in wood, both transversely and longitudinally; but Avith
fossil bones, Avithout the lapidary's wheel, &c, it is  a laborious
 task, and indeed can seldom be properly accomplished.  In this
 place, also, it may be mentioned that by submitting  bone to the
 action of muriatic acid diluted ten or fifteen times with water, the
 lime, &c, is  dissolved away and the cartilage is  left, which may
 be cut  into sections: in caustic potash the animal matter is got
 rid of.   Both of these preparations may be mounted in fluid.
   The  method  of cutting thin  sections of bone may be  also em-
 ployed Avith the stones of fruit, vegetable ivory, and such  like sub-
 stances ;  many of which show a most interesting arrangement of
 cells, especially  when the sections are transverse.   Most  of these
 objects present  a different appearance  when mounted dry to that
 which they bear when in balsam, owing to  the cells becoming fill-
 ed ; and to arrive at  a true knowledge of  them we must have a
 specimen mounted in both ways.
   To those who study polarized light, few objects are more beau-
 tiful than the sections of the different kinds of  horn.   We will
 briefly  inquire into the best  method  of  cutting these.  There are
 three kinds of horn, the first of Avhich is hard, as the stag's, and
 must be cut in  the same manner  as  bone.   The  second  is some-
 what softer, as  the cow's.   The  third is another and still softer
 formation, as the  " horn" (as it is termed)  of the rhinoceros.  In
 cutting sections of the two last we should succeed best  by using
 the machine invented for these  purposes  Avhich I shall shortly de-
 scribe when the method of cutting wood is  considered.   To aid
 us in this Avhen the horn is hard it must be boiled for a short time
 in water, Avhen the cutting will be more easily accomplished.  The
 sections  should be both transverse and longitudinal, those of the
 former often shoAving cells Avith beautiful crosses,  the colours Avith
 the selenite plate being truly splendid.   Of this class the rhino-
 ceros horn is one of the best;  but the buffalo also affords a very
 handsome object.  The cow's, and indeed almost every different
 kind of horn, well deserves the trouble  of mounting.   Whalebone, 
100
PREPARATION AND MOUNTING
when cut  transversely, strongly resembles those of the third and
softer formation.  All these are best seen Avhen mounted in Canada
balsam, but care  must be taken that they have been thoroughly
dried after cutting, and then steeped in turpentine.
  An interesting object may also be procured from whalebone by
cutting long sections of the hairs of which it is composed.  Down
the centre of each hair we shall find a line of cells divided from
one another very distinctly.   And  (as recommended in the " Mi-
crographic Dictionary ") if whalebone be macerated twenty-four
hours in a solution of caustic potash it will be softened, and by
afterwards digesting in water,  the outer part will be resolved into
numerous  transparent cells, which  will show  more plainly the
structure of this curious substance.
  In a former chapter, hairs were mentioned, their many and in-
teresting forms, and their beauty Avhen used with polarized  light.
The sections of them, however,  are no  less a matter of study, as
this  mode of treatment opens to sight  the outer  " casing," and
the inner  substance somewhat resembling the pith of plants.
  It would be  out of place to enter into the description of the
different forms met with ; but the  ways in which sections are to
be procured may be glanced at. If transverse sections are required,
some place a quantity of hairs betwixt  two flat pieces of cork,
Avhich by pressure hold them  firmly enough together to allow the
required portions to  be cut Avith a razor.  Others take a bundle
of the hairs and dip it into gum or glue, Avhich gives it Avhen dry
a solidity equal to wood.  Sections of this are then cut  Avith the
machine mentioned a little further on, and these may be mounted
in balsam.  The human hair is easily procured in the desired sec-
tions by shaving as closely as possible a  second time and cleansing
from the lather, <fec, by carefully washing.  Most hairs, however,
should  be examined both transversely  and longitudinally.   It is
not difficult to  procure the latter, as we may generally split them
with the  aid of a sharp razor.  In  a great number of  hairs there
is a quantity of greasy matter Avhich must be got rid of by soak-
ing in ether or some other solvent before mounting.
   We may next consider the best method of procuring sections of
wood, Avhich  must be cut of such a degree of thinness as to form
transparent objects, and so display all  the secrets of their struc- 
OF MICROSCOPIC  OBJECTS.
101
ture.  There is no  monotony in this study, as the forms are so
various, and  the arrangement of the cells and woody fibre so dif-
ferent, that the microscopist may find endless amusement or study
in it.   From a single section the class of trees to which it has be-
longed may be known, often even when the wood is fossil.  The
apparatus best adapted for cutting these sections is made as fol-
lows :—A flat piece of hard  wood,  about  six inches long,  four
wide,  and one thick, is chosen, to which another of the same size
is firmly fixed, as as to form in  a side view, the letter T.   On
one end  of the upper  surface is  fastened a brass plate, perfectly
flat, in the centre of which a circular opening is cut about half an
inch in diameter.  Coinciding Avith this opening is a brass tube,
fixed in the under side of the table (if it may be termed so).  This
tube is so cut at the  bottom as to take a fine screw.   Another
screw is also placed at the same end of the  " table," which works
at right angles to this, so that any substance in the tube  may be
wedged firmly by working this last  screw.  To use this  instru-
ment, the piece of wood or other object of Avhich a section is re-
quired must  be placed in the  tube, when,  by  turning  the screw
underneath, the wood is raised above the brass plate more or less
as wished, and by using the screw at the end, it is held firmly in
the same position.  With a flat  chisel the  portion of the object
Avhich projects above the surface of  the brass  plate may now  be
cut off, and by means  of the bottom screw another portion  may
be raised and treated in the same manner.  As to the thickness
of which objects should be cut, no proper directions can be given,
as this differs so greatly that nothing but experience can  be any
guide.  The same thickness can be obtained by working the screw
underneath  in uniform degrees, the head being marked for this
purpose ;  and Avhen the substance to be cut is very much smaller
than the hole in the brass plate, it may be wedged with cork.
   As this  instrument is peculiarly adapted  for  cutting wood
(though  used for other substances, as before mentioned), I  shall
notice a  few particulars  concerning  this branch of sections.  It
may here be remarked, that to obtain anything like a true know-
ledo-e of the nature of  wood,  it should be cut and examined  in at
least two directions, across and along.   The piece of wood is often
placed in spirits for a day or  two, so that all resinous matter may 
102
PREPARATION AND  MOUNTING
be  dissolved out of it;  it must  then be soaked in water for the
same length of  time, so as to soften and  render it easy to  cut.
Sections are obtained in the manner described above, but often
curl to such a degree as to make it necessary to immerse them in
water, from which they may be taken and dried under slight pres-
sure.  They are often mounted  dry, and require no care  beyond
other objects, as in Chapter II.   Some, however, are best mounted
in balsam,  particularly the long sections when used for the pola-
riscope ; these  must be soaked in  turpentine, and the  greatest
care taken  that all air bubbles are got rid of.   Others are thought
to be most useful Avhen mounted in shallow cells with some of the
preservative liquids mentioned in Chapter IV.—weak spirit  and
water, chloride of calcium solution of the strength of one part of
the salt to  three parts of distilled water, &c.
   The above "section-cutter" may  not  be within  the reach of
every student, nor is it absolutely necessary; though where any
great number of  specimens is required it is very useful, and insures
greater uniformity in the thickness.   Many employ a razor for the
purpose, which must  always be kept sharp by frequent stropping.
Sections of leaves also may be procured by the  same means,
though, as  before mentioned, they are sometimes easily  divided
by stripping the coatings off with the fingers.  The cells Avhich
come to  sight by cutting some of the orchideous plants are most
interesting.  To cut  these leaves they may be laid upon a flat
piece of  cork, thus exposing the razor to no danger of injury by
coming in  contact with  the support.  It may be  mentioned here
that the razor may  also be used in  cutting sections of the rush,
than which a more beautiful object  can scarcely be found when
viewed  transversely, as it shows the stellate arrangements of the
ducts to convey the liquids to the different parts of the plants very
clearly.   This should be mounted dry.  In the same way sections
of the leaf-stalks of ferns may also be cut, some of which, as Dr.
Carpenter states, show the curious ducts very beautifully, especially
when cut rather obliquely.
   When sections of  the softer substances are required, no instru-
ment can be compared with " Valentin's knife," which consists of
two steel blades lying parallel with  one  another and attached at
the lower end.   The  distance of separation may be regulated at 
OF MICROSCOPIC OBJECTS.
103
will by a small screw near the handle.  When,  therefore,  a sec-
tion is Avanted, the substance must be cut through, and  betwixt
the blades a thin strip -will be found, which may be made of any
thickness,  according to the distance of  their  separation.  By
loosening the screw the blades may be extended, and  the section
may be floated out in Avater if  the  damp will  not injure it.   The
knife  cuts much better if dipped in water immediately before use
and also when the substance to be operated  upon is Avet, or even
under Avater altogether ; but care must be taken, after use, to clean
the blades thoroughly and oil them before laying by, if the place
is at  all damp.  This instrument is most  useful in such  subjects
as anatomical preparations Avhere the sections are required to show
the position of the different vessels, &c.; but, as before stated,
is very valuable for all soft substances.  As an instance of this, it
may  be mentioned, that it is frequently used in cutting  sections
of sponges;  but as these  are often very full of spicula, &c, it is
much better to press  the  sponge flat  until dry, and then cut off
thin shavings with a very sharp knife ; these shavings will expand
when placed in water.  After this they may be laid betwixt two
flat surfaces and dried, when they may be mounted as other dry
objects, or, when desirable, in balsam.
   Valentin's  knife is very much used in taking  sections of skin,
which are aftenvards treated with potash  solution, acids, &c, to
bring out in the best Avay  the different  portions.  Dr. Lister's
mode, however, of getting these is thus given in the  Microscopic
Journal:—" But  I  aftenvards found  that much better  sections
could be obtained from dried specimens.   A portion of shaved
scalp being  placed between two  thin  slips  of deal, a  piece  of
string is tied round them so  as to exercise  a slight degree of com-
pression ; the preparation  is now laid  aside for twenty-four  hours,
when it is found to be dried to an almost horny  condition.   It
then  adheres  firmly by its lower surface  to one  of  the slips, and
thus  it can be  held securely,  while  extremely thin and equable
sections are cut with  great facility in any  plane that  may be
desired.   These sections,  when moistened with a drop of water
and  treated with acetic acid, are as Avell suited for the investiga-
tion  of the muscular tissue as if they had not been dried."
   There are many who almost confine their attention  to polarized 
104
PREPARATION  AND MOUNTING
light and its beautiful effects.   Such would not deem these efforts
to aid the  student  in  cutting  sections  complete Avithout  some
notice  of those Avhich are taken from  various crystals, in order to
display that curious and beautiful  phenomenon,  the rings with a
cross.  The arrangement of these is someAvhat  changed by the
crystal which  affords the section ; but nitrate of potash gives two
sets of rings with a  cross, the long line of which passes through
both, the short line dividing it in the middle.
  The process of cutting these  sections is rather difficult, but a
little care and perseverance will conquer all this.  The following
is extracted from the Encyclopaedia Metropolitans:—" Nitre crys-
tallizes in long six-sided prisms whose section, perpendicular to
their sides, is  the regular hexagon.   They are generally very much
interrupted in their  structure ; but by  turning over a considera-
ble quantity of the  ordinary saltpetre* of the shops  specimens
are readily  found which have  perfectly transparent portions of
some extent.   Selecting  one of these, cut it with a knife  into a
plate above a  quarter of an inch thick,  directly across the axis of
the prism,  and then grind it down  on a broad  wet file  till it is
reduced to about one quarter or a sixth of an inch thick, smooth
the surface on a wet piece of emeried glass, and polish on a piece
of silk strained very tight over a strip of plate-glass, and rubbed
with a mixture  of tallow and colcothar of vitriol.  This operation
requires practice.  It cannot be effected unless the nitre be applied
wet and rubbed till quite dry, increasing the rapidity of the fric-
tion as the moisture evaporates.  It must be performed in gloves,
as the vapour  from the fingers, as well as  the slightest breath,
dims the polished surface effectually.  With these  precautions  a
perfect vitreous polish  is easily obtained.  We may here remark,
that hardly any two salts  can be polished by the same process.
Thus,  Rochelle-salt must be finished wet on the silk, and instantly
transferred to soft bibulous linen and rapidly rubbed dry.  Experi-
ence alone can teach  these peculiarities, and it is necessary to
resort to contrivances  (sometimes very strange ones) for the pur-
  * Sometimes the saltpetre of the shops is nitrate of soda, and  as this is
slightly deliquescent, it is well to be certain that we have the nitrate of potash,
which is free from this defect. 
OF MICROSCOPIC OBJECTS.
105
pose of obtaining good polished sections of soft crystals, especially
of those easily soluble in water.
  " The  nitre is thus polished on both its surfaces, Avhich should
be brought as near as possible to parallelism."
  Some  sections of  the naturally formed crystals also  show the
" rings"  very well,—as Iceland Spar, which gives a single ring
and  cross;  but  the  difficulty of cutting and polishing them  is
almost too  great for the  amateur,  and must be left to  the lapi-
dary.  This curious  phenomenon, however, may be seen by using
a plate of ice uninterruptedly formed of about one inch in thick-
ness.
   Before concluding these remarks on  sections, I must mention
a  feAV difficulties Avhich may be met Avith,  and their  remedies.
The foremost of these  is the softness  of some objects, which have
not  resistance enough  in themselves to bear cutting  even Avith the
sharpest instruments.   This may often be removed by soaking in
a solution of gum,  and then drying, which will  render the sub-
stance firm enough  to be cut, when the  sections must be steeped
in water, and the gum thus got rid of.   Small seeds, <fcc, may be
placed in Avax Avhen  Avarmed, and will be held firmly enough when
it is again cold to  allow of them being cut  into  sections, &c.
And,  lastly, where  a  substitute for a microscopist's hand-vice is
required, a  cork Avhich fits any tube large enough may  be taken
 and split, the object  being then placed between the two parts,
and the  cork thrust into  the tube,  a  sufficient degree of firmness
 will be obtained to  resist any necessary  cutting, &c.
   Dissection.—As I stated at the commencement of this chapter,
no written instructions can enable any student to become an adept
 in this branch  without much experience and no little study.   I
 will, however, describe the necessary apparatus, and afterwards
 mention the mode of treatment which certain objects require.
   A different microscope  is manufactured for the purpose of dis-
 section, most first-rate makers having their own  model.  The
 object-glasses of many of these are simple, and  consequently not
 expensive ; but one of the great requisites is a stage large enough
 to hold the trough, in which  the operation is  often performed.
 Where this is the case it Avould scarcely be  worth the  expense of
 getting a dissecting microscope if the student  were pursuing no 
106
PREPARATION AND  MOUNTING
particular study, but merely made use of the instrument when an
object to be operated upon turned up accidentally.   The ordinary
form is much  improved for this  purpose, by having tAvo  Avooden
rests placed at the sides of the microscope, upon Avhich the hands
may be supported when working upon the stage.   These should
be weighty enough to be free from danger of moving.  These sup-
ports will also be found to be a remedy against much of the weari-
ness which inevitably  arises from having to sustain the hands as
well as work with them.   The  erector,  as I before observed, is
necessary to a young student; but  Avith a little practice he may
work very well without it.
  We will now notice some of the instruments Avhich are most
useful in dissection.  Tavo or three different sizes of ordinary scis-
sors should be possessed, but the  shapes must be modified in
others for many purposes, as those used by surgeons : a pair with
the cutting parts bent  in a horizontal direction, and another pair
slightly curved in a perpendicular ; so that parts of the substance
operated upon may be reached, which it would be impossible to
touch  Avith straight  scissors.  One  point of these is  sometimes
blunt, and the other acute, being thus  made very useful in open-
ing tubular  formations.  Another form of these is made, where
the blades of the scissors are kept open by a spring, the  handles
being pressed together  by the fingers.   Where it is desirable, one
or both of these handles may be  lengthened to any degree by  the
addition of small pieces of wood.
  The Knives which  are most  useful are those of the smallest
kind which surgeons employ in very delicate operations.   These
are  made about the length of an ordinary penknife, and are fixed
in rather long  flatfish handles ; some are curved inAvards, like  the
blade of a scythe,  others  backAvards; some taper to a point,
whilst others again are broad and very much rounded.   Complete
boxes are now fitted up  by the  cutlers, of excellent quality and
surprisingly cheap.
  Needles.—These are very useful, and should be  firmly fixed in
handles as recommended in  Chapter I.  It is convenient to have
them of various  lengths  and thicknesses.   If curved by heating
and bending to any required shape they may be re-hardened  by
dutting them  Avhilst hot into cold  water.   Dr. Carpenter also 
OF MICROSCOPIC OBJECTS.
107
 makes edged instruments by  rubbing doAvn needles upon a hone.
 They are more pleasant to Avork Avith when short, as  the spring
 they have Avhilst long robs them of much of their firmness.
   A glass syringe is also useful in many operations, serving not
 only to  cleanse the objects but to add or Avithdraw liquids  from
 the dissecting-trough.  This trough will now be described, as many
 substances are so changed by becoming dry that it is  impossible
 to dissect them unless they  are immersed in Avater  during the
 operation.  If the object is opaque and must be Avorked by reflect-
 ed light, a small  square trough  may be made  to the required size
 of gutta-percha, Avhich substance will not injure the edge of the
 knives, &c.; but where transparency is necessary, a piece of thin
 plate-glass must be taken, and by the aid of  marine glue (as ex-
 plained in Ghapter  IV.) the  sides  affixed of  the required depth.
 As pins, &c, cannot be used  with the glass troughs and the sub-
 stance must be kept extended,  a thin sheet of cork loaded  Avith
 lead in order to keep it under  water may be used; but this, of
 course, renders the bottom opaque.   When  Avorking Avith many
 thin substances, a plate of glass  three or four inches long and two
 wide Avill  serve every purpose,  and be more pleasant to use  than
 the trough.  A drop or tAvo of  Avater will be  as much liquid as is
 needed, and this will lie very Avell upon the flat surface.   As these
 arc the principal  apparatus and  arrangements  Avhich are requisite
 in dissection, the method of proceeding in a few cases  may  now
 be noticed.              '
   Vegetables.—The dissection of vegetable  matter is much less
 complicated than  that of animal;  maceration in Avater being  a
 great assistant, and in many  cases removing all necessity for the
 use of the knife.  This maceration may be assisted by needles, and
 portions of the matter Avhich are not required  may be removed by
 them.  When, for instance, the spiral vessels which are found in
 rhubarb  are Avanted, some parts  containing these are chosen and
 left in a small quantity of water until the mass becomes soft, and
 this is more quickly effected Avhen the Avater is not changed.   The
mass must be  then placed upon  a glass plate Avhen practicable, or
in the  trough Avhen large, and  a\ ith  the aid  of  tAvo needles  the
matter may be removed from the spiral vessels, Avhich are plainly
seen  Avith a comparatively Ioav  poAver; and by comyeying these 
108
PREPARATION AND MOUNTING
to a clean slip of glass, repeating the process, and at last AA'ashing
well, good specimens may be procured.  Most of these should be
mounted in some of the preservative liquids in the manner described
in Chapter  IV.  Many, hoAvever, may be  dried on the  slide, im-
mersed in turpentine, and then mounted in balsam ; but liquid is
preferable, as it best preserves the natural appearance.  Certain
kinds of vegetables require a different treatment to separate these
spiral  vessels.   Asparagus is composed of very  hard  vegetable
matter, and some have  recommended the stems to be first boiled,
Avhich will soften them to such  a degree that they may easily be
separated.   Dilute  acids are also occasionally used to effect  this;
and in some instances to obtain the raphides caustic potash may
be  employed;  but  after any of  these agents have been made use
of,  the objects  must be thoroughly cleansed Avith Avater, else the
dissecting instruments  (and perhaps the cell) Avill  be  injured by
the action of the remaining portion of the  softening agent.
   For the  dissection  of animal tissues it is necessary that the
instruments be in the  best order as to sharpness, Arc.;  and as the
rules to be observed must  necessarily be someAvhat alike in many
instances, the treatment required by some of the objects  most
frequently mounted will noAV be described.   We may here remark
that cartilage can be best examined by taking sections,  Avhich will
show the arrangement of the cells very perfectly.   This, however,
is  plainly seen in  the  mouse's ear  Avithout  any  section being
necessary.  Glycerine,  the preservative* liquids before mentioned,
and Canada balsam are all used to mount it; but perhaps the
first named may be  preferred in many cases.
   Muscle.—This is Avhat is commonly called the " flesh " of ani-
mals.   If a piece be  laid upon the  slide under the microscope,
bundles of  " fibres " Avill be perceived, Avhich with needles and  a
little patience may be  separated into  portions, some of these being
" striated," or  marked  Avith alternate spaces  of  dark  and  light.
Some of the non-striated or smooth class of muscle, such as is found
in  intestines, may be prepared for the microscope  by immersing
for a day or two in nitric acid diluted Avith three or four  parts of
Avater, and  then separating with needles and mounting as  soon  as
possible.   Sometimes boiling is resorted to to facilitate the sepa-
ration, and  occasions little or no alteration  in the material.   Speci- 
OF MICROSCOPIC OBJECTS.
109
mens are often taken from the frog and the pig, as being amongst
the best, Goadbfs solution being generally used in mounting them.
The  muscle of insects also shows the striae  very perfectly.
   Nerve-tissue.—This  is seldom mounted;  as Dr.  Carpenter
observes,  " no method of preserving  the nerve-tissue has  been
devised Avhich makes it Avorth Avhile to mount preparations for the
sake of  displaying its minute characters," but Ave will mention a
few particulars to be observed in its treatment.   The nerve should
be taken from the animal as  soon as possible after death, and laid
upon a glass slide, Avith a drop or two  of serum if possible.  The
needles may be used to clean it, but extreme  delicacy is necessary.
It will be found that the nerve is tubular and filled Avith  a substance
Avhich is readily ejected by very slight pressure.   When the nerve
is submitted to the action of acetic acid, the outer covering, which
is A-ery thin, is  considerably contracted, Avhilst  the  inner tube is
left  projecting; and thus is most distinctly shown  the nature of
the  arrangement.   Mr.  Lockhart  Clarke, Avho has made  great
researches into the structure of the spinal cord, gives a part of his
experience as  folloAvs:—He takes a perfectly  fresh spinal cord and
submits it to the action of strong spirits of Avine.  This gives the
substance  such a degree of hardness  that thin sections may be
readily  cut from  it, Avhich should be  placed upon a glass in a
liquid  consisting of three parts of spirit and one of acetic acid,
Avhich renders them very distinct.   To mount these  sections, they
must now be steeped  in pure spirit for tAvo hours and aftenvards
in oil of turpentine, and lastly must be  mounted in Canada balsam.
   Tracheae of  Insects.—The nature of  these Avas described in
Chapter III., but the method of procuring them Avas not explained,
as this  clearly belongs  to  "dissection."   The  larger tubes are
readily  separated by  placing the  insect  in  Avater, and fixing as
firmly as possible, Avhen  the body must be opened and the viscera
removed.  The tracheae may then be cleaned  by the aid of a camel-
hair pencil, and floated upon a glass, Avhere they must first be
allowed  to dry, and then  be mounted in balsam.  Mr.  Quekett
gives the  folloAving method of removing the tracheae from the
larva of an insect;—"  Make a small opening  in its body, and then
place it  in strong acetic acid.   This will soften or decompose all
the  viscera, and the tracheae may then be well washed with the 
110
PREPARATION and  mounting
syringe, and removed from the body Avith the greatest facility, by
cutting aAvay the connections of the main tubes with the spiracles
by means of fine-pointed scissors.   In order to get them upon the
slide, it must be put into  the fluid, and the tracheae floated upon
it;  after  Avhich they may be  laid out in their proper position, then
dried and mounted in  balsam."   If we wish them to bear their
natural appearance, they must be mounted in a cell with Goadby's
fluid;  but the structure  is  sometimes Avell  shown  in  specimens
mounted dry.   As before  mentioned, these tracheae terminate on
the outside in openings termed spiracles, which are round, oblong,
and  of various shapes.  Over these  are generally  a quantity of
minute hairs, forming a guard against the  entrance of dust, &c.
The forms of these are seldom alike in two different kinds of insects,
so that there  is here a Avide field for the student.  The dissection,
moreover, is very easy, as  they may be cut from the body with  a
sharp knife or scissors, and mounted in balsam or fluid.  Many of
the larvae afford good specimens, as do also some of the common
Coleopterous insects.
  Tongues, or Palates, of Molluscs.—Of the nature of these,
Dr. Carpenter gives the following description :—" The organ which
is  commonly  known under  this   designation is one  of a  very
singular nature ;  and we should be altogether Avrong in  conceiving
of it as having any likeness to that on Avhich our ordinary ideas of
such  an organ are founded.  For, instead of being a  projecting
body, lying in the cavity  of the  mouth, it is a tube that passes
backwards and doAvnwards beneath the mouth, its higher end being
closed, Avhilst  in front it opens  obliquely upon  the floor of the
mouth, being, as it  were,  slit up and spread out so as to form a
nearly flat surface.   On the interior of the tube, as Avell as on the
flat expansion of it, we  find numerous transverse rows of minute
teeth, Avhich are set  upon flattened plates; each principal tooth
sometimes having a basal plate of its oavii, Avhilst in other instances
one plate carries several teeth."   These palates, or tongues, differ
much amongst the Gasteropods in form  and size, some of them
being comparatively of  an immense  length.   Many are amongst
the most beautiful objects when  examined Avith polarized bVht.
They must, however, be procured by dissection, AA'hich is usually
performed as follows:—The  animal is placed on the  cork in the 
OF MICROSCOPIC OBJECTS.
Ill
dissecting-trough before mentioned, and the head and forepart cut
open, spread out, and firmly pinned down.  With the aid of fine
scissors or knife, the tongue must be then detached from its fasten-
ings, and placed in AA'ater for a day or two, when all foreign matter
may Avith a little care be  removed.   In  Avhat way it should be
mounted will depend  on the purpose for which it is intended.   If
for examination as an ordinary object, it may be laid upon the
slide and  alloAved to dry, Avhich arrangement will shoAv the  teeth
very  Avell.   If  avc wish to see it as it  is naturally, it must be
mounted in a cell Avith Goadby's fluid; but if it is Avanted as a
polarizing object, it must be  floated upon a slide, alloAved to dry
thoroughly, and then  Canada balsam added in the usual manner.
   In the stomach, also, of some of these molluscs teeth are found,
Avhich are very interesting objects to  examine, and must be dis-
sected out in the same manner as the "tongues."
   Since  writing the  above,  Dr.  Alcock (whose very beautiful
specimens prove him to be a great authority in this branch) has
published  some of his experience in  the  second volume of the
third series of " Memoirs of the Literary and  Philosophical Soci-
ety  of Manchester."   By  his permission  I  make the following
extract:—
   "This closes my present communication on the tongues of mol-
lusca; but^as  some members may possibly feel inclined to  enter
upon the inquiry themselves, I think it will not be amiss to  add a
few remarks on the manner in which they are to be obtained.
   " First,  as to the kinds best worth  the  trouble of  preparation.
Whelks,  Limpets,  and Trochuses should  be taken first.   Land
and fresh-Avatcr snails can scarcely be recommended, except as a
special study,—their tongues being rather more difficult to find,
and the teeth so  small that they  require a high  poAver to shoAv
them properly.  It would appear, from  Spallanzani's  description
 of the anatomy of the head of the snail, that even he did not make
 out this  part,  although, in his curious observations on the repro-
 duction  of lost parts, he must have carefully dissected more snails
 than any other man.
   "As to preserving the animals till Avanted, they should simply
 be dropped alive into glycerine or alcohol.  Glycerine is perhaps
 best where only the tongues  are Avanted; but it leaves the  ani- 
112
PREPARATION AND MOUNTING
mals very soft; and as it does not harden their mucus at all, they
are very slippery and difficult to Avork upon Avhen so preserved.
   " Then as to the apparatus required for dissection.  In the first
place, all  the Avork is to be done under Avater, and a common
saucer is generally the most convenient vessel to use.  No kind of
fastening  doAvn or pinning out of the animal is needed;  and, in
fact, it is much better to have it  quite free, that you  may turn it
about any Avay you Avish.   The necessary instruments are a needle-
point, a pair of fine-pointed scissors, and  small forceps ;  the for-
ceps should  have their  points slightly turned in  towards each
other.
   " A Avord or two on the lingual apparatus generally, and on its
special characters in a few different animals, will conclude Avhat I
have to say.
   "The mode of using the tongue can be easily seen in any of
the common Avater-snails, A\dien  they are  crawling on the  glass
sides of an aquarium ; it may then be observed that from between
the fleshy lips a thick mass is protruded,  Avith a motion fonvards
and upwards, and aftenvards withdraAvn, these movements being
almost continually repeated.   The action has the appearance of
licking; but when the light falls  suitably on the protruded struc-
ture, it is  seen to be armed Avith a number of bright points, which
are the lingual teeth, so arranged as to give the organ the charac-
ter and action of a rasp.
   "If you proceed  to  dissection, and  open the head of one of
these mollusca (say, for instance,  a common limpet), you  Avill find
the cavity of the mouth almost filled with the thick  fleshy mass,
the front of Avhich is  protruded in the act of feeding; and on its
upper surface, extending along the middle line from back to front,
is seen the strong membranous  band upon which  the teeth  are
set.  The mass itself consists of a cartilaginous frame, surrounded
by strong muscles; and these structures  constitute the whole of
the active part of the lingual  apparatus.....
   " But the peculiarity of the toothed membrane, Avhich makes its
name of  'ribbon' so  appropriate, is, that there is ahvays a  con-
siderable  length of it behind the mouth, perfectly formed, and
ready to come forward and supply the  place of that at the front,
Avhich is continually wearing  aAvay by use. 
OF MICROSCOPIC OBJECTS.
113
  " In the limpet this reserve-ribbon is  of great length,  being
nearly tAvice as long as the body, and the Avhole of it is  exposed
to vioAv on simply removing the foot of the animal; nothing, then,
can be easier than to extract the tongue of the common limpet.
But, unfortunately, Avhat you find in one kind of mollusc  is not at
all Avhat you find in another.   In the Acmaeas, for instance, Avhich
are  very closely related to the limpets, and have shells which can-
not be distinguished, the reserve portion of the ribbon has to be
dug out from the substance of the liver, in Avhich it is imbedded,
that organ being, as it Avere, stitched completely through by a long
loop of it.......It might be thought a comfortable reflection
that, at all events, one end of the ribbon can always be found in
the  mouth; but  in many cases this  is about the Avorst place to
look for it.   Perhaps  it may  appear  strange that in some  of the
smaller species, with a retractile trunk, a beginner may very likely
fail  altogether in his attempt to find the mouth ; if, hoAvever, the
skin of the back is removed, commencing just behind the tenta-
cles, there Avill be very little difficulty  in making out the trunk,
which either  contains the Avhole of the ribbon, as in the  whelk,
or the front part of it, as  in Purpura  and Murex, where a free
coil is also seen to hang from its hinder extremity.......In
the periwinkles the same plan of proceeding, by at once opening
the back of the animal, is best;  and on doing so, the long ribbon,
coiled up  like a Avatch-spring, cannot fail to  be found.
   "In the Trochuses, and indeed in all the Scutibranchiata, one
point of the scissors should be introduced into the mouth of  the
animal, and an incision  made  directly  backwards in  the middle
line above to  some distance behind  the tentacles;  the tongue is
then immediately brought into  vieAV, lying along the floor of  the
mouth."
   Dr. Alcock's method of dissection will  be  found to  differ in
some degree from the general rules before given; and Avhen  the
tongue is dissected out he washes it for one hour (shaking it iioav
and then) in a Aveak solution of potash.   After cleaning thorough-
ly  in Avater, it must be mounted by one of the methods before
mentioned.
   Amongst insects, especially the grasshopper tribe, are found
many which possess a gizzard, armed with strong teeth, somewhat 
114
PREPARATION AND MOUNTING
similar to those of the molluscs.  It requires great nicety of mani-
pulation to obtain these for the microscope ; but it would be use-
less to attempt any description of the process here, as the student
can only be successful by experience in dissecting objects less dif-
ficult to manage, and by using the most delicate instruments.
  We have now considered most of those objects Avhich require
any peculiar treatment in  section-cutting, &c.;  but in no branch
of microscopic manipulation is experience more necessary than in
this. 
OF MICROSCOPIC OBJECTS.               115
*
                      CHAPTER   VI.

                           INJECTION.

 1.  Injection is  the filling of the arteries, veins, or other vessels
 of animals with some coloured substance, in order that their natu-
 ral arrangement  may be made visible.  This  is, of course, a deli-
 cate  operation, and needs special apparatus, which I  will now
 attempt to describe.
   2.  Syringe.—This is usually made to contain about two ounces.
 On each side of  the part next to the  handle is a ring, so that the
 finger may be thrust  through it, and  the thumb may work the
 piston as in an ordinary syringe.   The plug of the piston must be
 " packed " with  wash-leather, and fit so closely as to be perfectly
 air-tight; and if, when it has been used awhile, it is  found that
 some of the liquid escapes past the plug into  the back part  of the
 body, it must be repacked, Avhich operation  will be best under-
 stood by examining  the part.   These syringes are made of various
 sizes, but in  ordinary operations the  above  will be  all that is
 needed.   The nozzle is about  an inch long, and polished  so accu-
 rately that there  is  no escape  when the pipes are tightly placed
 upon it dry.
   3.  The pipes are  usually about  an  inch long, to the end  of
 Avhich are affixed thicker tubes so  as  to fit the nozzle, as before
 mentioned, Avhilst a  short arm projects from  each side of these>
 so that the silk or thread which is used to tie  the artery, &c,
 upon  the thin pipe may be carried round these arms, and all dan-
 ger of slipping off prevented.  The pipes are made of different
 sizes,  from that Avhich will  admit only a very fine needle (and
 this will need now and then to be cleaned, or to be freed from
 any chance  obstruction), to  that Avhich will take  a large pin.
 These sizes must  ahvays be  at hand, as the vessels of some  sub-
jects are exceedingly minute. 
116
PREPARATION AND  MOUNTING
   4.  Stopcock.—This is a short pipe like a  small straight  tap,
which fits accurately upon the end of the syringe like the pipes,
and also takes the pipes in the same manner.  The*use of this is
absolutely necessary Avhen the object is so large that one  syringe
full of liquid will not fill  it.   If no preventive Avere used, some
part of the liquid  would  return whilst the  syringe  was being
replenished, but the stopcock is then turned as in an ordinary
tap, and all danger of this effectually removed.
   5.  Curved needles.—These are easily made by heating common
needles at the end Avhere the eye is situated,  and bending them
with a small pair of " pliers" into  a segment  of a circle half an
inch in diameter.  They are, perhaps, more convenient Avhen the
bent part is throAvn  slightly back where it commences.   The
pointed end  is then thrust into a  common  penholder, and the
needle needs no re-tempering, as the work for  which it is wanted
is simply to convey the thread or silk  under any artery or vessel
where it would be impossible  to reach  with the  unassisted
fingers.
   6. A kind of forceps,  commonly known by  the name of " bull-
nose forceps," Avill be constantly required during the process of
injecting.  These are short, usually very strong, but not heavy,
and close very tightly by their oavu spring, which may be easily
overcome and so released  by the pressure of the fingers.   When
any vessel has not been tied by the operator, and he finds the
injected fluid escaping, one of these " bulldogs" may be taken up
and closed upon the opening.  This Avill cause very  little inter-
ruption, and the stoppage will be almost  as effectual as if it were
tied.
   7 When  the ordinary  mode of  injection  is employed, it  is
necessary that the preparations be  kept warm during the time
they are used, otherwise the  gelatine or size which they contain
becomes stiff, and will not allow of  being Avorked by the syringe.
For this purpose we must procure small earthenware or tin pots of
the size required, Avhich will differ according to the kind  of work
to be done ; and to each of these a loose lid  should be  adapted
to protect it from dust, &c.  These  pots must be allowed to stand
in a tin bath of water, under which a lamp or  gas flame  may be
rdaced to keep  the  temperature sufficiently high to  insure the 
OF MICROSCOPIC OBJECTS.
117
perfect fluidity of the  mixture.   The tin bath is,  perhaps, most
convenient when made like a small shallow cistern ;  but some
close it on the top to place the pots upon it, and alter  the  shape
to their own convenience.
   8. We Avill now inquire into some of the materials which are
needed in this operation ; the first of  AA'hich is  size.   This sub-
stance  is often used in the form of glue, but it must  be of the
very best and most transparent kind.  To make the liquid Avhich
is to receive the colours for the  usual mode of injecting, take of
this  glue seven  ounces,  and pour  upon it one quart of clean
Avater; alloAv this to stand a few hours,  and then  boil gently until
it is thoroughly  dissolved,  stirring  with a  wooden or glass  rod
during the process.  Take  all impurities  from  the  surface,  and
strain through flannel or other fine medium.  The weather affects
this a little as  to  its stiffness when cold, but this must be counter-
acted by adding a little more glue if found too liquid.
   9. Instead of glue, gelatine is generally used,  especially when
the work to be accomplished  is of  the  finer kind.  The  propor-
tions are very  different in this case, one ounce of  gelatine to about
fourteen ounces of water being sufficient.  This,  like glue, must
be soaked a  feAV hours  in  a small part of the  cold Avater, the
remainder being  boiled and added,  when it  must be stirred until
dissolved.  A good size may be made by  boiling  clean strips of
parchment for aAvhile, and  then straining the liquid Avhilst hot
through  flannel;  but Avhen the injections are to be transparent, it
is of the greatest importance that the size be  as colourless as
possible.   For this purpose  good gelatine  must  be employed, as
Nelson's or Cox's: some persons of experience prefer the latter.
   10.  Colours.   The size-solution above  mentioned  will  need
some colouring matter to render it visible Avhen  injected into the
vessels of any animal,  and different colours are used Avhen two or
more kinds of vessels are  so treated, in order  that each " set"
may be  easily distinguished by sight.   The proportion in  which
these colours are added to the size-solution may be given  as fol-
 oavs :— 
118
PREPARATION AND MOUNTING
  11. For—

  Red.....8 parts of size-solution
                     (by Aveight, to 1 part of vermilion.
  Yellow..  6      "      "        1    "   chrome yellow.
  White ..  5      "      "        1    "   flake-Avhite.
  Blue   ..  3      "      "        1    "   blue-smalt, fine.
  Black ..12      "      "        1    "   lamp-black.

Whichever of these colours is made use of must be levigated in a
mortar with the addition of  a very small quantity  of water until
every lump of colour or  foreign matter is reduced to the finest
state  possible, otherwise in the process of injecting it will most
likely be found that some of the small channels have been closed
and  the progress  of the liquid stopped.  When this fineness of
particles is  attained, warmth  sufficient to render  the size quite
fluid  must be used, and the  colour added gradually, stirring all
the time with a rod.  It may be here mentioned that where one
colour only is required, vermilion is, perhaps, the best; and blue
is seldom used for opaque objects, as it reflects very little more
light than black.
  12. When it is wished to fill the capillaries (the minute vessels
connecting the arteries with the veins), the "  Micrographic Dic-
tionary " recommends the colouring matter to be made by double
decomposition.  As a professed handbook  would be,  perhaps,
deemed  incomplete without  some  directions as to the mode of
getting  these colours, I Avill here make use of those given in that
work.   For red,  however, vermilion, as above stated,  may be
used ; but it must be carefully examined by reflected light to see
Avhether it  be free from all  colourless crystals or not.   It must
first be worked in  a mortar, and  then  the Avhole thrown into a
quantity of  water  and stirred about; after leaving it not longer
than a quarter of a  minute, the larger portions will settle to the
bottom, and  the liquid being poured off will contain  the finer
poAvder.  This may then be  dried  sloAvly,  or  added to  the size
Avhilst wet in the manner before advised.
  13. Yellow injection.—To prepare this, take— 
OF MICROSCOPIC OBJECTS.
119
       Acetate (sugar) of lead............  380 grains.
       Bichromate of potash.............  152    "
       Size............................     8 ounces.

 Dissolve the  lead salt in the Avarm size, then add the bichromate
 of potash finely poAvdered.
   Some  of the chromic acid  remains free, and is wasted in this
 solution, so the folloAving is given:—

       Acetate of lead....................190 grains.
       Chromate of potash (neutral)........100    "
       Size.............................   4 ounces.

 The first of these has the deepest colour, and is the most generally
 used.
   14.  White  injection.—This is a carbonate of lead :—

       Acetate of lead...................  190 grains.
       Carbonate of potash...............   83    "
       Size............................     4 ounces.

 Dissolve the  acetate  of  lead in the warm size, and filter through
 flannel;  dissolve  the  carbonate of potash in the smallest quantity
 of Avater, and  add  to the size:  143 grains of carbonate of soda
 may be substituted for the carbonate of potash.
   15. For blue injection, which is not, however, much used with
 reflected light, as before  stated, take—

       Prussian blue...................... 73 grains.
       Oxalic acid....................... 73   "
       Size..........,..................  4 ounces.

 The  oxalic acid is first finely powdered in a mortar, the Prussian
 blue and a little  water added, and the  whole then  thoroughly
mixed Avith the size.
  16. It may  here be repeated, that it is only  when the capillaries
are to be filled that there is any need to be at the trouble to pre-
pare the  colours by this double composition ; and, indeed, colours
ground  so finely may be procured that the above instructions 
120
PREPARATION AND MOUNTING
Avould have been  omitted, had  it not been supposed that some
students might find a double pleasure in performing as  much of
the Avork as possible by their OAvn unaided labours.
  17. The process of injection may noAV be considered;  but it is
impossible for written  instructions to  supply the place  of expe-
rience.  I will do  my best, however,  to set the novice at least in
the right way.   There are two kinds of injection—one Avhere  the
object and  colours are  opaque, and consequently fit for examina-
tion by reflected light  only;  the other, Avhere the vessels  are
filled Avith transparent colours, and must be vieAved by transmitted
light.  The first of these is most frequently employed, so Ave will
begin with it.  In  the  object which  is to be injected a  vessel of
the  kind which Ave wdsh to be filled must  be found ; an opening
must then be  made in  it to allow one of the small pipes before
mentioned to be  thrust some distance within it.   When this is
accomplished, thread  the  curved needle  with a  piece of silk
thread, or very fine  string, which  some operators  rub well with
beesAvax.   This thread must not be too thin, else there is danger
of cutting the vessel. The cord is then  carried under the inserted
pipe, and the vessel bound tightly upon  it, the ends being brought
up  round the  transverse arms, and there tied ; so that all danger
of accidentally Avithdrawing the pipe is  obviated. Care must now
be used in closing  all the vessels which communicate with that
where the  pipe is  placed lest the injecting fluid escape ;  and this
must be done by tieing them with silk.   Should, however, any of
these be left open  by accident, the bullnose forceps must  be made
use of, as before recommended.
   18. The  part to  be  injected must now be immersed in warm
Avater, not, however, above 100° Fahrenheit, and be left  until the
whole is  thoroughly warmed.  Whilst this  is being done, the
coloured size must be made ready by the pot being placed in the
tin bath  of Avarm Avater, which must be of sufficient temperature
(about 110° degrees Fahrenheit) to keep it perfectly liquid.   For
the same purpose, the syringe  is often tightly covered  with  two
or three folds of flannel; and, indeed, there is no part of the pro-
cess  Avhich requires  more attention.   If the substance  to be in-
jected is too hot, it is  injured ;  whilst, if any of the  articles are
too cold, the gelatine, or size, loses a  part of its fluidity,  and con- 
OF MICROSCOPIC OBJECTS.
121
sequently cannot enter the minute  parts.  When all is prepared,
the syringe, Avith the stopcock attached, should  be Avarmed, and
then filled and emptied with  the  injecting fluid two  or three
times, care being  taken that the end of  the syringe be kept be-
neath any bubbles which  form upon the surface.   The syringe
may then be filled, and' closely  attached to the  pipe Avhich is tied
in the vessel.   With a firm and steady pressure the piston must
be  forced  doAvnAvards, Avhen the substance will be perceived to
swell, and  the colour sIioav itself in places Avhere the covering is
thin.   When the  syringe  is almost emptied of  its contents,  the
stopcock  must be turned  to prevent any escape of the injection
from the subject.  It must then be refilled, as in the first instance,
and the process repeated.   I  say  almost emptied, because it is
Avell not to force  the piston of the syringe quite to the bottom,
lest the small quantity of air Avhich frequently remains be driven
into some of the vessels, and the object be injured or quite ruined.
As the injection is proceeded Avith, it will be found that the force
required grows greater, yet care must  be taken not to use too
much,  or  the vessels  will burst,  and render all  the  labour
fruitless.   The  movement  of  the piston  must  be occasionally
so  slow  as  to be  almost  imperceptible, and for this  reason
it  is sometimes marked Avith  lines about one-eighth  of an inch
apart.
   19.  Of course, during the Avhole  process the  injecting fluid and
subject must be kept at a temperature  high enough to alloAv the
liquid  to flow freely; and  the escape of a little of it need cause
no fears to the student, as it is almost  impossible to fill any sub-
ject Avithout some  loss.  When the injected object has received
sufficient fluid, it should have a plump  appearance, OAving to all
the vessels being Avell filled.  The vessel must then be tied up
Avhere the pipe Avas  inserted, and the Avhole left in cold Avater two
or three hours, after Avhich time it may be mounted; but it may
be  ay ell to notice a feAV things  AA'hich the beginner ought to knoAv
before entering into that part of  the  process; and he may  be
here  informed that  it  is not necessary to mount the objects im-
mediately, othenvise it Avould  be impossible  for one  person  to
make  use of half of any  large subject,  as it Avould be in a state
of  decay long before each  part could  have been examined and 
122
PREPARATION AND MOUNTING
separated.   Large pieces should be therefore immersed in equal
parts of spirits of Avine and Avater, or glycerine, Avhich some think
better  still, and thus preserved in bottles until time can be given
to a closer examination.
   20.  In  operating  upon large subjects, entire animals, &c, the
constant pressure required by the piston of the syringe grows
wearisome, besides occupying both hands, Avhich is sometimes in-
convenient Avhen Avorking  Avithout assistance.  To obviate this,
another Avay of driving the  syringe Avas published in the " Micro-
graphic Dictionary" Avhich I  will quote here:—"We have there-
fore contrived a very simple  piece of apparatus, Avhich any  one
can prepare for himself, and Avhich effects the object by mechani-
cal means.  It consists of a rectangular piece of board, tAvo feet
long and  ten  inches wide, to one end of which is fastened  an in-
clined  piece of wood  (equal in Avidth to the long board, and one
foot high).  The inclined portion is pierced with three  holes, one
above  the other, into either of which the syringe may be placed—
the uppermost being used  for the larger, the lowermost for the
smaller syringe;  and these holes are of such size as freely to ad-
mit  the syringe  covered Avith flannel,  but not to alloAv the rings
to pass through them.  The lower part of the syringe is supported
upon a semiannular piece of wood, fastened to the upper end of an
upright rod, Avhich slides in a holloAv cylinder fixed at its base to a
small rectangular pieceof wood; and by means of a horizontal Avood-
en screw, the rod may be made to support the syringe at any height
required.   The handle of the  syringe is let into a groove in a stout
Avooden rod connected  by means of tAvo  catgut  strings  Avith a
smaller rod, to the  middle of which is fastened a string playing
over a pulley,  and at the end of Avhich is a hook for supporting
Aveights, the catgut  strings passing through a longitudinal slit in
the  inclined piece  of Avood."  When in use the  syringe is filled
with injecting  fluid, and passed  through one of the three holes
which  is most suitable.  The  object being placed so that the pipe
and syringe can be best  joined, the rod and strings are set in or-
der, and a weight placed on the  hook.   The stopcock  must then
be  opened  gradually, AArhen the operator Avill be able to  judge
whether the Aveight is a proper one or not: if the piston is driven
Avith any  speed, there  is  danger of injuring  the subject,  and 
OF MICROSCOPIC OBJECTS.
123
 less Aveight may be used;  if, however, the piston does  not move,
 more must be added.
   21. Such is the  method recommended by the "Micrographic  "
 Dictionary," and perhaps  it is  as good as any mechanical  plan
 could be; but where the operator is willing to undergo the labour
 of performing all this with the hand, he has a much better chance
 of succeeding, because the  pressure can be regulated so accurately,
 and changed  so  quickly Avhen  requisite, that  no mere machine
 can compete Avith it, however Avell contrived.
   22. When the beginner  attempts to inject a subject, one of his
 difficulties is finding the vessel from which to commence.  Ano-
 ther consists in distinguishing the  arteries  from  the veins; but
 this is  partly  removed by making a longitudinal incision in the
 vessel, and Avith a blunt thick needle probing a little distance into
 the  tube.  The artery will be found thicker in the coating than
 the  vein, and  the difference is  easily  perceived by this mode of
 testing: the vein is also of a bluer colour than  the artery. I say
 above, a " longitudinal incision"  must be made:  the reason for
 this is,  the artery Avhen cut across contracts considerably, and is
 lost in  the adjoining  substance; but Avhere the opening is made
 longitudinally all clanger of this contraction is obviated.
   23. The different systems  of vessels are often injected Avith
 various colours, so that their relative positions, <fec, may be shoAvn
 most clearly.   In some specimens,  the veins are  injected Avith
 white, and the arteries Avith red;  in the kidney, the urinary tubes
 are  often filled  Avith  Avhite, and the  arteries  Avith red.  Then,
 again, the liver affords  tubes for three or four colours.   But no
 Avritten instructions on the  point can  benefit the  young student,
'and he  must be content for a Avhile to employ himself Avith single
 colours  until  he has gained the  mechanical skill and the primary
 knowledge Avhich are necessary before he can make any adA'ance.
   24. We  Avill hoav  consider  the  best  methods of  mounting
 injected objects.  They must ahvays be Avell Avashed in AA'ater after
 they have been kept in any preservative liquid, using a camel-hair
 pencil to clean the surface if necessary.   Many parts  when in-
 jected are in masses, such as the lungs, liver, <fcc, of animals, and
 consequently  sections of these  must be cut.  For this purpose
 Valentin's knife is very convenient, as the thickness can be regu- 
124
PREPARATION AND MOUNTING
lated so easily; but  Avhere the injections are opaque, there is no
need to have the  sections very thin.   Some feAV of this kind un-
dergo  comparatively  little change in  dryi.ig, so that the section
may be Avell Avashed and  floated  upon the glass slide in the place
desired, where it  Avill dry perfectly and adhere to it.  It must be
then moistened Avith turpentine  and mounted in Canada balsam
like other objects.  No great heat should be used with these pre-
parations, as it is very liable to injure  them;  and some of the
colours seem to suffer a slight contraction Avhen any great degree
of Avarmth is applied.   There are many objects, hoAvever, Avhich
must  be seen in the mass to be  understood, and, indeed, lose all
their form and beauty in drying, such as certain parts of the intes-
tines, &c.  These must be mounted in fluid, Avith the precautions
noticed at length  in Chapter IV., and  for this purpose  either
Goadby's fluid, the chloride of zinc solution, or spirit diluted Avith
ten parts of distilled water, may be employed.   It is a good thing
when practicable, to mount similar objects on two separate slides,
using  different preservative  liquids, and taking the precaution of
marking each with the kind of liquid employed.  This not only
serves as a guide to what is best for certain subjects, but if one
is injured, there will  probably be a good specimen in  the other.
   25.  It  may be here  mentioned  that many are now mounting
sections of injected  substances  Avith  the balsam and chloroform
before mentioned, instead of  using balsam alone, and consider
that the labour is much lessened thereby.
   26. A description of that mode  of injection which is  most
generally  employed  has noAV been given, but. this is not the  only
method of effecting our object.  A most  ingenious  process was
invented  by M.  Doyers, requiring no artificial Avarmth, by Avhich
many beautiful objects haA'e been prepared.  Make a solution of
bichromate of potash, 524 grains to a pint of water, and throw
 this into  the vessels to be injected; then take 1000 grains of ace-
 tate of lead dissolved in half a pint of  water, and force this into
the same vessels.   A decomposition  uoav takes place in the ves-
 sels, and the yelloAV  chromate of lead is formed.  In this decom-
 position, hoAvever, the acetate of potash also is formed, and as this
 salt has an injurious action upon the cells, Dr. Goadby recom-
 mends nitrate of lead to be used, which preserves rather than de- 
                   OF MICROSCOPIC OBJECTS.               125

stroys them.   He also advises the addition of two ounces of gela-
tine  dissolved in  eight  ounces  of Avater, to eight ounces of the
saturated  solution of each salt;  but Avith this addition the hot-
water bath Avould be required to keep the injecting fluid liquid.
  27. Many  of  these are best mounted in balsam, in the same
manner as those  made  in the  ordinary Avay; Avhilst others are
best shown Avhen preserved in liquids, for which purpose Goadby's
fluid may be employed.
  28. This mode of making injections with chromate of lead is
deemed by many the  best,  especially Avhere one  colour  only is
employed.  But it must be alloAved that  there is a little more
danger of  failure Avhere two  separate fluids are used for the same
vessels.
  29. We will  noAV consider the  best  manner of making trans-
parent injections, Avhich, for many purposes, possess an undoubted
advantage over  the opaque  ones.  But it  must be remembered
that there are certain subjects  to Avhich no  transparent injection
could be  applied, as they are too thick Avhen  in  their  natural
state, and  cutting Avould  destroy all that beauty Avhich is shown
by  the  different  parts  in their relative adaptation.   For those
objects, hoAvever, Avhich  must be cut into sections to display their
wonders, or are  naturally thin—such as some of  the finer tissues,
livers, kidneys, &c.—transparency is a great acquisition, and ena-
bles us to understand the arrangement  of  the vessels more per-
fectly.   Again,another advantage is the simplicity of the process;
no  hot water is needed Avith some preparations, either  for the
subject or the injecting fluid, Avhich runs into  the minute vessels
thoroughly and  easily, whilst the cost is small.
  30. For this  kind of  injection no colour is so commonly made
use of as  Prussian blue.  It is  not a  good one, as was before
stated, for any opaque object, as the light reflected from it appears
almost black ; yet  by transmitted  light no colour is more useful,
because its  distinctness  is  equally great by  artificial light  and
ordinary daylight.   The  method of preparing this, as given by
Dr. Beale, is as  folloAvs :—
  Glycerine..............................   1  ounce.
  AYood naphtha, or pyroacetic acid..........  1^- drachm.
  Spirits  of Avine..........................   1  ounce. 
126
PREPARATION  AND MOUNTING
    Ferrocyanide (yelloAv prussiate) of potash.... 12 grains.
    Tincture of sesquichloride of iron..........   1  drachm.
    Water "................................   4 ounces.
 Dissolve the ferrocyanide of potash in one ounce  of  the Avater;
 add the tincture of sesquichloride of iron to another ounce.  Mix
 these solutions gradually together, shaking the  bottle well Avhich
 contains them—it is best to add the iron to the potash solution.
 When thoroughly mixed, these solutions should produce a dark-
 blue mixture, perfectly free from any perceptible  masses or flocculi.
 Next mix the naphtha and spirits of wine, and add the glycerine
 and the remaining two ounces of water.   This must now be sloAvly
 mixed Avith the  blue liquid, shaking  the  whole Avell in a large
 bottle whilst the two come  together.  The tincture of sesquichlo-
 ride of iron is recommended, because it can ahvays be obtained of
 a uniform strength.
    31.  Dr.  Turnbull used a mixture  slightly different from the
 above, which is made with the sulphate of iron :—
   Purified sulphate of iron................... 10 grains.
   Ferrocyanide of potassium.................. 32  grains.
   Glycerine...............................  1 ounce.
   Pyroacetic acid...........................  1| drachm.
   Alcohol.................................  1 ounce.
   Water...................................  4 ounces.
 Dissolve the sulphate of iron in one  ounce of the water, gradually
 add the ferrocyanide of potassium dissolved in another  ounce, and
 proceed as above.
   32.  Dr. Beale  also gives  us the folloAving carmine injection to
 be employed in the same  way as the blue.*  Take—

   Carmine................................. 5 grains.
   Glycerine, Avith 8 or  10  drops of  hydrochloric
       acid.................................% ounce.

   * When, however, it is desirable to cut very thin sections of the injected
 subject, the carmine is sometimes added to  a solution of  fine gelatine—
gelatine one part to Avater eight  parts.   But the warm water and mode  of
proceeding which are used with the size solutions before described will be
necessary in this case also. 
OF MICROSCOPIC OBJECTS.
127
   Glycerine (pure)........................... 1 ounce.
   Alcohol..................................2 drachms.
   Water.................................. 6 drachms.

 Mix the carmine Avith a feAV drops of water, and Avhen Avell incor-
 porated add about five drops of liquor ammoniae.   To this dark-
 red solution about half an ounce of  the glycerine is to be added,
 and the  Avhole well shaken in a bottle.  Next, very gradually pour
 in the acid glycerine, frequently shaking the bottle during admix-
 ture.   Test  the mixture with blue  litmus-paper, and  if not of a
 very ^ecidedly acid  reaction, a feAV more drops of acid may be
 added to the  remainder of  the  glycerine and mixed as before.
 Lastly, mix  the alcohol  and Avater very  gradually,  shaking the
 bottle  thoroughly after  adding each successive  portion  till the
 Avhole is mixed.   This fluid may be kept ready prepared, and injec-
 tions made very rapidly with it.
   33.  The  method of making injections Avith these colours is the
 same as Avith the gelatine mixtures  before described, except that
 no heat is required,  and consequently most of the  trouble  re-
 moved.  The bottle of the fluid must be Avell shaken immediately
 before use; and when the object is  injected, we must  alloAv it to
 remain in  a cool place for a feAV hours before cutting it.   Thin
 sections of  the  subject  may be  cut Avith Valentin's knife, as
 before  described, and  are  very beautiful  transparent  objects.
 Some  of the finer tissues, also, are sliOAvn  much better  by this
 mode of injection  than by the opaque, and are easily mounted by
 washing in clean Avater AA'hen first separated, and  floating  upon a
 slide, Avhere they  must be allowed to dry thoroughly.   They may
 then be  immediately mounted in balsam, or kept in the dry state
 until it is convenient to finish them; but in many cases this keep-
 ing, if too much prolonged, will injure the  object.   If it is  desired
 to transfer the section to another slide, it will be necessary to wet
 it thoroughly with Avater by  the  aid of a camel-hair  pencil, and
 then gently strip it off with the forceps.   When it is  wished to
 preserve injected  subjects in "masses," it must be done  by im-
 mersion  in spirit, and  the sections may be cut  at  leisure.  Most
 of these transparent objects may be mounted in Canada balsam ;
but some recommend glycerine or glycerine jelly, as allowing the 
128
PREPARATION AND MOUNTING
use of a higher power in their examination, and preserving them
in a more natural form.
   34. A feAV subjects  may  be noticed  which are Arery beautiful
when injected, and amongst these are the eyes of many animals.
They must be injected by the artery in  the  back part, and when
the blue transparent liquid is  employed, nothing can exceed the
delicate beauty Avhich some of the  membrane  bears.  It must,
however,  be dissected Avith  care, but well repays us for the
trouble.   Water-neAvts and frogs are not difficult subjects, and in
their skin and other parts are many interesting objects.   Amongst
the commoner animals—rats, rabbits, cats,  &c.  <kc.—almost end-
less employment may be found, making use either of portions or
the Avhole animal at  once.   The intestines  of many of  these are
very beautiful.   We must  divide them with  a pair of scissors
along the tube, and cleanse them from all the matter ; the coating
may then be laid upon a slide  and  any remaining impurity re-
moved Avith a camel-hair pencil and water.   When dried  it may
be mounted in balsam, and  having been injected Avith the trans-
parent blue, its minute beauty is sliOAvn most perfectly.   In in-
jecting a sheep's foot, Avhich is a good  object,  the liquid should
be forced into it until a slight paring of  the hoof shoAvs the colour
in the fine channels there.
   35. When the lungs of small  animals are injected, the finest
fluid  must be used, as some of the capillaries are so small that it
is not an easy matter to fill them properly.   And before entering
upon these subjects,  a certain proficiency in the mode of using the
syringe, «fcc., should be obtained by practising upon simpler parts.
   36. No subjects are more difficult to  inject than fish, OAving to
the extreme softness of their tissues.   Dr. Hogg recommends the
tail of  the fish to be cut off, and the pipe to be put into the
divided vessel Avhich lies just beneath the spinal column ; by which
method beautiful  injections may be made.  The gills, however,
are the most interesting part as microscopic objects.
   37. These instructions may seem very imperfect to those who
have had much experience in  this branch ;  but  they will remem-
ber that their  own  knowledge was not gained  from any written
descriptions, but was forced upon them  by  frequent failures, some
of Avhich probably Avere very  disheartening.  As I before stated, 
OF MICROSCOPIC OBJECTS.
129
 it is very difficult (if not impossible) to accomplish much without
 some knoAvledge of anatomy.
   38.  I may here mention that the transparent  injections sent
 over from  the Continent  are beautifully executed  by Hyrtl of
 Vienna (who states that the injected fluid is composed of gelatine
 and  carmine), Dr. Oschatz of Berlin, the Microscopic Institute of
 Wabern, Schaffer and Co. of Magdeburg,  and others.  Some of
 these will bear examining with a high  power.  A friend informs
 me  that he measured a vessel in a rat's tongue by Hyrtl, which
 was l-7200th of an inch in diameter, and had a clear outline with
 quarter-inch objective.  He has also made many experiments with
 the  same materials, but has as yet failed in  producing perfectly
 distinct outlines, there being a tendency of the colouring matter
 (magenta, carmine,  &c.) to diffuse itself through the coats of the
 vessels into the surrounding tissues, although  he  has  varied the
 pressure from one half a pound to sixty pounds.  He believes the
 vessels are  first Avashed out (injected with warm water and pres-
 sure applied), then some fluid introduced which renders the arteries
 impervious  to the coloured fluid aftenvards injected.
   39. He finds that after washing out the vessels as above,  the
 injecting  fluid is much more easily introduced.  He has used a
 strong  solution of 'gallic  acid previously to injecting  with  the
 colouring matter (in  one  experiment only),  and the result was
 satisfactory.   He puts the  query,—Might not carbolic acid have a
 similar effect ?  He has often used it Avith injections to preserve
 the specimens, but not in sufficient quantity to act in the way indi-
 cated above.
   Since Avriting the above, Mr. J. G. Dale, F.C.S., and I have made
 numerous experiments with carmine injection, and have at length
 been  favoured with what Ave deem success.  Some of the vessels
 in a kitten lately injected do not  exceed l-2000th of an inch in
 diameter,  and  present a clear outline Avith  one-fifth  objective.
 There is no  extravasation, neither does the colouring matter show
 any grain except when a very high power is employed.   The fol-
loAving is our process :—
   Take 180 grains best carmine; £ fluid ounce of ammonia, com-
mercial strength, viz., 0-92, or 15° ammonia meter;  3  or 4 ounces
distilled water.  Put these into a small  flask,  and allow them to
                              7 
130              PREPARATION AND MOUNTING

digest without heat from twenty-four to thirty-six hours, or  until
the carmine  is dissolved.  Then take a Winchester quart bottle,
and with a diamond mark the spot to  Avhich sixteen  ounces of
water extend.  The coloured solution  must be  filtered into the
bottle, and to  this pure Avater should be  added until the Avhole
is equal to sixteen ounces.
  Dissolve 600 grains potash alum in ten fluid  ounces of Avater,
and add to this, under constant boiling, a solution of carbonate of
soda until a slight permanent precipitate is produced.   Filter and
add water up to sixteen  ounces.   Boil and add the  solution to
the cold ammoniacal solution of carmine in the Winchester quart,
and  shake vigorously  for a few minutes.  A drop of this placed
upon Avhite filtering-paper should show no coloured ring.   If much
colour is in solution the whole must be rejected, because, although
it is  possible to precipitate all the colouring matter by the  addi-
tion  of ammonia or alum, it is not well to do so, as the physical
condition of  the precipitate is thereby altered.
  Supposing the precipitation to be complete, or very nearly so,
shake vigorously for at least half an hour, and allow it to  stand
until  quite cold.   The shaking must then be renewed for  some
time, and the bottle filled up Avith pure water.
  After alloAving the precipitate to settle a day, draw off the clear
supernatant  fluid Avith a syphon.   Repeat the Avashing until the
clear  liquid gives little  or no  precipitate Avith chloride of barium.
So much  water must  be left Avith the colour at last that it shall
measure forty fluid ounces.
  For the injecting fluid take tAventy-four ounces of the above
coloured liquid, and three ounces of good gelatine.  AUoav these to
remain together twelve hours, and then dissolve by the heat of a
water bath;  after which it should  be strained through fine muslin.
  As this injecting fluid  contains gelatine, the hot water, and
other contrivances mentioned in  a former  part of the chapter,
will  be necessary  here also, but no peculiar treatment will be
required. 
OF MICROSCOPIC OBJECTS.
131
                    CHAPTER   VII.

                       MISCELLANEOUS.

It must be evident to all readers that there are various objects of
interest to  the microscopist  Avhich cannot  be properly placed
amongst any of the forementioned classes, but must not be omitted
in such a guide as this professes to be.  Of  these may be men-
tioned the circulation of the blood in A'arious animals, the rotary
motion of the fluid in many  plants,  the best means of taking
minute photographs, &c. &c.
   Perhaps the most interesting of these objects is the circulation
of the  blood through the finer vessels of various parts of the  ani-
mals made  use of for these purposes, Avhich parts, it is  evident,
must be  very  transparent  to afford a perfect view of this pheno-
menon.  The  Aveb of the frog's foot is very frequently made  use
of, but requires a certain arrangement, Avhich Ave will now describe.
A piece of thin Avood (Dr. Carpenter recommends cork) is taken,
about eight inches long and three  Avide ; about an inch from  one
end is cut a hole,  half or three-quarters of an  inch in diameter.
The body of the frog is then  placed in a wet bag, or wrapped in
Avct calico, Avhilst  the hind-foot projects; the Avhole is then  laid
upon the  piece of Avood so that the  foot, Avhich is  left free, may
be extended  over the hole.  The web must then be spread  out,
and secured either by threads to small pins on the wood, or the
pins must be driven  through the Aveb into the Avood, and so kept
in position.  A feAV bands of tape must be passed round the body,
the leg, and the wood, to prevent any disarrangement arising from
the animal starting, &c.  Care must be taken that the tape is not
too tight,  else  the  circulation will  be very slow  or  altogether
stopped.  The wood must hoav be fixed upon the stage, with the
aperture under the object-glass : this is sometimes done by simply
binding it, or  a spring is fixed so  as to accomplish the same  ob- 
132
PREPARATION AND  MOUNTING
 ject without so much trouble.   With a half-inch power the blood
 may noAV be seen to flow very distinctly.  The frog may be used
 for hours if care is taken to prevent the web from becoming dry,
 by wetting it with a little water from time to time.  The piece
 of Avood or cork upon Avhich the frog is laid is often made to give
 place to the " frog-plates," supplied by opticians.  These are made
 of brass,  somewhat resembling the piece of wood above recom-
 mended, but each maker's  pattern  differs according to his own
 taste.
   The tongue of the frog is also sometimes used for the  purpose
 of showing the circulation of the blood, which  is done in the  fol-
 loAving manner :—The body is wrapped Avith the calico, and made
 fast to the plate as before, only the mouth of the frog  is brought
 to the opening.   The tongue  is then gently  drawn  out of the
 mouth and pinned down over the aperture, when the  circulation
 will be Avell shown. ' But, as Dr. Carpenter observes, the cruelty
 of this mode of treatment is so repulsive that it is unjustifiable.
   Tadpoles of  the frog (Avhich, of  course, are only obtainable  in
 their season) are good subjects for showing the circulation of the
 blood.  They1 are  best suited for the microscope when  about one
 inch long.  The tadpoles of the newt and toad  also are equally
 suitable.   They may be placed in a very shalloAV  glass trough
 Avith  a little Avater, and a narroAV  band of  linen bound lightly
 round in some part not required for examination, to keep  them
 from moving; or they may be laid upon a glass plate Avith a drop
 or tAvo of water, and a thin glass covering lightly bound  upon it.
 Dr. Carpenter, hoAvever, places them first in cold water, gradually
 adding Avarm until the whole becomes about 100°, Avhen the tad-
 pole becomes rigid, Avhilst the circulation is  still maintained.  I
 have not,  however,  found this  necessary, the thin glass accom-
 plishing all that is desired.  The tail is generally the most trans-
 parent, and shoAvs  the circulation best; but in some of the  newt
 larvae the  blood may be  traced  doAvn to the very extremities if
 they are not too old.  Mr. Whitney_places the tadpole upon  its
 back, by AA'hich means the heart and other  internal  arrangements
 may be seen.
   Amongst fishes also may be  found subjects for the  same pur-
pose, but they seldom furnish as good examples as those before 
OF MICROSCOPIC OBJECTS.
133
mentioned, because the blood-vessels are not nearly so abundant
as in the foot of the frog, &c.  The stickleback is, however, pro-
curable almost in any place during the summer months, and may
be laid in a shallow  trough, loosely  bound as the tadpole.  The
tail may be  covered with a piece of thin  glass to prevent him
curling it to the object-glass.  The power needed with this will
be about the same as with the other subjects—viz., half to quarter
inch object-glass.
   It is not absolutely necessary to go to reptiles or fishes for this
curious sight, as some  other animals serve [very Avell.  In  the
wings  of the common bat may be found a good subject.   These
must be stretched out  on something resembling the frog-plate
before described, when those parts near to the bones  will show
the largest vessels very clearly.   The ear of a young mouse is  an
illustration of the same phenomenon, but it is very difficult to fix it
in a good position, as these animals are so very timid and restless.
   Amongst insects also the same law may be observed, by placing
them in the " cage," or " live-box," so  as to keep them still, but
not to injure them by too much  pressure.   In certain  larvae this
is particularly Avell shown, as that of the day-fly and plumed gnat;
but in some of these the blood is almost colourless.  In the Avings
also  of many insects this circulation is well seen, as in those of the
common house-fly;  but as these  parts  become dry in a few days,
the subject should not be more than  twenty-four hours old.
   SomeAvhat approximating to the forementioned phenomenon, is
the " rotation"  of fluid  in the  cells, or, as it is usually  termed,
the circulation of the sap, of plants.  This is shown in  certain
vegetable groAvths  as  a constant stream of thick fluid, wherein
small globules are seen ;  which stream Aoavs round the individual
cells, or up the leaf,  turning at the extremity, and doAvn again by
a different but parallel channel.   There is little or no difficulty in
showing this in many plants ; but some are, of course, better than
others, and  require a  different  treatment;  we will, therefore,
notice a feAV of these.   Perhaps the best of all is the Vatlisneria
spiralis, which is an aquatic plant,  frequently grown  in, but not
really  belonging to, this  country.  As it  someAvhat resembles
grass,  the leaf is not used in its  natural state, but a thin  section
cut lengtliAvise with  a razor or other sharp instrument—this sec-
                              7* 
134
PREPARATION AND MOUNTING
tion, however, is much better Avhen the outer surface has been
first removed.  It  should then be laid upon a slide Avith a drop
or two of Avater, and  covered Avith  a piece of thin glass.  Often
the cutting of the  section seems  to  be such a shock to the leaf
that no motion is  visible  for  aAvhile, but  in  a  short time the
warmth of  an ordinary sitting-room  Avill revive  it, and Avith a
quarter-inch object-glass the currents will be rendered beautifully
distinct.  Where the " stream " is unusually obstinate the Avarmth
may be slightly increased, but too great heat destroys the move-
ment altogether.  In the summer, any of the leaves show this
" circulation" very well; but in the Avinter, the  slightly  yellow
ones are said to be the best.
   The Vallisneria requires to be cut in sections to show this.
" circulation;"  but there are many plants of Avhich it  is but
necessary to take a fragment and lay it upon a slide.  The Ana-
charis  alsinastrum is one of these:  it grows in water, having
three leaves round the stem, then a bare portion, again another
three leaves, and  so  on.   One of these leaves must be plucked
close to the stem, and laid upon a slide Avith a  drop of water.
Thin glass should be placed upon it, and along the mid-iib of the
leaves  the  " circulation" may be seen most  beautifully Avhen a
good specimen has been  chosen; but it requires  rather more
power  than the Vallisneria.   This plant is very common  in many
parts of the country,  a great  number of our ponds and streams
being literally choked up by it.   In  the  Chara vulgaris and two
or three of the Nitellae, &c, this phenomenon  may also be seen
with no preparation except plucking a part from the stem and
laying it upon a slide as with the Anacharis.   In  using the Frog-
bit, the outer part  of the young leaf-buds must be taken to obtain
the best specimens for this purpose; but a section of the stem
will also shoAv the  " circulation,"  though not so Avell.   The plants
before  mentioned are all aquatic,  but the  same movement of the
globules has been observed in several kinds of land plants, as in the
hairs upon the leaf-stalks of the common groundsel; but these do
not show it so well, nor are  they so easily managed as the above.
   Many microscopists who are not fortunate enough to be in the
neighbourhood of these plants (indeed the Vallisneria is  a foreign
one) grow them in jars, so a few remarks as to the treatment they 
                    OF MICROSCOPIC OBJECTS.               135

require will not be out of place.   The Vallisneria requires a tem-
perature not  lower than 55° or 00°, and  even  a higher degree
than this renders its growth quicker;  and no great change  must
take place  : the more  equable the temperature the  more healthy
will the plant be.   A  glass jar should be taken, having an inch or
tAvo of mould at the bottom, which must be pressed doAvn closely,
and the plant must be set  in this.  A\ ater must then be gently
poured in,  so  as not to  disturb the mould.  As this plant flou-
rishes best when the water is frequently  changed, Mr. Quekett
recommends that  the  jar  should  be occasionally placed under a
tap of Avater,  and a very gentle stream alloAved to fall into it for
several hours, by which means much of the confervoid growth
will be got rid of and  the plant invigorated.  The Anacharis may
be rooted in the earth like the Vallisneria, but a small detached
piece may be thrown  into the jar of Avater and there  left  until
wanted.  For monthslthe  "  circulation " will be  Avell shoAvn by it,
and it will probably groAv and increase. It is also very healthy in an
in-door aquarium.   It is recommended that the jars in which any
of the Chara are grown should be moved about as little as possible,
as the long roots are very  tender, and Avill  not bear agitation.
   An  object Avhich  is interesting to the microscopist, as Avell as
the unscientific observer, is the growth of seeds, as it is often  erro-
neously termed.   A shaving of the outside of the  seed is taken
and laid upon  the glass  slide; a thin glass cover is then placed
upon  it, and a drop of Avater applied  to the  edge of this.   The
water Avill  then gradually  flow under the glass and reach the sec-
tion of the seed, Avhen the transparent fibres will appear to spring
out and " groAv " for some minutes.   This, hoAvever, is  produced
by the unfolding of a  spiral  formation in the cells, and, therefore,
has really no  similarity to the true groAvth.  The seeds of the
Salvias, Collomias,  Senecio,  Ruellia, ttc, are  avcII suited for the
display of this curious sight. '
   To  Avatch the development of the spores of ferns, and the fer-
tilization and products, Dr. Carpenter recommends  the  folloAving
mode of proceeding :—" Let  a frond of a fern, whose fructification
is mature, be laid upon a piece  of fine paper, with its spore-bear-
ing surface doAviiAvards;  in the course of a  day or two this paper
will be found to be covered Avith a very fine broAvnish dust, which 
136
PREPARATION AND MOUNTING
consists of the discharged spores.   This must  be carefully col-
lected, and should be  spread upon the surface of a smoothed
fragment of porous sandstone ; the stone being placed in a saucer,
the bottom of which is covered with Avatei> and a glass ' tumbler'
being inverted over it, the requisite supply of moisture is insured,
and the spores will germinate luxuriantly.  Some of the prothallia
soon advance  beyond the rest;  and at  the  time when the ad-
vanced  ones have long since ceased to produce antheridia, and
bear abundance of archegonia, those AA'hich have remained behind
in their growth are beginning to be covered Avith antheridia.   If
the crop be noAV kept with little moisture for several weeks and
then suddenly Avatered, a large number of antheridia and  arche-
gonia simultaneously open,  and in  a  few hours  aftenvards the
surface of the larger prothallia will be  found almost covered with
moving antherozoids.  Such prothallia as exhibit freshly opened
archegonia are iioav to be held by one lob#between the forefinger
and thumb of the  left hand, so that the upper surface of the pro-
thallium lies upon  the thumb ; and the thinnest possible  sections
are then to be made  Avith  a narrow-bladed knife perpendicularly
to the surface of the prothallium.  Of these sections, Avhich after
much practice may  be made no more than 1-15th  of a line  of
thickness, some will  probably lay open the canals of  the archego-
nia, and within these, when examined with a poAver of 200 or 300
diameters, antherozoids may be occasionally distinguished."
   Another interesting object to the young microscopist is afforded
by the  spores of  the  equiseta (or horsetails, as they are  often
called).   These may be obtained by shaking the higher portion  of
the stems  when the  spores are  ripe.  They will then  fall like
small dust, and may be placed under the microscope.  The spores
are then seen to  consist  of a someAvhat heart-shaped mass with
bands  rather  intricately  curled around it.   As they  dry these
bands expand, and are seen to be four lines at right angles, Avith
the ends clubbed, as it may be called.   If, whilst watching  them,
the spores are breathed upon, these bands immediately return to
their former state,  and are closely curled around the spore;  but
as they gradually dry again  expand.   This experiment may be
repeated several times, and is a very interesting one.
   The above are the principal objects which could not possibly be 
OF MICROSCOPIC OBJECTS.
137
 included  in  any of the former chapters, but  would have  left a
 most interesting branch untouched had it been neglected.   There
 is another subject also  Avhich should not be passed by—viz., the
 production of minute pictures which serve as objects for microscopic
 examination.   I may here mention that as this manual is simply
 to  enable  the  young student to prepare and mount his objects,
 the photography of magnified objects has evidently no place here.
   Few slides  caused  so  much  astonishment as  these minute
 photographs Avhen first exhibited;  small spots were seen to con-
 tain large  pictures, and a page of printed matter was compressed
 into the one-hundredth part  of a square inch.  It would be im-
 possible in this place  to give the inquirer  any instruction  in the
 manipulation of photography, so it must be assumed that  he al-
 ready knoAvs this.
   We will first consider the process  performed by artificial light.
 The collodion  employed in  photographing generally shows as
 much  structure when magnified as is found in linen of moderate
 texture; but this is not  ahvays the case, as  some samples bear
 much  enlargement Avithout any  of this  appearance.  It is evident
 that a structure so coarse would make it entirely unfit  for these
 minute pictures, as all the small markings would be destroyed, or
 so interfered Avith that no great enlargement Avould be practicable.
 To obtain almost structureless collodion is not an easy matter, and
 a clever practitioner in  this  branch of photography states that he
 knoAvs  of  no method  to accomplish this Avith certainty, but he
 himself tries different  samples  until he falls upon a suitable one,
 Avhich he  then lays aside  for  this object.  A beneficial effect is
 often demed from keeping the collodion awhile, but this  is not
 always the case.  The  slides should be chosen of an equal  thick-
 ness, so that AA'hen focussed upon one no  re-adjustment may be
 necessary for the others.   The glass  should, of course, be free
 from any roughness, scratches, or other imperfections, and of first-
 rate quality and colour.
  The microscope  must  then be placed in a horizontal position,
 and the eye-piece removed, the stage having a small clip upon it
to keep the prepared plate in position.   The negative must then
be supported at a distance from  the  end of the microscope tube
from  Avhich the eye-piece Avas AvithdraAvn.   The distance will, of 
138
PREPARATION AND MOUNTING
course, vary  according to the relative sizes of the negative and
desired  picture.  With a one-inch object glass,  which is a very
convenient focus, it will have to be changed usually betwixt one
and  four  feet.   The  negative  must be lighted by an argand gas-
burner or camphene-lamp, and the rays rendered as parallel  as
possible by the use of a large lens placed betwixt the light  and the
negative.  It is not easy to arrange the apparatus so as to get the
light uniform; but a little practice will soon do away with this
difficulty.   Ordinary ground-glass is too coarsely grained to focus
upon, as the magnifying power  used to examine the minute re-
flection must be considerable.  One of the slides must therefore
be coated  with the collodion, submitted to the silver-bath, and
after washing with Avater be allowed to dry.   Upon this may be
focussed the reflected image, and its minuteness examined Avith a
powerful hand-magnifier, or another microscope placed behind in
a horizontal position.   When the utmost  sharpness of definition
is obtained, it is usually required to remove  the  plate a little dis-
tance from  the object-glass, as  object-glasses for the microscope
are slightly " over  corrected," and the  chemical rays which ac-
complish the photography are beyond the visual ones.  The exact
distance required  to  give a picture to bear  the  greatest  enlarge-
ment cannot be given by rule ; but experiments must be made at
first, and it will always be the same with the object-glass which we
have tested.
  The plate may now be prepared as in ordinary photography,
and  placed upon the stage whilst the light is shaded.  AVhen all
is ready, the shade is removed and the process allowed to go on,
usually  for thirty  or forty seconds;  but no certain rule can be
given as to the required time, on account of various collodions,
lamps, and powers being used.  It may be here mentioned, that
it is  Avell to contrive  some little frame  to receive the prepared
plate, as the silver bath  solution is liable to get upon the micro-
scope stage and so, to say the least, disfigure it.  When the ex-
posure has  been continued  sufficiently  long, the picture may be
developed by any of the ordinary methods, but some of the best
productions  have  been  brought out by the aid of pyrogallic and
citric acid solution, Avith the  addition of a little  alcohol.  The
" fixing " may be effected by a strong solution of hyposulphite of 
OF MICROSCOPIC OBJECTS.
139
 soda, and the picture  must then be very avcII washed with pure
 water.   When   dry,  the photograph  must  be  mounted with
 Canada balsam, in the  same manner as any ordinary  object; but
 great heat must not be used, or the picture may be injured.
   When ordinary daylight is employed for this purpose, a dark
 slide will be required for the prepared plate, in the same way as
 for photographing landscape, &c.   These dark slides are generally
 made  by each individual to  suit his particular arrangements of
 negatives, &c.; but it may be here recommended that the opera-
 tor  should  ahvays focus in the same slide  which he is about to
 use, as so small a difference in distance lies betwixt perfection and
 failure.
   For an ordinary student, perhaps the above method is that Avhich
 is the  most readily used, and  consequently the most  generally
 available; but almost every one  has a different  arrangement of
 microscope,  &c,  by Avhich he procures these minute pictures.
 Mr.  Shadbolt (one of our most successful photographers) gives the
 following instructions :—" Having removed the upper stage plate
 of a large compound microscope, I  replace it with  one of Avood,
 supplied  with  guide pins of silver wire, in order to admit of its
 supporting a slip of glass coated Avith collodion, and excited in the
 nitrate of silver bath in the usual Avay.   If the ordinary brass stage
 plate Avere left undisturbed, it  is obvious that it and the  excited
 slip  of glass Avould be mutually destructive.
   "  The microscope is now to be placed in a horizontal position,
 the  objective,  intended to produce the  picture,  made to  occupy
 the place usually filled by the  achromatic condenser on"tlie sub-
 stage of the microscope, Avhile  another  objective is screAved into
 the  lower end of  the body of the instrument, which is  used not
 only to focus with, but also to make  the requisite  allowance for
 actinic variation.
  " The negative intended to be reduced is then  arranged verti-
 cally, with its centre in the axis of the microscopic body, at a dis-
tance of from tAvo to four feet from  the lower object-glass, and
 Avith a convenient screen of card, Avood, or thick paper, to cut off
any  extraneous light that Avould othenvise pass beyond the limits
of the picture.
  " A  small camphene-lamp is employed for  the purpose of illumi- 
140  PREPARATION  AND MOUNTING  OF MICROSCOPIC  OBJECTS.

nating the negative, having a good bull's-eye lens as a condenser,
so arranged with its flat side next the lamp that the  refracted rays
shall just fill the whole of a double  convex lens of about six inches
in diameter, the latter being placed in such a position as to refract
the rays of light in a parallel direction upon  the negative.   By
this arrangement the bulVs-eye lens of about two inches and a half-
in diameter appears as the source of the light instead of the small
flame of the lamp.
   " By using a bat's-wing gas-burner of a good size, a single lens,
instead of the two, may be  so  placed  as to give the necessary
uniformity  of illumination."
   This arrangement requires the  same care in working as that
before mentioned, the picture being produced, developed, and fixed
by the same treatment.
   As before stated, almost every manipulator makes some small
changes in the method of producing  these minute  pictures;  but
the rules given, though far from new, are sufficient for all purposes;
and I may state with truth, that  those which I procured Avhen
these wonders were quite new, are fully equal in every respect to
the best usually met with at the  present time.
   With these instructions I shall close my Handbook, as I believe
that every  branch of Preparation  and Mounting of Microscopic
Objects has been treated  of.  Not that the beginner can expect
that he has nothing to do  except read  this to be able  to mount
everything  ; but there are difficulties from which he may be freed
by instruction, when otherwise he  would have been compelled to
learn by failure alone.  I may, here, however, repeat certain ad-
vice before given,—that, when  practicable,  it is a good thing to
mount each object by two or more different methods, as very fre-
quently one feature is best shown dry, another in liquid,  and a
third in balsam.  Secondly, let the mounting be studied thorough-
ly, as no part of the microscopic science is more worthy of thought
than  this.  And lastly, let no failures prevent you folloAving up
what will assuredly one day become a source of great pleasure,
and render your daily " constitutional Avalk," which is often  dull
in the extreme, very delightful, as it will afford  you some new
wonder in every hedge-rovr. 
INDEX.
 AlR-BUBBLFS, 57.
 Air-pump,  19;  use of, 58.
 Alcock, Dr., on  tongues of Mollusca,
   111.
 Alga?, mounting of, 88.
 Anacharis  aUinastrum,  rotation  in,
   134;  to cultivate, 135.
 Animal tissues, dissection of, 108.
 Antennas of insects, 70; in  preserva-
   tive liquid, 91.
 Apparatus  required in mounting  ob-
   jects,  1.
 Arteries, how to distinguish, in injec-
   tion, 123.
 Asparagus,  spiral vessels of, 108.
 Asphaltum, 21;  and  india-rubber, as
   cement and varnish, 24.

 Bat, circulation  of blood in wings of,
   133.
 Beale's, Dr., Prussian  blue  for  inject-
   ing, 125; carmine, 126.
 Bell-glasses, use of, 19.
 Berg-mehl,  43.
 Bermuda earth, 43,
 Bichromate of  lead,  injection  with,
   124.
 Bird,  Dr. Golding,   on preparation of
   Zoophytes, 65.
 Black-japan, as a cement, 22.
 Black varnish,  23.
 Blood, as a microscopic  object,  52  ;
   circulation of, 131-140.
Bone, sections of, 97 ;  fossil, 99.
Brass plate for heating glasses, &c, 19.

CactacExE,  raphides of, 54.
Camel-hair pencils, use of, 17.
 Canada balsam, 20;  with chloroform,
   20, 61, 124;  with turpentine,  21;
   air-bubbles in, 57 ;  Dr. Carpenter's
   syringe  for, 59; to fill cells with,
   ib.; mounting of objects in, 57.
 Carbonic acid, 83.
 Carmine injecting  fluid,  Dr. Beale's,
   125 ; Dale  & Davies', 129.
 Cartilage, dissection of, 108.
 Castor oil,  as  a preservative, 83.
 Cells for dry  objects, 13 ;  with ringa
   of cardboard, 15; with gutta-percha,
   14;  with leather, ib.;  with ivory,
   15 ;  with thin glass, 14 ;  with var-
   nish, 28, 31 ;  for balsam,  59;  for
   preservative  liquids, 84-87 ; Shad-
   bolt's turntable useful in making, 16.
 Cements, 20-23.
 Chalk, foraminifera from, 63.
 Chara vulgaris, rotation in, 134.
 Chloride of zinc, solution  of, 83; of
   calcium, solution of, 89.
 Chloroform, use of (nee  Canada bal-
   sam).
 Circulation of  blood, 131-133  ; of sap
   (see Rotation).
 Cleanliness in  microscopic work, 9.
 Coal, sections  of, 95.
 Collection of diatoms, 33.
 Colours for injection,  117-119.
 Condenser, cheap, to make, 26.
 Corals, sections of, 95.
 Corallines,  to mount, 50.           *
Cover of objects,  to remove, 61.
Crystals, mounting of,  dry,  52;   to
   vary form of, and mount in balsam,
   73; sections of, 104
Cuticle of equisetum, <fec, 79. 
142
INDEX.
Dale & Davies',carmine injection, 129.
Deane's gelatine,  82.
Decalcifying process for shells, 94.
Desmidiaceae, in preservative liquid, 89.
Diacliaea elegaus, 54.
Diamond beetle, 55.
Diatomaceae, nature of, 32 ; collection
   of, 33; in stomachs of fish, 34;  to
   prepare and mount dry, 34-43 ; Mr.
   Rylands on,  37; in guano, 42 ; fos-
   silized, 43 ; mounting in balsam, 61  ;
   mounting in preservative liquids, 89.
Discs used  in mounting, 27 ; support-
   er, Smith & Beck's, 28.
Dissection,  ] 05 ; microscope for, ib.;
   instruments for, 106.
Distilled water, as preservative liquid,
   81.
Doyer's, M., method of injection, 124.
Dry objects, to mount, 27.

FjcniNODERMATA  spines, sections o£
   94.
Eel, scales of, 76.
Eggs of insects, 91.
Elastic objects, to keep flat upon the
   slide, 18.
Electrical cement, 22.
Equisetaceae, 79;  spores  of, 136.
Erector, not indispensable, 25.
Eyes of insects, 69, 56; of animals in-
   jected, 128.

Feathers, 72.
Feet of insects, 55, 71.
Ferns,  52; development of spores of,
   135.
 Fish, fins  and tails of, 52; scales of,
   55,  77; injection of,  128;  circula-
   tion  of blood in, 132.
 Flint, sections of, 96.
 Fluid,  mounting objects  in, 81.
 Flustra avicnlaris, 77.
 Fly (wc Insects).
 Foot of sheep injected, 128.
 Foraminifera, 44 ; separation  of, ib.;
   to clean, ib.;  to  clean from tallow
   soundings, 45;  to  mount,  47, 63;
   from chalk,  63.
 Forceps,  ordinary and  wooden,  18;
   bull-nosed, for injection,  116.
 Fossil infusoria, 43.
 Frog, injected, 128;  to show circula-
   tion of  blood,  131.
Frog-bit, rotation in, 134.
Fruit-stones, sections of, 99.
Fungi, 54, 90.

Gastric teeth of insects, 113;  of mol-
  luscs, 111.
Gelatine for  injection, 117; preserva-
  tive liquid, 82.
Glass slides, 9 ;  thin, 10 ; thin, to cut,
  11; thin, to  measure, 12;  thin, to
  clean, ib.;  cells, to make, 85; rings
  for cells, 86 ;  tubes, 17.
Glycerine. 82, 91 ; jelly, 82, 88.
Goadby's fluid,  83.
Gold-size, 22.
Grasses, 79.
Grasshopper, gizzard of, 113.
Guano,  containing Diatomaceae, 42.
Gum-water, and modifications of,  23.
Gutta-percba cells,  14; for liquids, 85.

Hairs, vegetable, 49 ; to mount  dry,
   56; to mount as  polarizing objects,
   77 ; sections of, 100.
Hepworth, Mr., on  mounting insects,
   68.
Horn, sections of, 99.
Hot-water bath, use of, 59.

Infusoria, in preservative liquid, 89;
   fossil, 43.
Injections,  115; apparatus  for,  ib.;
   colours for, 117 ; directions for,  120;
   with various colours, 123; mount-
   ing of, ib.; transparent, 125, 129.
 Insects, scales of, 50 ;  to  mount, 51;
   legs  and feet of, 55, 71: eyes of, 56,
   69;  Mr.  Hepworth on mounting,
   68;  antennae, of,  70;  mouth of, 71;
   tracheae and  spiracles of,  72,  109;
   parasitic, 72; in preservative liquid,
   91;  eggs of,  ib.; gizzard  of,  113;
   circulation of blood in, 133.
 Intestines, injected, 128.

 Knives  for  dissecting,  106; Valen-
   tin's, 102.

 Labelling of objects, 25.
 Lamps, for mounting, 19.
 Larvae, skins of, 52.
 Leaves, sections of, 102 ; scales of, 49,
   79.
 Liquid-glue, 22.
 Lungs of animals injected, 128. 
INDEX.
143
 Mallow, pollen of, 49.
 Marine glue, 21.
 Microscope  for dissection, 105.
 Miscellaneous, l.'il.
 Mites. 72.
 Molluscs, tongues of, 110.
 Mosses, 53 ;  in preservative fluids, 88.
 Mould (see Fungi).
 Mounting objects,  apparatus for,  9;
   dry, 27;  in Canada balsam, 67: in
   cells, 81.
 Mouse, ear of, 108 ; circulation of blood
   in, 133.
 Mouth of insects, 71.
 Muscle, dissection of, 108.

 Needles, how to mount, 17 ; for dis-
   section, 106;  curved, for injection
   116.
 Nervous tissue, dissection of, 109.
 Nettle leaf, 53.
 Newts, injected, 128.

 Onion, raphides of, 54.
 Orbitolite, section of, 93.
 Oxalurate of ammonia, crystals of, 74.

 Palates  of Molluscs (see Tongues).
 Papers, ornamental, to  cover slides
   15, 31.
 Photographs, microscopic, to produce,
   137 ; Mr.  Shadbolt on, 139.
 Pipes for injecting syringe, 115.
 Podura, scales of 51.
 Polariscope,  objects for, 73-80, 99.
 Pollen,  49, 73.
 Polycystinae, preparation and mount-
   ing of, 63.
 Preservative liquids, 81 ; cells suited
   for, 84, 88.
 Prussian blue for injection, 125.

 Raphides, vegetable, 54, 78.
 Rhinoceros, horn of, 99.
 Rhubarb, spiral vessels of, 107.
 Rings and cross of crystals, 104.
 Rotation of fluid in cells of plants, 133
   -135.
 Rush, section of, 102.
 Rylands, Mr. T. G., on  Diatomaceae,
   37, 90.

 Salicine, crystals of, 74.
SaAV of Avatch-spring, 93.
 Scales of fishes, 55, 76;  of leaves, 49,
   79; of insects, 50.
 Scissors,  17; for dissection, 106.
 Sea mats, 55.
 Sea-soundings, to cleanse, 45.
 Sealing wax varnish, 23.
 Sections, 92 ; of shells, 93;  of orbito-
   lite, ib.;  of spines of  Echinoderma-
   ta, 94 ; of corals, 95; of  coal, ib.;
   of flint, 96; of teeth,  ib.; of  bone,
   97; of fruit-stones,'99; of horn, ib.;
   of whalebone,  100;  of hairs, ib.;
   of Avood, ib.;   of leaves, 102;  of
   sponges,  103; of skin, ib.; of crys-
   tals, 104; of seeds, 105.
 Seeds, 50,73 ; sections of, 105; growth
   of, 135.
 Shadbolt's turntable, 16.
 Shells,  sections of, 92;  decalcifying,
   94; laminae of, ib.
 Siliceous cuticles,  79.
 Size for injection, 117.
 Skins  of larvae, 52 ; sections of, 103 ;
   sole, 55.
 Slides, glass, for mounting objects, 9;
   glass,  to  clean,  10; wood, &c, 14;
   most useful, 15 ; to cover and var-
   nish, 32.
 Spieula, from sponges, &c, 67.
 Spines of Echinus, 94.
 Spiracles of insects, 72, 110.
 Spiral vessels of vegetables, 107.
 Split bristles, use of, 17.
 Sponges, sections of, 103.
 Spores of ferns, development of,  135 ;
   equisetum,  136.
 Starch, preparation  and  mounting of,
   78.
 Sulphate  of  copper and  magnesia,
   crystals of,  75.
 Syringe  for  Canada balsam, 59; for
   dissection, lu7;  for injection, 115.

 Tadpole, to shoAv circulation of blood
   of, 132.
 Teeth, sections of, 96.
 Thin glass,  to cut, 11 ;  to measure
   thickness of, 12 ;  to clean, ib.
Thwnites' preservative liquid, 83.
 Ticks, 72.
 Tissues,  animal and vegetable   (see
   Dissection).
Tongues or palates  of Molluscs, 110. 
144

Tracheae of insects, 71, 109.
Transfer of objects,  17.
Trough for dissection, 107.
Tubes, glass, 17.
Turnbull's, Dr., Prussian blue  for
  jection, 126.
Turpentine, use of, 58.

Universal stand, to make, 25.

Valentin's knife,  102.
Vallisneria spiralis, rotation in, 134;
  to cultivate, 135.
Varnishes, 23.
Vegetable objects, to  mount  dry, 48 ;
  to mount in jelly, 88; dissection of,
  107.


Watch-glasses,  19.
Whalebone, sections of, 100.
Wood, sections of, ib.

Zoophytes,  to mount dry,  55 ; Dr.
  Golding Bird on mounting, in bal-
  sam, 65 ; as polarizing objects, 77. 
 


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