EX LIBRIS

William Healey Dall

Division of Mollusks
Sectional Library

MODE OF FORMATION

SHELLS OF ANIMALS, &c.

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APR 15 1988
LIBRARIES

MODE OF FORMATION

ON THE

OF

SHELLS OF ANIMALS, OF BONE,
fs oF
SEVERAL OTHER STRUCTURES,
ive
A PROCESS OF MOLECULAR COALESCENCE,

DEMONSTRABLE TN

}
CERTAIN ARTIFICIALLY FORMED PRODUCTS./

BY

GEORGE RAINEY, M.R.CS.,

LECTURER AND DEMONSTRATOR ON SURGICAL AND MICKOSCOPICAL ANATOMY AT
ST. THOMAS’S HOSPITAL.

Division of Moluaks

LONDON Sectionc! Library
JOHN CHURCHILL, NEW BURLINGTON STREET.
1858.

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Fed

PRINTED BY J. E. ADLARD,
BARTHOLOMEW CLOSE.

PREFACE.

A eruat variety of subjects being treated of in the
following pages, it must follow that some of the facts
and views therein mentioned have been previously
described or suggested by others; but as the facts
and views to which I allude are for the most part
of a general character, and of dubious authority, |
have thought it better to refrain from mentioning
names in connexion with them, than to attribute their
origin to wrong authors, especially as the mention of
them here will not m any way interfere with the claim
to priority of those with whom they originated. I may
observe that a portion of the matter comprised in
the following treatise has already appeared in the
‘British and Foreign Medico-Chirurgical Review ’ for

October, 1857, and a portion in the ‘ Quarterly Journal

vl PREFACE.

of Microscopical Science,’ for January, 1858 ; but that
many fresh facts, both physical and anatomical, are
here introduced for the first time. What im this
treatise I consider to have entirely originated with
myself, are—Firstly, a process by which carbonate of
lime can be made to assume a globular form, and the
explanation of the nature of the process, ‘“ molecu-
lar coalescence,” by which that form is produced. _
Secondly, the explanation of the probable cause of
crystallization, and the manner in which the rectilmear
form of crystals is effected. Thirdly, the discovery
of a process of “molecular disintegration” of the
globules of carbonate of lime by inverting the me-
chanical conditions upon which their previous globular
form had depended. Fourthly, the recognition, im
animal tissues, of forms of earthy matter analogous
to those produced artificially. And fifthly, the deduc-
tion from the above fact, and considerations of the
dependence of the rounded forms of organized bodies
on physical and not on vital agencies. Bemg anxious
to present the results of my experiments and observa-
tions to the public in as demonstrable a form as
possible, I have, for the convenience of those who

wish to repeat and to extend them, given in detail all

PREFACE. vu

my processes and formule ; and in the Physiological
Section of this work I have mdicated the animals and
parts best fitted for displaying the facts here described,
with the best way of preparing them for microscopical
examination. And in conclusion I may add, that I
shall be glad to show, to such as are interested in the
subject, those preparations in my possession which
have been frequently referred to in the body of this

work.

G,. BR:

9, Cuurcu Roan, Homerton;
October, 1858.

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CONTENTS.

Introductory observations

Process for making Artificial Caleuli

Mode of mounting Artificial Calculi

Explanation of the process of Coalescence

Attraction of Gravitation the cause of Coalescence
Molecular agitation

Molecular disintegration

Dumb-bell-shaped Caleuli ‘

Elliptical Caleuli becoming spherical and ieaated
Density of Calculi varies as the distance from the centre
Another cause of Lamination

Flat appearance of Calculi under the miceeohe
Calculi formed by the coalescence of several small ones
Inertia the cause of Lamination

. Coalescence of Large Calculi similarly fomenteds
Radiating lines in Calculi

Nature and cause of Crystallization

Rectilinear arrangement to the effect of a separating fore :

Tenacity or attraction of tenacity

Calculi composed of carbonate of lime and tele Pisin
Change of the crystalline into the globular form

Effect of globular carbonate on glass

Attraction of tenacity neutralized

Change from the globular to the crystalline ani by heat

x CONTENTS.

Sudden productions of Crystals by heat

Crystallization the effect of an impulsive force

The impulsive force causing app as inferred to be
Electricity .

Explanation of the manner in aseh rebels dane are
produced

Explanation of the mode a3 aeatecion of ot ee ties in
Caleuli 1

Complete molecular disiataation

Experiment showing complete molecular ieaiegiton pede
by keeping Calculi in a denser solution

Experiments showing complete molecular cameo in Gale
composed partly of vegetable matter

Experiment showing complete molecular disintegration by de-
positing paonae of lime upon Calculi perfectly performed

Time an element in the operation both of coalescence and
disintegration

The form of ultimate Molecules or Atoms

PuystoLogicaL Part.—Introductory observations

Formation of Calculi found in the Urine of the Horse

These Calculi considered as organic formations

Views of the Cell-germ theory

Mode of formation of Calculi occurring in the vine of the oiee

Vitality not connected with the formation of these Calculi .

** Animal basis”’ exists in Artificial Caleuli—Experiment showing
the fact

Structure of the Shell- detect in Crabs

Vertical section of the Crab-shell—Precautions in pernibiri stich

Craw-fish well suited for the examination of Shell-tissue

The radiating lines explained, not tubules

The structure of Crab-shell compared with Ivory

The Dentinal Canals not regular Tubules

Regular tubes in Shells not analogous with so-called Toetitarnl
Tubes

The part of Crab-shell aed Mpodernats rel esa for showing
molecular coalescence :

PAGE

76

77
78
89
83
84
86
87

8$

89

CONTENTS.

Comparison of Natural and Artificial Products

Alkaline Carbonate formed on surface of Crustaceans aera
with Shell 3 :

Chemical conditions for the formation and coalescence of

Carbonate of Lime in Crustaceaus : 2
The part which vitality takes in the formation of Organic
Structures

Formation and coalescence of G@aangte on the eden of
Crab

Chemical conditions necessary ae the formation of Carbonate of
Lime on the Apodemata

Blastema, its signification, according to both views

On the Shells of Molluses

Part of the Shell of Oyster best for Sa ee,

Lime composing the Carbonate comes directly from the rates

The Nacreous Lustre not due to the plications of Membrane

Chemical conditions for the formation of Carbonate in Oyster

The formation of Interlaminar Cavities in Oyster

The ultimate of the Carbonate of Lime in the Shells of MoHGses

Amorphous state of Carbonate in Oyster-shell

Conferve in Oyster-shell

Arguments against the view of Cells being ferred first, ai the
Carbonate deposited in them :

Formation of Carbonate of Lime on Membranes have ene

Rhombohedral masses resembling Crystals

** Prismatic Cellular Substance” in shell of Pinna

Structure and formation of Bone

Use of Carbonate of Lime in Bone

Formation of Lacune and Canaliculi

The Nucleus in Lacune

The use of Lacunie, Canaliculi, &e.

The chemical conditions under which the ear thy macs is
deposited

Sclerous vegetable tissue ;

Formation of less dense tissues by coalescence

The physical explanation applies to the formation of tissues not
to their function

Cartilage compared with artificial srodicts

Pigment-cells, development of

xl

PAGE

90
91
92
94
96

97

97

98
101
102
103
104
105
106
107
107

108
110
LUT
lll
114
116
118
121
124

127
130
131

133
135
136

xl CONTENTS.

The hooklets of the cysticercus cellulose
Crystalline lens of Fish

The way to examine the Crystalline fen
Structure of the Crystalline Lens of Stickleback
Development of Crystalline Lens :
Concluding observations on the Analogy of Nature

PAGE

137
138
139
140
144:
152

FORMATION OF SHELLS OF ANIMALS,

fe.

Tue observations about to be made upon the mode of
formation of organic structures, rest upon the fact, that,
by a proper employment of chemical and mechanical
means, and by an exact adjustment of the conditions
under which they act, calcareous bodies, identical in struc-
ture and similar in composition to the elementary forms
of the structures above mentioned, can be artificially pro-
duced. It will therefore be necessary, first, to describe
minutely the artificial process for obtaining these bodies,
and to explain the manner.in which the physical and
chemical agencies therein engaged act in producing them ;
and, secondly, to show that, wherever natural products are
found identical in structure with the artificial ones, the
existence of physical and chemical conditions, similar to
those associated in the artificial process, can be demon-
strated. :

Hence the subjects announced in the title fall naturally
under two heads: one, embracing all such considerations
as are strictly physical, and admitting of experimental
demonstration, without any possible interference from

1

2 FORMATION OF SHELLS OF ANIMALS, ETC.,

vitality, belongs to physics. The other, though connected
with structures exhibiting the same class of appearances,
and being of a similar composition, but occurring in living
parts, and therefore variously interfered with in their
development by vitality, belongs to physiology.

I shall discuss the physical part of this paper as _ briefly
as the extent and importance of the subject will permit,
and introduce into it nothing which is not either directly
or indirectly connected with physiology; but it may not
be amiss to observe, that the connexion of the two parts
is so intimate, that the latter will not be intelligible
without an adequate acquaintance with the former.

The chemical substances to be employed in the pro-
duction of the artificial calculi are, a soluble compound of
lime, and carbonate (sub-carbonate of the old pharma-
copeias) of potash or soda, dissolved in separate portions
of water; and some viscid vegetable or animal substance,
such as gum or albumen, to be mixed with each of these
solutions. And the mechanical conditions required to act
in conjunction with the chemical means, are the presence
of such a quantity of the viscid material in each solution
as will be sufficient to make the two solutions, when mixed
together, of about the same density as that of the nascent
carbonate of lime, and a state of perfect rest of the fluid
in which the decomposition is gomg on; so that the
newly-formed compound may be interfered with as little
as possible in its subsidence to the sides and bottom of
the vessel. This will require two or three weeks, or
longer, according to the size and completeness of the
calculi. But I have not found that they increase at all
after six weeks.

Now, from this process there results the simple though
very umportant fact, that when the carbonate of lime thus

BY MOLECULAR COALESCENCE. 3

formed is in a solution of a viscid material, its form, in
the place of being crystallme as when produced in the
same manner in pure or common water, is globular, and
that in this state it possesses, in a remarkable manner,
the property of coalescing with contiguous particles of the
same compound, as well as of mtimately blending with
such substances as, in its molecular state, it may happen
to be brought mto contact with; so that the minute sphe-
rules in which it first appears, if allowed to remain suffi-
ciently long within the sphere of their mutual attractions,
coalesce into large, spherical, transparent calculi, which,
if suffered to remain a sufficient time on the surface of a
glass slide, will leave permanently impressed upon it the
form of the part of the calculus which was in contact with
the glass. On reflecting upon these properties of this
form of carbonate of lime, and contrasting the conditions
under which it is formed im the experimental process, with
those which I considered would most probably be found
to be present in animal calcifying tissues—the carbonate
being in these formed and deposited in contact with a
certain amount of viscid animal matter—I expected to
find the same form of carbonate existing in the earliest
states of calcification of animal tissues, and possessed of
the same property of coalescmg and intimately blending
with contiguous structures, as that produced artificially.
Under this impression I commenced the examination of
shell-structures; but, though expecting to find some
analogy, | had no thought of meeting with so perfect a
resemblance between them, which in some instances was
so complete, that, in small portions of the two products
I was unable to distinguish one from the other, even by
the aid of polarized light. To obtain the most satisfactory
results in the investigation of the process of calcification

4 FORMATION OF SHELLS OF ANIMALS, ETC.,

of animal tissues, it is indispensably necessary that the
parts examined should be in the earliest stages of the
process, and before the calcifyimg membrane is entirely
covered with the globular coalescing deposit. The usual
plan of examining shells in thin vertical sections is entirely
useless, unless it be simply to see the number and arrange-
ment of their layers; the part of the section in such
specimens, in which the calcifying process ought to be
best seen, being entirely ground off. This part, being
the softest, can only be preserved in the process of grind-
ing by extreme care, and by keeping the lower edge of the
section always thicker than the upper.

Now, as the perfect resemblance of the globular form
of the carbonate of lime, as prepared artificially, and as
occurring in nature, indicates a corresponding similarity
in the nature of the process by which they are formed,
and an identity of the forces concerned in their formation,
the careful experimental investigation of the precise mode
of formation of the artificial products cannot fail to throw
great light upon the genesis of the natural ones, and thus
tend to emancipate this department of histology from the
obscurity in which it now hes, and bring it under the
domain of experimental physical science. Besides, I may
add that the artificial calculi, when carefully and properly
prepared, present the microscopist with a new class of
polariscope objects not exceeded in beauty or brilliancy
by any others. But even these optical phenomena, and
the physical facts connected with them, may, when more
minutely investigated, be found to possess other points of
interest besides their mere appearance ; for, occurring as
they do in bodies whose molecular constitution and mode
of formation can be demonstrated, they ought to open
new avenues to a more complete understanding of the

BY MOLECULAR COALESCENCE. 5

nature of polarized light, and to a more accurate know-
ledge of the cause of crystallization. Upon the former of
these topics I shall not be able to touch in this paper, but
I shall offer some observations upon the latter. This
globular form of carbonate of lime was first observed by
me in 1849, and was shown at that time to several of
my friends ; but I did not discover its general properties,
and its existence in organic products, until the year 1856.
I may observe, however, that in the interval between
these dates I had carefully examined a variety of morbid
products, especially a form of corpuscle called by patholo-
gists “ glomerulus,” whose globular form I felt convinced
was due to a mechanical cause; and that from this con-
viction I was led to the further examination of the bodies
I had discovered in 1849.

After numberless experiments made with a view to
determine the process best adapted for furnishing these
calculi of the largest size, and in the shortest space of
time, I found the following to answer best, which, if
strictly followed, will never fail to ensure satisfactory
results. This process is given in the ‘Transactions of the
Microscopical Society,’ published in the ‘Quarterly Journal
of Microscopical Science’ for January, 1858. It consists
in introducing into a two-ounce phial, about three mches
in height, with a mouth about one inch and a quarter in
width, half an ounce by measure of a solution of gum
arabic saturated with carbonate of potash (the sub-car-
bonate of the old pharmacopeeias). The specific gravity
of the compound solution should be 1°4068, when one
ounce will weigh 672 grams. This solution must be
perfectly clear; all the carbonate of lime which had been
formed by the decomposition of the malate of lime con-
tained in the gum, and also all the triple phosphate set

6 FORMATION OF SHELLS OF ANIMALS, ETC.,

free by the alkali, must have been allowed completely to
subside. Next, two clean microscopic slides of glass, of
the ordinary dimensions, are to be introduced, with the
upper end of one slide resting against that of the other,
and with their lower ends separated as far as the width
of the phial will permit; and lastly, the bottle is to be
filled up with a solution of gum arabic in common water,
of 1:0844 specific gravity, one ounce of which will weigh
520 grains. This solution must also be perfectly clear,
having been first strained through cloth, and then left to
stand for some days to allow of the subsidence of all the float-
ing vegetable matter. It must also be added carefully to
the alkaline solution, that the two solutions may be mixed
as little as possible in this part of the process. The bottle
must now be kept perfectly still, covered with a piece of
paper to prevent the admission of dust, for three weeks or
a month. Time would be saved by having a dozen bottles
thus charged, and examining their contents at stated
intervals, according to the chief object sought for in the
experiment. The soluble salts of lime to be decomposed
by the sub-carbonate of potash are contained in the gum,
in combination with malic acid, and also in the common
water ; ammoniaco-magnesian, or triple phosphate, is also
contained in the gum, and is set free by the alkali.
Muriate of lime, dissolved in a solution of gum from
which all the lime had been previously separated, would
answer a similar purpose, provided the muriate were not
in too great excess for the gum, in which case crystals of
carbonate would be formed together with the globules,
and the surface of the slide would become covered with
coalescing patches of the latter. Also muriate of barytes,
and muriate of strontia, when treated in the same manner
as the muriate of lime, furnish each a globular carbonate,

BY MOLECULAR COALESCENCE. "i

the spherical form of the latter being particularly perfect
and beautiful. But muriate of magnesia, when decom-
posed in the same manner, and under precisely the same
conditions, does not furnish globules, but crystals of car-
bonate of magnesia, evincing no tendency to become
globular.

After the slides have been withdrawn from the bottle,
all the globules deposited on their upper surface may be
rubbed off with the finger, or, if very closely adherent,
washed off with muriatic acid, care being taken that it
does not touch the edge of the slide, and so reach the
opposite surface. Afterwards, the lower surface, which
has the clearest and most perfect globules upon it, must
be well washed for several minutes, or half an hour, by a
stream of water running from a tap, so that all the gum
may be removed. It will then be necessary to wash it
well in distilled water, in order that no deposit from the
impure water may be left on the glass when it is dried.
The specimen, especially if it is to be put up in Canada
balsam, should now be further dried, on a plate placed
over boiling water, and afterwards washed with oil of
turpentine. In mounting these calculi in Canada balsam,
the balsam must not be boiled on the same slide as the
calculi, as, in this case, the heat employed being too
intense, would cause the calculi, containing triple phos-
phate in combination with the carbonate, to become filled
with rhomboidal crystals; but the balsam, mspissated on
another slide, may be poured hot upon the one having on
it the globules. Lastly, a thin glass cover of the width
of the slide may be placed upon it, resting at each end
upon a ledge of thin glass. The deposit which remains in
the bottle may be next examined, and put up in any way
that may be thought proper. The large ‘caleuli contained

8 FORMATION OF SHELLS OF ANIMALS, ETC.,

therein are not quite so clear as those adherent to the
lower surface of the shde, but in many respects they are
more like natural calculi.

The smaller ones are more accurately elliptical than
those on the slide, the mechanical conditions under which
they are formed being less interfered with by the attrac-
tion of the glass.

Among the facts deducible from a careful examination
of the results of these experiments, the most remarkable
and important is the perfect coalescence imto one of two
or more globules of carbonate of lime, as much as >4;5 of
an inch in diameter, perfectly transparent, of a hardness
nearly equal to that of glass, and giving the sensation,
when rubbed forcibly by the finger on a smooth, hard
surface, of small glass beads; the imeorporation of these
globules being so complete, that the resulting one has the
same spherical form, the same degree of transparency,
and the same hardness and structure as the component
ones. Let it be observed, moreover, that this is effected
without any possible assistance from the application of
external force or pressure, and that therefore it can only
be produced by the mutual attraction of the two globules.

Now, in order thoroughly to understand the cause of
this singular fact, and the manner in which the physical
forces, upon whose operation it depends, act in producing
it, every step of the process will require to be carefully
and minutely considered. For this purpose, small por-
tions of the two solutions before mentioned may be intro-
duced under a piece of thin glass fixed to a microscopic
slide, and examined by the microscope with different
magnifying powers while the solutions are blending
together and the carbonate of lime is in progress of for-
mation. The appearance which is first visible is a faint

BY MOLECULAR COALESCENCE. 9

nebulosity, at the line of union of the two solutions,
showing that the particles of carbonate of lime, when
they first come into existence, are too minute to admit
of being distinguished individually by the highest powers
of the microscope. (This examination was made with one
of Ross’s best lenses of } of an inch focus. See Fig. 1, a.)

Fig. 1.

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Tn a few hours exquisitely minute spherules, too small to
allow of accurate measurement, can be seen in the nebu-
lous part, a portion of which has disappeared, and is
replaced by these spherical particles. (See Fig. 1, 6.)
Examined at a later period, dumb-bell-like bodies will
have made their appearance, and with them elliptical par-

10 FORMATION OF SHELLS OF ANIMALS, ETC.,

ticles of different degrees of excentricity, some containing
within them one or more ellipses, more or less complete,
and parallel with the outer one. (See Fig. 1, ¢, e, and d.)
For the further examination of the globular carbonate, it
will be necessary to have recourse to those formed on
the slides, and to the deposit contained in the bottles
above mentioned. I may observe, that mixed with these
calculi, there are all those forms, with the exception of
the nebulous one, which I have just described. Fig. 2
(2 and 4) represents the forms of some of those contained

Hips 32:

in that deposit, and Fig. 3 represents calculi as they are
found on the under surface of the slides. Fig. 4 repre-
sents one form of globule sometimes found both in the
deposit and on the slides, as well as the most perfect
forms of the laminated calculi with radu. As _ these
figures, being correct delineations of the artificial pro-
ducts, will be minutely referred to when treating of the
subject of molecular coalescence, it will not be necessary
to give a written description of the forms of calculi of

BY MOLECULAR COALESCENCE. L]

which they are the accurate representations, and there-
fore I may at once proceed to consider the cause of these
several appearances, and the manner in which this cause
acts in producing them. Besides, these caleuli being
easily prepared by followmg carefully the directions
already given for their preparation, the various appear-

Fig. 3.

ances which they present in their several stages of forma-
tion can be observed by any one who likes to prepare
them on specimens of his own making.

To show that the appearances presented by the carbo-
nate of lime, as they are seen in the first experiment,
fully justify the inference which has been deduced from

12 FORMATION OF SHELLS OF ANIMALS, ETC.,

them, namely, the existence of a physical process of
coalescence of hard, solid, globular bodies, by means of
their mutual attraction, it may be observed, that the pre-
sence of these globular and oval particles, as there noticed,
can only be accounted for in one or other of two ways:
either these must have been the forms and dimensions
which they first assumed at the instant of their coming
into existence as solid bodies, or these forms and dimen-
sions must have resulted from the aggregation of pre-
existing smaller particles. Now, as im the earliest stage

Fig. 4.

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\ ‘Aw se iby) i, ie Y

of this experiment none of the larger globular and oval
particles are visible, whilst the minutest ones abound,
producing the nebulosity before mentioned—it being only
at a subsequent period, and after much of the nebulosity
has vanished, that the larger globules make their appear-
ance—it is certain, as far as ocular proof can make it,
that the larger globular and oval particles are not the first
or elementary forms of the carbonate of lime occurring in
this experiment; and hence it must follow that the second

BY MOLECULAR COALESCENCE. 13

is the only way of accounting for them—that is, that they
result from the union and intimate blending together of
pre-existing minuter particles. The same train of reason-
ing applies equally to the larger and more complex forms
of these calculi, as represented in Figs. 3 and 4, with this
additional fact, that the secondary forms, which by their
union form the largest calculi, possess characters suffi-
ciently marked to render them individually recognisable,
both when grouped together into spherical masses to
form compound calculi, and when passing through their
various changes of form, even almost up to their complete
coalescence into one perfectly spherical body. For the
satisfactory examination of these changes of form polarized
light is indispensably necessary. Now, as insuch a group
as that represented at fig. 3, c, there is no mechanical
reason deducible alone from its general figure which can
account for the fact of its contour bemg made up of arcs
of very different lengths, though of circles of nearly the
same radius, and for the arcs of the two extreme pieces
being each of them so much longer than that of the mid-
dle piece, the explanation must be sought for in some
cause which had acted upon the individual fragments ;
but as there is no conceivable combination of mechanical
forces which could have produced one part of any one of
these fragments of spheres without at the same time pro-
ducing its counterpart, these pieces must have had, when
separate, a form different to that which they have when
combined, and that form, from the figure of the different
fragments, may be inferred to have been spherical. Hence
it remains now to demonstrate in what manner the spheri-
eal figure is first given to the component globules, and,
after that, to show how these become incorporated m
those of the larger size, so as to result in the production

14 FORMATION OF SHELLS OF ANIMALS, ETC.,

of calculi of the same globular form and of the same
structure as those of which they are made up. ‘

As every particle of matter, whatever may be its form
or dimensions, is admitted by philosophers to be under
the influence of gravity, to which law, if universal, the
molecules of carbonate of lime, as produced in the manner
already described, can form no exception, it must follow
that, the instant they are brought into existence, they will
commence arranging themselves in spherical figures,
unless there should be some other force of an opposite
kind acting upon them, adequate either entirely to over-
come that of gravity, or sufficient only imperfectly to
resist 1ts influence; im which case results of an interme-
diate kind would be produced, depending upon the rela-
tive powers and modes of operation of the opposing
agencies. Now, as it is an undoubted fact, and one ad-
mitting of ocular demonstration, that the particles of carbo-
nate of lime formed by the double decomposition of a salt of
lime and carbonate of potash previously dissolved m a solu-
tion of vegetable gum, or of albumen of about the same
density as the resulting carbonate, do assume, as their first
appreciable form, that of minute spherules, and as this is
exactly the figure which the molecules composing these
particles would assume under the mechanical conditions
in which they are placed, if they were simultaneously
subjected to the effective influence of gravitation, that is,
if they attracted one another with a force varymg in-.
versely as the squares of the distances between them, and
directly as the quantity of matter in each molecule, the
sphericity of these particles may be inferred to be the
effect of gravity. And, besides, as there is no other
known agency which could produce the same results
under the same circumstances, this fact ought not only to

BY MOLECULAR COALESCENCE. ID

be looked wpon as the effect of gravity, but also as a proof
of it. There is no question but these molecules or atoms
are of inconceivable minuteness, and the spaces between
them, when they first come into existence, icomprehen-
sibly small; yet, as they are material existences, and the
distances between them real spaces, they necessarily come
within the scope of a power which is admitted to be of uni-
versal operation. If this conclusion is madmissible, then
the operation of gravity is not universal. The mode of
formation of the first set of spherical particles of carbo-
nate of lime being considered, it remains to offer a few
remarks on the manner in which these coalesce to pro-
duce the larger calculi. Now, as it has been demon-
strated by Newton, that, in a sphere the total attraction
resulting from the particular attractions of all its compo-
nent atoms is the same with respect to any body drawn
towards it, as if all the attracting particles had been con-
centrated at the centre, these minute spherical particles,
as sO many gravitating points, will be drawn towards each
other with a force varying inversely as the squares of the
distances between their respective centres; hence, being
contained in a fluid medium of an equal density, or nearly
so, in which all external sources of attraction will be
counteracted, it is evident that they will, by their mutual
attraction alone, form themselves into spherical collections
or masses. Now, as every one of the spherical particles
entering into the composition of each of these masses 1s
built up of molecules, so disposed around its centre that
every molecule is balanced and kept in its place by the
attraction of some other molecule on the opposite side of
the centre, no one of these particles can maintain its
spherical form any longer than these conditions remain
undisturbed. For it must follow that, when one of these

16 FORMATION OF SHELLS OF ANIMALS, ETC.,

spherules is brought into apposition with another of the
same kind, as must take place in the supposed conglome-
rations, the molecules of their adjacent sides will be
differently attracted from those of the remote ones, and
the balanced condition of the molecules in both will be
destroyed. Hence, the molecules which were before con-
tact at perfect rest, bemg then between equal and oppo-
site attracting forces, will now be thrown into a state of
molecular agitation, which must continue until ail the
molecules of the two spherules have arranged themselves
around only one centre, and ultimately become blended
into one perfectly spherical figure, when the mechanical
conditions necessary for molecular stasis will have become
restored. The change of form which spherical particles
undergo as they are in progress of coalescence into spheres
of larger size being attended with a certain amount of
motion of their component molecules, renders it certain
that these molecules im the individual spherules were not
in a state of absolute contact. Im this respect these
bodies are like all other hard substances; it being ad-
mitted, with the complete sanction of fact and experiment,
that the atoms of all substances, however dense, are at an
inappreciable distance apart. The fact of this motion is
shown by the simple inspection of fig. 3, e, which repre-
sents the sections of two calculi of equal size placed in
contact, also the section of one which would result from
their union, whose proper situation and relative size is m-
tended to be constructed in accordance with the fact of
the capacities of spheres being as the cubes of their radii.
The two molecules at the point of contact of these two
spheres being between equal and opposite attracting forces,
will be as if not attracted by either sphere, and therefore,
being in this way removed, each from the attractive iflu-

BY MOLECULAR COALESCENCE. 17

ence of its former sphere, they are the two molecules
which remain in contact, and will be the first to take up
a fixed position about the centre of the new sphere. Also,
the molecules composing the adjacent sides of these two
spheres, in the immediate vicinity of this central point,
being circumstanced similarly to the first two molecules,
in respect to the amount of effective force attracting them
towards the centres of their respective spheres, will be but
feebly retained in their old position, and therefore ready
to leave it, and jom those molecules which by their appo-
sition formed the central part of the sphere now in progress
of formation. For the same reason, the next and all the
circumjacent molecules contained in these hemispheres,
are less forcibly attracted towards their respective spheres,
just in proportion to their proximity to their pomt of con-
tact; and hence these molecules, bemg im a condition to
admit easily of displacement by those of the remote hemi-
spheres, whose attraction will have been less weakened,
will readily give way under the pressure of the latter,
which will be drawn towards one another en masse. The
directions taken by these molecules will be understood in
a general way by inspecting diagram e, fig. 3. All those
situated in the parts of the component spheres external to
the circular area of the resultant one will have to move
imwards towards its centre, whilst all those contained in
the parts of the component spheres nearer to the unoccu-
pied portions of area of the resultant spheres will be
carried outwards from its centre; and thus these particles
will continue to move until the area of the large circle is
filled up. Now, as the forces urging these particles in
these two directions act upon them simultaneously, each
particle in passing from its condition of rest in the com-

ponent sphere to one of rest in the resultant sphere, will
9

~

18 FORMATION OF SHELLS OF ANIMALS, ETC.,

describe a curve, whose elements might probably be de-
termined by a due consideration of the conditions of its
motion. As the principal object of this paper is physiolo-
gical, this is a task which it would be foreign to my purpose
to attempt. It will now be obvious, from what has been
stated respecting the change of position of the molecules
of two spheres in the course of their coalescence into one,
that, in a calculus made up of a conglomeration of sphe-
rules, the molecules of each spherule, having been pre-
viously arranged in reference to its own centre, will have
to leave their former positions, and pass over a certain
space before they gan gain their final positions in the
sphere of which they are to form a part. Hence, prior to
the complete coalescence of any number of spherical par-
ticles into one sphere, each particle or spherule must
undergo a process of disintegration (or be taken to pieces),
and after that, the molecules of the disintegrated spherules
must be put together again under the same static condi-
tions as they were before. These processes are not of
course performed at separate periods, so that after one is
completed the other begins; but they may both be going
on at the same time in different parts of the same
sphere. Now, the question may be raised whether
these processes are so thoroughly molecular as is here
inferred; that is, whether they extend to the actual
separation and re-arrangement of ultimate molecules
or atoms, or whether it is not sufficient that the com-
ponent spherules should be reduced only to extremely
small pieces, and these packed closely together m the
resultant spheres? As, according to this supposition, the
sclid which would result from the coalescence of these
imaginary small pieces would be a polygon, with a more
or less regular contour, and as the effect of gravity upon

BY MOLECULAR COALESCENCE. 19

particles of matter exposed to its full influence is to bring
them into the smallest possible space, that is, to arrange
them in such a solid form as presents 2 maximum of capacity
with a minimum of superficies (which is the spherical form
and that only). Gravity acting by itself, and under cir-
cumstances where it can exert its full force, cannot con-
sistently with its own laws produce such a figure as the
one above supposed, and therefore this supposition is
wholly untenable. The first effect of gravity in the for-
mation of the minutest spherules was exerted upon the
atoms or molecules of which they are formed, and no sub-
sequent operation of this force cam be complete, until
every such molecule entermg into any one calculus, of
whatever size it may be, has taken up a definite and
assigned position. It may be remarked, however, that
although this observation is strictly true, the form alluded
to is not geometrically spherical, but after all but a poly-
gon of a number of sides corresponding to that of the
molecules or atoms composing its most superficial lamina.

Having made such observations as apply generally to
the subject of the coalescence of artificially formed calculi,
and having shown that this process which, however often
repeated, affects all the molecules of these bodies, requiring
in each successive coalescence their readjustment to new
centres, must be, therefore, strictly molecular; 1 shall
now consider some particular forms of coalescmg spherules.

Fig. 2 presents accurate delineations of one or more
small globules m different stages of molecular coalescence,
from the dumb-bell figure to the perfect sphere ; (a) shows
two small spherical particles just brought into contact by
the mutual attraction of one for the other ; () two others
which have coalesced sufficiently to acquire the form of a
dumb-bell; (c) two others whose degree of coalescence is

2Ows FORMATION OF SHELLS OF ANIMALS, ETC.,

sufficiently advanced to give them the elliptical form.
Besides these there are others representing intermediate
stages. On examining specimens similar to the one of
‘which this is a drawing, a difference of structure between
the central and peripheral part in such globules (0),
especially on the side where they are in apposition, is
distinctly visible by polarized light, under which these
parts appear of different colours. And, during their
further coalescence, the central portions appear to join
before the peripheral ones; and, at a stage still more ad-
vanced, the central portions of the two spherules will be
seen to have coalesced sufficiently to circumscribe a per-
fectly elliptical area, whilst the peripheral parts, retaining
more of their spherical form, present a depression all
around their line of contact ; or, in other words, the dumb-
bell figure is retamed longer by the outer than by the
inner portions. This want of correspondence in shape of
these two parts proves that the central elliptical portion
cannot have acted as the nucleus upon which the circum-
ferential one was moulded. (See fig. 2 6 and 6.) It will
not be difficult to account for this fact on the supposition
of its being a necessary effect of attraction. Indeed, it
seems to me that the fact will do as much towards proving
the reality of the principles adduced to account for it as
any application of these principles can do towards showing
the nature and cause of the fact; or, m other words, the
fact explains itself. A few observations, however, may
make the subject more clear. For it will be evident, on the
mere inspection of the particles (0, 6’), and the illustrative
diagram a, B, C, D, fig. 2, that as the molecules occupying
the outer portions of the remote hemispheres preserve their
spherical form not perceptibly altered, they have the same
arrangement in respect to the centres of the coalescing

BY MOLECULAR COALESCENCE. 21

spherules as before contact, and therefore will exhibit
nearly the same appearance under the microscope as if
these spherules were apart. Whilst, on the contrary, the
molecules contained in the inner hemespheres, coming
within the attractive influence of both spherules, and being
simultaneously drawn in the direction of their centres by
two variable forces, whose sum is always a constant quan-
tity, will be brought under the mechanical conditions
required to give them an elliptical form, as shown in
diagram fig. 2, whose axis major is the line 4, B, and axis
minor c, D, and whose foci are the points ¢, c’, the centres
of the coalescing spherules and the coordinates of the
curve are the lines c, p, and ¢’, p. And hence the dumb-
bell-shaped particle made up of these several molecules
will refract the rays of light passing through the peripheral
portion as a sphere would, and those passing through its
central elliptical portion as an ellipse would. Hence these
rays, being transmitted differently, will render these parts
distinguishable one from the other by the microscope,
each according to its peculiar laws of transmission of
light. As the coalescence of two such spherules as those
just described progresses, the dumb-bell shape will
gradually disappear, the spherical form of the remote
hemespheres becoming changed into that of an ellipse,
so that now, the exterior outline having become also
elliptical, there results a form presenting two ellipses, one
situated within the other. (See fig. 2, c.) The still
further coalescence of these once spherical particles is
attended only with a gradual diminution of the eccentricity
of these ellipses, until, their foci coimciding, one perfectly
spherical calculus results. When, as was before observed,
the molecules will all become quiescent, being now
balanced between equal and opposite attractive forces, and

22 FORMATION OF SHELLS OF ANIMALS, ETC.,

the ultimate effect of gravity achieved. As there were,
before the figure had attained the spherical form, two
ellipses, so now there will be two spheres, one contained
within the other. (See fig. 2, c.)

The complete coalescence of two such spherules as that
last described would result in the production of one
spherule with more than two concentric zones. Hence
the careful inspection of specimens exhibiting these different
stages of coalescence brings to view numerous examples of
calculi with concentric laminz (as shown in figs. 2 and 3).
Such specimens can easily be prepared, and they occur
abundantly as organic products, showing that the existence
of rings or concentric laminze in organic bodies is not
necessarily the effect of successive depositions on its surface
as believed by physiologists and pathologists. (See
Kolliker’s ‘ Manual of Histology,’ p. 458.)

Now as these calculi are composed of only one material,
it is mexplicable on known general principles that in such
a body as the one just described, consisting of an elliptical
portion contained within an irregularly spherical one, both
without doubt in accurate apposition, the one should be so
easily distinguished by the microscope from the other.
For if this particle had been everywhere of the same
density, and if every part of it had possessed the same
index of refraction, that is, if it had been like two pieces
of any homogeneous substance, as glass, with these forms
accurately jomed by Canada balsam, one part could not
have been thus easily distinguished from the other. But
this difficulty, on the further investigation of this subject,
will be removed, when it is demonstrated that the different
parts of these globules, formed as they have been shown to
be under the influence of gravity, vary in their density
according to the degree of attraction exerted upon their

BY MOLECULAR COALESCENCE. 23

particles,—an attraction which is as their distance from
the centre. So that, this force being least at the centre,
and greatest at the surface, these differently shaped parts
will possess a density varying according to their distance
from the centre and with it also will vary their refractive
power. The effect of the diminution of refractive power
being in these calculi as the distance from the surface is
well seen on comparing them with the lenses of very small
fishes. The latter, being made densest at the centre and
least so at the surface, for the purpose of preventing
spherical aberration, present, under the microscope, when
examined by transmitted light, a spherical figure, and can
be seen to possess the property of a true lens, by one part
magnifying the other, so that the markings on the remote
surface of such a lens always appear, when seen through its
entire thickness, considerably larger than those on the
near one, and if its transparency be not much impaired,
they can be seen very distinctly. Whulst, on the contrary,
an artificially formed calculus of about the same size,
being exactly the reverse in respect to the relative density
of its different parts, causes such an amount of spherical
aberration that its form, though it may be perfectly
spherical, appears under the microscope, when viewed by
transmitted light, to be flat, and any marking on its sur-
face furthest from the microscrope cannot be seen at all
magnified by looking through it, as was observed in the
crystalline lens of the fish. This subject will be further
discussed when treating of the development of the crys-
talline lens generally. But, even so far as it has been
considered, it removes the difficulty which at first presented
itself, and furnishes incidental evidence in favour of the
principles and accuracy of the reasoning which have been
all along resorted to.

24 FORMATION OF SHELLS OF ANIMALS, ETC.,

The form of laminz just described is the effect only of
one cause of lamination; the concentric divisions thus
produced occur chiefly in the smaller spherules, where they
are generally more distinct and complete than those which
IT am about to describe. The calculi in which the nature
of the process of lamination now to be considered can
be best shown, are those which are formed by the coales-
cence of several small globules of nearly the same size.
The first stage in the formation of such calculi is a
spherical conglomeration of these globules producing a
mulberry-like appearance, (See fig. 4, 6, c, d,) and a
form closely resembling that of the corpuscle called by
pathologists a glomerulus, although that is composed of
particles of oil. The next is the disintegration of these
spherical particles which takes place first in the peripheral
ones. In this process every vestige of their original
form and structure is destroyed, and they become re-
duced to an amorphous granular mass. Next, the mole-
cules nearest to the surface coalescing, form a clear ring
completely surrounding the amorphous matter occupying
its interior. (See fig. 4, 4.) The further progress of the
processes of disintegration and subsequent coalescence is
marked by the increase in width of the circumferential
bright ring, just as the central amorphous part diminishes,
showing that the one is formed at the expense of the
other, (See fig. 4, d,) until all the latter has disappeared,
and is replaced by a succession of bright concentric
laminz. These calculi, when dried and examined by re-
flected light, have very much the appearance of small
pearls, especially the brightest of them; but after being
immersed in Canada balsam, and examined in the same
manner, they appear to consist of a glassy case, filled
with a whitish amorphous material. The relative propor- _

BY MOLECULAR COALESCENCE. 25

tions of these two parts vary according to the advance-
ment of the process of coalescence, which in very large
calculi is rarely so complete, as not to leave some remains
of the amorphous matter in the form of a central opacity,
presenting in many of these bodies the appearance of a
nucleus; in some bodies it appears to be single, but in
others to be in process of division; or, if the cause of the
appearance were not known, it might be considered as in-
dicative of fissiparous multiplication. I may observe
that this latter idea has instantly occurred to those to
whom the artificial products have been shown when
ignorant of their real nature. This latter appearance of
the nucleus will not, however, be found in calculi formed
in the manner now described, but only in those which
are formed by the coalescence of two large ones. The
central portions of each, being the last to undergo disen-
tegration and subsequent coalescence, will be recognisable
by the aid of the polariscope after all the other parts have
become thoroughly incorporated. Now, as respects the
agency of gravity (that is, the mutual attraction of the
particles of matter according to known laws), in the
formation of these calculi, it will not be doubted but that
the first stage of the formation—the collecting together
of the floating particles into spherical masses—is due to
its influence.

Next, as might have been anticipated, the peripheral
layer of these calculi is that in which the disintegration and
subsequent coalescence commence and are firstcompleted, as
indicated by the circumferential bright ring before noticed
—a fact which is in perfect accordance with the relative
force which gravity is proved to exert upon the particles
of matter arranged im spherical masses. For this force
exerting its maximum influence on the spherical particles

26 FORMATION OF SHELLS OF ANIMALS, ETC.,

composing the superficies, and diminishing in the ratio
of the distance from the centre, its effects would of ne-
cessity be apparent, first at the surface of the calculus,
and last at the centre. Hence, according to this ap-
plication of the laws of gravity, the most external layer
will be the one first formed. Now, with respect to
the subsequent layers it may be observed, that, as the
ultimate effect of gravity upon the molecules of matter is
so to arrange them that they shall occupy the least possible
space, and as the exterior molecules have been shown to
be thus arranged whilst the interior remam im their
amorphous condition, it must follow, that when the former
have undergone their final arrangement, that is, are
brought into the smallest compass, the latter will be insuffi-
cient completely to fill up the space enclosed by the outer-
most lamima, and therefore an interval will exist between
them. But the microscopic examination of such calculi
during their coalescence and lamination shows that this
process is not divided into two separate and distinct
stages, as might be inferred from this explanation (which
has only been made to present this idea to show more
clearly the facts), but that it takes place at several suc-
cessive periods, and consequently as many layers, as there
are periods of formation, are produced, one layer being
within the other. Now, as the inductive reasoning de-
monstrative of the existence of a space between the mole-
cules, when complete coalescence has been twice effected,
will apply equally if this coalescence be effected at any
number of separate times, it must follow that, as the first
jayer is larger than necessary to contain the second,
this in the same way will be too large for the third, and
so on for the rest; and hence, that there will result in-
tervals or spaces between the laminz, whatever may be

BY MOLECULAR COALESCENCE. 27

their number. Now, it may be observed, that although
this is without doubt true, the reasoning being fully borne
out by facts, still it does not necessarily follow that there
should be appreciable interlaminar spaces, but only that
there should be intervals where the molecules are less
closely aggregated than in the lamine, the difference
being only sufficient to affect the transmission of light,
both ordinary and polarized, and so to produce the ap-
pearance of laminz in the one case and that of coloured
rings in the other. This, however, is not to be considered
as the cause of lamination, but only a circumstance which
disposes to the production of laminz upon the application
of the cause. The direct cause of lamination must be
looked for in some influence which interferes with the
continuous operation of gravity. Now, imertia is exactly
such an influence, co-operating at one time with all such
obstacles as oppose the first communication of motion to
the coalescing molecules, and at another urging them to
go beyond the limits assigned by gravity. It is impossi-
ble that their motions, under such circumstances, can be
otherwise than irregular and interrupted. And the degree
of this irregularity depending also upon all other obstacles
which act upon these molecules in conjunction with in-
ertia, the number, size, and completeness of the lamin
in all those calculi must be, to a greater or less extent,
accidental. These observations are not intended so much
as an explanation of the process of lamination, as to
show that the fact of its taking place under such circum-
stances is more ‘in accordance with than opposed to
the inference that the formation of these bodies is entirely
due to the operation of gravity, and that the three stages
of their formation, namely, the collecting of the spherical
particles into globular masses, the disintegration of these

28 FORMATION OF SHELLS OF ANIMALS, ETC.,

particles, and the final arrangement of their molecules in
an obscurely laminar form, are all the effects of the opera-
tion of the same cause—universal attraction or gravity.
Before concluding the subject of lamination, the coin-
cidence and blending of the laminze of large calculi, simi-
larly laminated and of about the same size, requires
notice. (See Fig. 3, a, 6.) When such calcul as there
represented coalesce, their laminz will be seen so to coin-
cide, that, after their union is perfected, the lamine of
the resultant calculus will have the same relative position
as those of the components, so that those molecules which
were in the superficial layers of the latter will also com-
pose the same layers in the former. But, although any
given layer of the resultant sphere may contain no other
molecules than those which had existed in the correspond-
ing layers of the component spheres, yet such is the
relation between the capacity and superficial dimensions
of spheres, that all the molecules of the latter cannot be
received into the former. As, for instance, the molecules
at and near to the points of contact of the two spheres
cannot become circumferential. The mere mspection of
Fig. 3, diagram e, will show that, as in the progress of the
supposed coalescence of the two lateral spheres into the
central one, the molecules occupying the outer parts of
their surface will, from this position, be the last to reach
the line indicating the superficies of the aggregate sphere,
where they must remain; and that, as those on the parts
of their surface contained within the area of the circle
intended to represent the section of the same sphere will
be the first to be carried by the motion of the inner mole-
cules forwards to the same circle, beyond which, according
to the hypothesis, they cannot go, and consequently where
they must remain also, it must follow, that when the

BY MOLECULAR COALESCENCE, 29

coalescence is complete and all the molecules of the
lateral spheres have become collected into the central
one, its superficies will be made up entirely of molecules
which had before been contained in the superficies of the
component spheres. And as the same reasoning will apply
to the next and all the subsequent laminz, it is obvious
that the greater part of the molecules which had occupied
any given position relatively to the centre of each of the
component calculi, will be similarly placed with respect to
the centre of the aggregate calculus. If the two compo-
nent spherical caleuli be similarly laminated, as repre-
sented in Fig. 3, a and 4, it will be apparent, on inspection
of these figures, that at the contiguous extremities of
any two laminz similarly situated in the two coalescing
spheres the molecules of each lamina will be under the
same mechanical conditions; that is, the attractive forces,
acting upon the two apposed molecules in the directions
of the centres of both spheres, will, as these molecules
shift their place, be always exerted with the same intensity
upon the one as upon the other. So that when the coa-
lescence of the spheres is completed, and there is conse-
quently only one centre, these two molecules will le side
by side, equi-distant from it, both being in an arc of the
same circle. In the same manner all the other lamine
will become united, and the two spheres so completely
incorporated as to leave no vestige apparent of their
former individuality. If one of the coalescing globules
is very much smaller than the other, so that their lamine
cannot coincide, they will still become blended together,
but their molecules about the parts of junction will for
some time at least have no definite arrangement.

Besides the arrangement of the molecules of these cal-
culi mto laminz, as above described, there is also an

30 FORMATION OF SHELLS OF ANIMALS, ETC.,

arrangement of the same molecules in fine lines, of an
imperfectly crystalline structure, extending as radii from
the centre of each calculus to its circumference. These
radiating lines are not equally distinct in all calculi of the
same composition. They are, for the most part, best seen
in those of the largest size, especially when broken into
fragments, which, in consequence of these calculi splitting
up from the centre to the circumference, are wedge-shaped.
These fragments require polarized light for their exami-
nation. This singular transformation of a condition of
carbonate of lime, which, when im small pieces, was per-
fectly globular and appeared to be completely homo-
genous, into an imperfectly crystalline structure after
these same particles had become incorporated into large
spherical masses, will require now to be considered, and
the cause of the change from the globular mto the crys-
talline form explained. Now, as these changes are due
to the same arrangement of the molecules of carbonate
of lime as takes place in the production of true crystals,
they cannot be explamed intelligibly until the causes
producing the ordinary crystalline forms are fully con-
sidered ; hence the further consideration of the structure
of spherical calculi must of necessity be interrupted by
some observations upon the nature and cause of ordinary
crystallization. As crystalline forms occur in a great
many organized structures, the explanation of the causes
leading to their production must be considered as belong-
ing to the physiology of tissues, and therefore as demand-
ing the same consideration as the other constituent forms
of these tissues. Any part, to be studied properly, must
be considered in its totality, and not in reference to par-
ticular structures only. It has been observed, at the
beginning of this paper, that, when the carbonate of lime

BY MOLECULAR COALESCENCE. 31

is formed in pure or common water, its first form is crys-
talline ; but when formed in the same manner in water
containing a viscid substance in solution, its form is globu-
lar. In the former case the molecules of carbonate of lime
are uncombined, and therefore, in its crystalline state, it
may be regarded as pure; in the latter, the carbonate of
lime is combined with the viscid substance, as can be
shown by chemical analysis, and therefore in its globular
form it is obviously an impure carbonate—a compound of
this substance and gum, or albumen. The facts requiring
explanation are these: that, when the molecules of pure
carbonate of lime, that is, carbonate uncombined with a
viscid substance, come into existence, they immediately
commence arranging themselves in straight limes, and
thus, when collected together, form rectilinear figures or
erystals; but when the impure carbonate, that is, carbon-
ate combined with a viscid substance, comes into existence
under similar circumstances, its molecules assume a curvi-
linear disposition, and hence become collected mto glo-
bules. Now, as these forms of arrangement are exactly
the reverse of one another, and as the curviliear form
has been shown to be the effect of attraction, the recti-
linear arrangement might have been inferred to be the
effect of repulsion, or at least of some force causing the
separation of the elementary molecules of the pure car-
bonate. Hence it appears, that when the gum or albu-
men is intimately combined with the ultimate particles or
molecules of carbonate of lime, it confers upon them a
property capable of neutralizing this inferred repulsion ;
and thus, making the molecules of this compound indif-
ferent in respect to any inherent attraction or repulsion
existing among themselves, they become amenable to the
effective operation of gravity, a force which is ever in

32 FORMATION OF SHELLS OF ANIMALS, ETC.,

action, either effectively or imeffectively, upon the mole-
cules of all bodies. It may now be asked what the
property conferred by the viscid substance upon the car-
bonate is, and in what way it acts in producing such an
effect as that inferred. In answer I may observe, that it
is not only gum arabic and albumen which act in this
manner upon the carbonate of lime; glycerine has the
same effect, and probably all other viscid substances, if
only they are capable of combining intimately with the
nascent carbonate. Hence this effect of viscidity may
depend upon some property of animal or vegetable matter,
which is no other than a form of attraction peculiar to
organic products, differing from chemical attraction in
producing its effects, independently of any chemical change
in the substances acted upon; as, for instance, when two
recently exposed surfaces of elastic gum are brought
together, they unite without any sensible development of
chemical action, differmg from the attraction of gravi-
tation in taking place only at insensible distances, and,
lastly, differmg from that force which acts idiscrimi-
nately upon all substances, organic and inorganic, called
cohesion, in possessing in connexion with a certain amount
of adhesiveness, a degree of elasticity, the two making up
together the property called viscidity or tenacity, a pro-
perty occurring only, with the exception of certam com-
pounds of silica, in substances of animal or vegetable
origi. Now, as to its action, it may be observed that if
this power of attraction still continues to be exerted
between the ultimate molecules of this class of substances,
after their union with the carbonate of lime, as was
exerted by visible portions or large masses of these sub-
stances when uncombined, it is perfectly conceivable that
such a union would affect the repulsive or separating

BY MOLECULAR COALESCENCE. 33

force exerted between the molecules of the pure carbonate,
so as to render the molecules compounded of both sub-
stances neither attractive nor repulsive, and therefore
susceptible to the effective operation of gravity; and
certainly the fact of the ready and intimate union of these
compound molecules, as abundantly manifested im the
operation of coalescence, shows that this supposition has
a weight of evidence in its favour which amounts to proof
or demonstration that the point first supposed is in reality
a fact; and hence, considering all the circumstances of
the case, the attraction of tenacity inherent in the gum,
the repulsion or some such influence existing between the
nascent particles of the pure carbonate of lime in the act
of crystallization, and the universal operation of gravity,
it is difficult to see how the effect could have been other-
wise than experiment has shown it to be, at least in kind.
But in its amount or degree it may vary, producing all
the results intermediate between the production of im-
perfect crystals and perfect globules, according to the
relative amount of the forces in operation.

Of the three forces mentioned in the preceding explana-
tion of the manner in which the rectilinear arrangement of
the molecules of the carbonate of lime is changed into a cur-
vilinear arrangement by the action of viscid substances, the
existence of two is universally admitted by philosophers,
namely, gravity and tenacity, though the latter, if not con-
sidered a distinct force, is at least regarded as a form of
cohesive attraction ; consequently, there remains only one
force, which, having been so far only vaguely indicated as
repulsive, or capable of causing the nascent molecules of
pure carbonate of lime to assume the rectilinear or crystal-
line arrangement, demands further consideration. As the
demonstration of the nature and operation of this force, as

3

34 FORMATION OF SHELLS OF ANIMALS, ETC.,

displayed in the act of crystallization, rests partly upon
experimental and partly upon rational evidence, and as
the former will supply data for the latter, it will be neces-
sary to describe first some facts connected with the change
of the crystalline into the globular form, as well as some
facts directly connected with the production of crystals—
facts which have not been before mentioned in this paper,
but which have formed a part of a communication con-
tained in the ‘ Transactions of the Microscopical Society,’
published in the ‘Quarterly Journal of Microscopical
Science,’ for January, 1858. It has been already ob-
served that there is in gum arabic, besides malate of lime,
triple or ammoniaco-magnesian phosphate. Although
this latter compound has not to my knowledge been given
as a constituent of this substance, yet the elementary con-
stituents entering into its composition are given in the
analysis of gum by several chemists. (See Turner’s
‘Chemistry, p. 855.) When the two solutions, of the
density and composition prescribed in the formula for
making the artificial calculi, are brought together in the
manner there directed, a malate of potash and carbonate
of lime will result; and if the quantity of alkali had been
only just sufficient to neutralize the vegetable acid in
combination with the lime, the globular carbonate of lime
would have been the only compound formed and depo-
sited, while the triple phosphate would remain in solution.
But an excess of carbonate of potash is ordered to be put
into the denser solution, so that, after one portion of
alkali has precipitated the carbonate, the other may set
free the triple phosphate, and these combining form the
largest kinds of artificial calcul. Now, as the carbonate
is formed first, it will of necessity occupy a position in the
mixing fluids above that occupied by the triple phosphate,

BY MOLECULAR COALESCENCE. 35

but if the density of the two solutions be properly adjusted
(and it is upon this circumstance that the success of the
experiment mainly depends), the principal part of the
globular carbonate and triple phosphate will be produced
at about the same altitudes; and thus, their particles
beig borne up by the nearly equal density of the fluid me-
dium in which they are contained and kept in motion by
the diffusion of the unequally dense fluids, will be placed
under mechanical conditions in all respects favorable to
the mutual attraction of a great quantity of floating par-
ticles, and to their final coalescence. If the density of
the alkaline solution exceed much the degree mentioned
in the formula, and if that of the simple solution of gum
is not equal to the degree there specified, the alkali diffu-
sing itself through the simple solution of gum more
rapidly than the gum contained in the lower solution, a
larger quantity of carbonate will be formed than there
will be gum to combine with it in the proportion neces-
sary to form the globular carbonate, and, consequently,
the carbonate of lime formed in the upper part of the
bottle will be deficient in gum, and therefore it will be
erystalline and not globular. Now, as the forms of the
deposit on one of the slides employed in this experiment
will be the same as that in the fluid in contact with the
lower side of it, the position of these slides being such
that no particles in descending perpendicularly can fall
upon their lower surface, the examination of the particles
of carbonate attached to this surface will show the form
of the deposit in the corresponding regions or altitudes of
the fluid contained in the bottle, and consequently the re-
sult of the conditions stated in this experiment will be
best seen by examining the carbonate adherent to the
lower side of one of these slides. Hence, in the case just

36 FORMATION OF SHELLS OF ANIMALS, ETC.,

specified, the uppermost part of the deposit will exhibit
perfect crystals, that immediately beneath it crystals be-
ginning to have their angles rounded off, and the exami-
nation thus continued successively upon still lower por-
tions, will show the gradual passage of imperfectly recti-
linear figures into forms perfectly spherical. If, on the
contrary, the density of the lower or alkaline solution be
not sufficient, the smaller globular particles will fall to the
bottom of the bottle before they have had time to coalesce
m sufficient quantities to form the larger calculi. But
when the densities of the two solutions are properly pro-
portioned, as in the formula before given, no crystalline
carbonate will be found adherent to the upper part of the
slide, but only globular carbonate of lime; lower down
there will be the latter compound, triple phosphate, and a
mixture of the two. This mixture will be in the globular
form, and presenting different appearances according to
the relative proportions of the two component ingredients ;
if there be an excess of triple phosphate, the surface of
the calculi will be studded with minute bright crystals,
but if an excess of the carbonate no such appearance is
present, but their surface will be smooth, and their inte-
rior more or less finely lamimated. At some distance
below these nothing but crystals of triple phosphate will
be seen. Now, the examination of these crystals in refer-
ence to the gradual change their form undergoes is very
remarkable. Beginning with the lowest and proceeding
upwards, these crystals will be seen to be at first beauti-
fully perfect, presenting angles and edges sharply defined
and perfectly rectilmear. Next, as they are examined
higher on the slide, where they begin to mix with the cor-
bonate of lime, they will be observed gradually to lose
their rectilinear and angular form, and to become irregu-

BY MOLECULAR COALESCENCE. 37

larly oval, and lastly, as before observed, they become per-
fectly spherical. The transition from the crystalline into
the globular form takes place according to the increase in
the quantity of carbonate mixed with the triple phosphate,
until the quantity of the former is sufficient for perfect
globules. The incipient stage of this transition is fre-
quently indicated by a shght molecular change in the
middle of the crystals, producing a circular nebulous area,
resembling an obscure nucleus. All these appearances
can generally be seen on the slides prepared in the man-
ner before directed (at p. 5 to 7), especially if examimed
by polarized ight. As I believe no facts of a similar kind
have ever been noticed, at least in any artificial products,
though something similar is sufficiently common in natural
ones (but these have generally been attributed to a vital
cause), I will give a short explanation of what appears to
me to be the manner in which they are produced. But
first I may notice a circumstance connected with this sub-
ject which may appear singular, namely, that the triple
phosphate, produced as it 1s in the same solution of gum
as the carbonate, should not, like it, be globular, that is,
that the tenacity of the gum should not oppose the recti-
linear arrangement of the molecules of the triple phosphate,
as well as the molecules of the carbonate of ime. Proba-
bly this circumstance admits of no other explanation than
the one commonly employed in chemical reasoning, and
which may be inferred from the fact that the carbonate of
lime, having a tendency to combine with the gum, or an
affinity for it, which the triple phosphate has not, enters
into a minute state of combination with it, whilst it does
not combine in the same way, that is to say chemically,
with the triple phosphate. A similar difference has been
before observed with respect to the action of gum on the

38 FORMATION OF SHELLS OF ANIMALS, ETC.,

four alkaline earths, where it is stated that the carbonate
of magnesia is the only one which does not become globu-
lar in a solution of gum. (See p. 7.) In this respect,
there is a resemblance between the ammoniaco-magnesian
phosphate and the simple carbonate of magnesia. There
is also another fact connected with the same property of
the carbonate of lime that may be mentioned, which is its
property of combining with hard substances. This is best
shown by its action on the glass of the slide upon which
it is deposited. The particles of this substance which are
attracted by a slide and detained for some weeks in con-
tact with it, become so intimately blended with its sub-
stance that, after the surface is washed with hydrochloric
acid, impressions are left on the slide of the form of the
part of the globule attached sufficiently deep to admit of
being received on a film of collodion, on which they can
be seen by the microscope. Hence the slides which have
‘been employed in making the artificial calculi never re-
cover their transparency, but remain more or less dull
according to the time they had been in the solution of
gum. The form of these calculi becomes also affected.
The dumb-bell-shaped ones are made longer than those
which had been formed whilst floating in a fluid medium.
The elliptical particles, in the place of having a regular
elliptical contour, as when formed whilst suspended in fluid,
are lengthened, by the attraction of the glass opposing re-
sistance to the apposition of their constituent spherules.
They are also shaded off at one of their poles, that which
had been most forcibly attracted by and blended with the
surface of the slide ; and the calculi of the largest size are
flattened where they were in contact with the glass. Also,
if the surface of the slide had been scratched, the caleuli
becoming attached to these parts im greatest quantities

BY MOLECULAR COALESCENCE. 39

will be arranged in lines, the scratches generally passing
through their centres. Now, from these facts it can
easily be conceived that, when the globules of carbonate
of lime and the crystals of triple phosphate, both floating
together in the same fluid medium, are brought into con-
tact by their mutual attraction one for the other, the car-
bonate of lime will enter into intimate union or combina-
tion with the triple phosphate, as it had been before shown
to do with the glass, and form a compound of the two
substances, in which the molecules of the triple phosphate
would be brought within the sphere of the attraction of
tenacity of the gum contained in the globular carbonate of
lime. Whentherepulsive or impulsive force before operating
upon the molecules of the triple phosphate, and causing them
to be arranged in straight lines, would be neutralized by the
force of attraction of tenacity in the gum of the globular
carbonate, and the molecules compounded of the two sub-
stances being nearly indifferent in respect to any specific
attraction or repulsion now residing in their own mole-
cules, would be amenable to the effect of universal attrac-
tion, and thus undergo the same processes, first of disin-
tegration, and then of conversion into spherules, as if all
the molecules had consisted of simple globular carbonate
of lime. Decisive proofs of the existence of these pro-
cesses of disintegration and of coalescence can be seen on
examining slides containing crystals of triple phosphate
passing, as they become mixed with the particles of
globular carbonate, from the erystaline to the globular
state, already observed. Now, as in such combinations the
attraction of tenacity may be inferred to get weaker just
in proportion as the globular carbonate combines with in-
creasing quantities of triple phosphate, the attracting con-
stituent in this instance being diffused through a larger

40 FORMATION OF SHELLS OF ANIMALS, ETC.,

portion of material not possessing the property of tenacity.
Hence such relative proportions of globular carbonate and
triple phosphate may be conceived to exist together in the
same calculus as to render the attraction of tenacity acting
upon its molecules very feeble, or wholly inoperative. In
which case a compound would result, whose particles in
themselves are neither attractive nor repulsive; and
therefore, when brought together into a globular form,
would owe that form entirely to the attraction of gravita-
tion. This is an important conclusion, as such a calculus
would admit of being disintegrated, by reversing the di-
rection in which gravity, during its formation, acted upon
its molecules, provided only the attractive force im the re-
versed direction is greater than that which keeps the mole-
cules together; and thus it would be the means of adding
analytical to the synthetical evidence already advanced
on the subject of molecular coalescence. Now, I may
observe that such calculi as the above can be prepared,
and after that disintegrated, on the principle above
mentioned; but the further consideration of this subject,
with an account of the experiments required to illustrate
it, will be given in a separate article on ‘Complete or
final Molecular Disintegration.’ (See p. 54). And as this
subject throws no light on crystallization, its introduction
here would be inconvenient, and therefore I will proceed
to consider another fact, also showing the feeble condition
of the force which preserves the molecules of the caleuli
composed of the globular carbonate and triple phosphate
in their spherical form, and the near approach that there
is in these calculi to an extinction of the attraction of
tenacity. The experiment showing this fact consists in
exposing a slide prepared according to the formula, and
having upon it all the varieties of calculi already described,

BY MOLECULAR COALESCENCE. 4)

to a temperature of 212°, either by simply heating it, or
immersing it im boiling distilled water, or in oil, turpentine,
or Canada balsam raised to that heat, when the calculi
containing the triple phosphate, as well as the crystals of
the same substance, will instantly become changed into
masses of rhomboidal crystals of various sizes, whilst the
calculi composed only of globular carbonate of lime will
not be sensibly altered. Now, it must be observed, that
though the attraction of tenacity may, in the above in-
stance, have assisted in preserving the integrity of the
calculi containing the largest proportion of the tenacious
matter, yet if this attractive force exceed a certain limit,
it will prevent the act of coalescence by effectually
opposing the action of gravity in the preliminary
stage of disintegration. Hence all the phenomena of
coalescence must take place between this limit and the
total extinction of the attraction of tenacity, and it is
the result of experiment which alone can prove whether
the conditions proper for coalescence are included or not
within these two limits. The production of crystals, as
observed in this experiment, is different to that under
which crystallization ordinarily takes place. There is no
indication of a prior state of solution, or igneus fusion,
but the molecules of triple phosphate appear to pass
directly and instantaneously from one form of arrange-
ment to a different one, and, in the spherical particles,
from a curvilinear to a rectilimear arrangement. As this
takes place about the boiling point of water, it might
have been thought, especially in the case of the crystals,
to be produced by the solution of the triple phosphate in
some combined or interstitial water raised to 212°, on the
cooling of which it had again crystallized, though in a
different form. If this effect had followed only the im-

AQ FORMATION OF SHELLS OF ANIMALS, ETC.,
mersion of the slides in boiling turpentine, Canada balsam,
&c., this observation might have been true; but occur-
ring exactly in the same manner in water, it cannot be so,
as the crystals must, under such a supposition, have been
sufficiently soluble in boiling water to have been entirely
dissolved off the slide, which is contrary to the fact; hence
some other explanation must be sought for. This sudden
formation of crystals in one of these compounds, by a
cause which does not sensibly affect the other, seems to me
to admit of explanation in different ways, and on different
hypotheses. It may be supposed, that the separating force
to which the rectilinear arrangement observable in crystals
is due, is a form of repulsion, and, that in the compound of
globular carbonate and triple phosphate, the attractive and
repulsive forces acting upon their molecules are nearer the
condition of equilibrium than in the simple globular carbo-
bonate, so that when these two forces are weakened
equally in both substances by the temperature of 212°, a
preponderance of the repulsive over the attractive force,
indicated by a change of the curvilinear into the rectilinear
arrangement of the molecules, takes place in the com-
pound of globular carbonate and triple phosphate, but
does not sensibly affect the molecular condition of the
simple globular carbonate, the attraction of tenacity still
holding them together. Or, if the repulsive force were
equally augmented in both substances by the same eleva-
tion of temperature, the effect would be the same upon
the two compounds as that just mentioned. Hence the
application of heat in this experiment may have produced
the effect of sudden crystallization in two ways—either
by weakening the uniting force without affecting the
separating one, or by augmenting the separating force with-
out affecting the uniting one.

BY MOLECULAR COALESCENCE. 43

It now remains to consider to which of these forees—the
attracting or the separating one—the production of crystals
as shown in this experiment, is due. Before proceeding
further, I may observe, that the evidence, both rational
and experimental, is altogether in favour of the latter. It
was noticed in the last experiment that rhomboidal
crystals, formed in the crystals of triple phosphate, re-
sembled in every respect those formed in the globules com-
posed of triple phosphate and carbonate of lime. Hence,
in the case of these crystals, where the only force acting
upon their molecules is repulsive, as shown by the fact of
their form being crystalline, the mere change in the
arrangement of their molecules from one rectilinear figure
to another, presents nothing indicative of attraction, but
quite the contrary ; and therefore, in this instance, a re-
pulsive force must be inferred to be the sole agent con-
cerned in their production. Now, it must be particularly
noticed, that this observation applies only to the primary
act of giving to the molecules their first form, that is, to
the production of the first or primative crystals; for after-
wards these forms are joined together, and so made into
crystals of different sizes by the action of gravity. There
is a circumstance connected with this experiment requir-
ing especial notice, as calculated to throw some light
upon the nature of this and the repulsive or separating
force. The circumstance to which I refer is the sudden
and instantaneous manner in which perfect crystals are
formed, differing in this respect so much from the slow
and gradual manner in which the globules are produced.
The latter can be seen to be produced by the coalescence
of particles of all sizes, but of no exact geometrical figure,
though all curvilinear, and to increase in their dimensions
by successive coalescences or stages, one stage imper-

AA. FORMATION OF SHELLS OF ANIMALS, ETC.,

ceptibly blending with another, so that if these globules
be broken up, no definite form can be detected which can
be taken as a primary one, but everything gives indica-
tions of their formation being due to the operation of a
continuous force. The larger crystals, on the contrary,
are formed instantaneously, and built up of particles of
the same form, and doubtless of the same size, showing
that the force which was employed in their production
had been divided into separate impulses, each impulse be-
ginning and ending with one of these primary forms,
which in some degree may be taken as a measure of the
amount and an indication of the mode of operation of
the force employed; so that there is every appearance that
the formation of these crystals was the result of a succes-
sion of separate though similar impulses. Hence, the
force producing rectilinear molecular arrangement may
be inferred from this experiment to be impulsive, and thus
crystals may be considered as the result of separate im-
pulses acting upon the molecules of those substances
which assume the crystalline form. This inference is
particularly strengthened by the fact, that there exists in
nature no known force, or combination of forces, which
acting continuously and in conjunction with gravity, is
in any way adapted to produce a sustained rectilinear mo-
tion. It has been suggested that the electric and mag-
netic forces (the one always intersecting the plane of the
other’s action at right angles) are conducive to this re-
sult; but it must be remembered, that even if the pri-
mitive particles of matter were impelled in straight lines
by a rectilinear current thus produced, it would not dis-
pose them rectilinearly, unless they were solely under
its influence—a supposition which would exclude the
action of gravity, which has been shown by the facts of

BY MOLECULAR COALESCENCE. 45

molecular coalescence to act continually upon the
smallest particles of matter. Hence, if the action
of such a current were a fact, all the nascent mole-
cules of a crystallizable substance would be simul-
taneously acted upon by two very dissimilar forces,
and also in no fixed or definite direction, the direction
depending upon the position of the attracting particles m
reference to the direction of the rectilinear current, which
might at one instant oppose, at another coincide with,
at other imstants be inclined at varying angles to, the
direction of this supposed current; and thus these molecules
would either have their motion only retarded or only
accelerated, or, if neither of these effects were produced,
they would be disposed in curves depending upon the
relative intensities and directions of the motor forces, but
they would never be disposed in straight lines, as in per-
fectly rectilinear crystals. A question will now arise as to
the nature of the agency employed in the communication
of the impulsive motion to the nascent molecules of the
erystallizing substance, and its adequacy to account for all
the phenomena of crystallization. In the preceding course
of experiments crystallization is shown to take place under
two sets of conditions, differmg altogether the one set
from the other. The one is where the formation of
crystals is the result of chemical action ; the other, where
crystals are produced on the application of heat to a body
as yet not at all crystalline, or only very imperfectly so.
Now, both these are well known to belong to a class of
cases attended with an evolution of electricity ; so that, in
the first case, the molecules of carbonate of lime, the
instant they come into existence, may be inferred to be im
a state of electrical excitation, and as the composition of
every molecule is the same, and as the conditions under

46 FORMATION OF SHELLS OF ANIMALS, ETC.,

which they are all placed are alike, the electricity of every
one will doubtless be the same, and hence they will repel
one another. The second case is a mere instance of
thermo-electricity, in which electrical excitation is produced
by the unequal conduction of heat. Hence there is no
extravagancy in the inference that in both these cases the
crystallizing particles, being under the infiuence of like
electricities, should be self repulsive, or rather, as this
state is acquired in an instant, and as instantaneously
brought imto operation, self-propulsive. Indeed, the
bare fact of these particles becoming rectilinearly disposed
under such circumstances is an experimental proof of the
existence of an agency capable of exciting upon them a
repulsive power. And as there is no other known power
capable of producing, under the same circumstances, a like
effect, excepting electricity, it may fairly be considered as
the power in question. As to the adequacy of simple
electricity to account for this fact and the ordinary
phenomena of crystallization, it may be observed that the
impulsive power of large discharges of this agent are too
well known to leave any doubt upon this head. It is
certain that, in the last experiment, the sudden production
of perfectly crystalline forms in such hard globular bodies
must have required a considerable amount of mechanical
force, considering that the molecules of these bodies could
not have taken up a new position without in some degree
displacing the particles contiguous to them, and so dis-
turbing, more or less, the cohesions of the entire calculus.
But what other known force is there m nature which could
have achieved this besides electricity? Caloric, actmg m
different ways and through different means, might have
broken these bodies into pieces, but it could not have put
them together again in regular geometrical forms. To

4

BY MOLECULAR COALESCENCE. 47

demonstrate exactly in what manner the electrical force
must act upon the molecules of these calculi, as well as
upon those of other crystallizable substances in the act of
crystallization, so as to give them that crystalline arrange-
ment which they have been shown suddenly to acquire,
it will be necessary to divide, mentally, this process into
different parts, and to investigate these separately, and
afterwards to consider them as they would act together.
First, then, let the molecules about to take on the crys-
talline form be: supposed to be in isolated groups, one
group being incapable of influencing the other; and
suppose that im an instant all these molecules become
endowed with the power of repelling one another, and it
will be obvious that the molecules of each group will
suddenly become divergent and tend to arrange themselves
in a spherical form, of which the central molecule of the
group, retaining still its position, will be the centre, whilst
all those around it will be thrown into diverging lines or
radii goig from that centre. Next, suppose two such
groups of equal size, placed side by side, to be acted upon
in the same manner as the above, and it will be at once
apparent that, as their adjacent molecules are impelled in
directions which intersect one another, their motion beyond
the point of intersection would be retarded and the force
communicated to them diminished, the

y degree of diminution being as the sine

an of the angle a, c, B (see the accom-

) panying diagram). Hence, at the
point a the line a, 8 will denote the
amount of the attraction of gravita-
tion necessary to balance the force
of impulsion acting on the molecules
at a, and so to bring them into the condition of rest.

48 FORMATION OF SHELLS OF ANIMALS, ETC.,

And as the same reasoning would apply to the molecules
on the other side of the line c, c’, a quadrilateral area
would be enclosed corresponding to the superficies of a
primitive crystal. And extending this reasoning to similar
groups situated on all sides of the one first supposed, a
solid quadrilateral form would result corresponding to
that of a primitive crystal. Though all crystals thus
formed would be quadrilateral, yet their exact shape will
vary according to the size of the angle a, c, s. If this
angle be less than 45°, then, as the three angles of
every triangle are equal to two right angles, c, a, c’ will
be greater than a right angle, and the form of the crystal
represented by ac, 4c, will be rhomboidal or lozenge-
shaped. But if the angle a, c, B be exactly 45°, then the
angle c, a, B will be a right angle, and all the angles of
the figure a c, a’ c will be right angles, and therefore the
crystal represented by this figure will be rectangular.
Now the molecules at the point 3B, being impelled in
opposite directions and with an equal force, will be kept
in their place without the aid of gravity, and therefore
here, where the sine of the angle a, c, B vanishes, the
attraction acting upon the molecules will be at zero.
But as the force of attraction required to balance that of
repulsion estimated from the point B increases as the sine
of the angle a, c, B, the density of these crystals, being as
the attractive force holding their molecules together, will
be least at the centre and greatest at the surface. This
inference agrees with several recorded facts connected with
the polarization of light by crystals. As, during the
formation of the primitive crystals of different crystallizable
substances, or during the formation of those of the same
substance under different circumstances, different quan-
tities or intensities of electricity would doubtless be evolved,

BY MOLECULAR COALESCENCE. 49

whilst, under the same circumstances, and where the
chemical action had the same amount of activity, these
would always be the same, there ought to be a corre-
sponding difference in the shapes and the sizes of different
primitive crystals, agreeing with the uniformity, or want
of uniformity, of the conditions under which these crystals
ave formed. After these first crystals are thus produced,
they will become grouped together and built up by the
action of gravity into other forms depending upon the
order and manner in which they are packed together.
But, as this belongs exclusively to the subject of crystal-
lography, I shall not enter systematically into it. There
is, however, room for another observation connected
with this part of the subject. It may be asked by
what the primitive atoms or molecules are prevented from
coming into absolute contact after the cessation of the
chemical action, and the consequent evolution of fresh
portions of electricity. It is not improbable or incon-
sistent with the facts of electrical isolation, that these
molecules should be sufficiently isolated to retain their
state of electricity, and therefore continue, after the
subsidence of the chemical action, to repel one another.
However this may be, it is certain that there is one agent
of universal existence as a repelling force, namely, caloric,
which will prevent in these instances the absolute contact
of molecules. But how far caloric is rightly to be regarded
as a distinct force, or only as one of the sensible effects of
the same agency as electricity, it is not necessary here to
consider, as it is only the fact of its separating or repulsive
power which is insisted on. I may observe that the
simple rectilinear forms shown in diagram, page 47, into
which the molecules of adjacent groups are supposed to be
thrown by the impulsive forces acting according to the
4

50 FORMATION OF SHELLS OF ANIMALS, ETC.,

hypothesis, are exactly lke those of the smallest crystals
on the heated slides, before mentioned. And also it may
be observed, that in examining good specimens of these
crystals the larger can be seen to be made up of crystals
of a variety of sizes, and therefore to be divisible into
smaller ones, and these again into crystals still more
minute, though of the same form, and so on, until the size
becomes so diminutive that the true figure is inappreciable
by the highest magnifying powers. (I have slides contaiming
distinct rhomboidal crystals of 4¢'55th of an inch im length,
and containing other crystals not more than 39$5oth or
zodooth of an inch long.) Hence it may fairly be inferred
that this same form, being the simplest and most natural,
and of all rectilmear figures most easily produced, would
continue diminishing in size until a crystal would be
arrived at whose further division would separate it into its
constituent molecules, that is, into those portions of matter
which, their inertia being overcome, are the first to be put
in motion under the combined influence of impulsion and
gravity. Now, applying the reasoning employed at pages
47 and 48 to the formation of just such a crystal, it will
be seen that one of the molecules, thus impelled, which is
to form a part of this crystal, would instantly encounter
another molecule put im motion at the same time and
under the same mechanical conditions, and the two being
as instantly arrested by the predominant action of gra-
vity, would become fixed in their position. And by the
same process of reasoning, the other molecules could be
shown to be added, until the formation of the crystal
is completed, all the molecules which composed it
bemg put in motion and brought into the condition of
rest by the simultaneous operation of the same forces,
namely electricity, the agent generating the impulsive

BY MOLECULAR COALESCENCE. 51

force, active inertia, and gravity. Now, if it be admitted
that the size of this first crystal is such, that is, that its
component molecules are so close together that they are
all put in motion and afterwards brought into a state of
rest by only one impulse; or, what is the same, that the
impulse given to any one molecule could not for want of
space be repeated, then no part of a curve could possibly
enter into its contour, since this contour would on this
supposition be made up only of the first material points of
the curves which each of these molecules would describe
separately, if it continued in motion under the conjomed
effect of an impulsive and attractive force. As this
explanation perfectly agrees with the earliest appreciable
forms and appearances presented by crystallizable sub-
stances in the act of crystallizing, and as I believe it is the
only explanation which in principle can account for the
rectilinear form of crystals, produced as they are under
circumstances all tending to cause curvilinear arrangement,
it may be inferred to be the correct one. It goes also to
furnish conclusive evidence that the principle upon which
this explanation is based, and the premises from which
it has been deduced are real; and moreover it goes to
show that several of the points which have only been
assumed in the course of the discussion, or imperfectly
demonstrated, are themselves facts. Now, after a primitive
or first crystal has been thus formed, it can easily be
conceived that, as a multitude of such crystals are all
formed together at the same instant, they will be brought
by the attraction of gravitation imto apposition, and the
juxtaposition of their flat surfaces being favorable for
extensive contact, they will be forcibly drawn together,
and retained in the rectilinear form by the action of
gravity, and thus larger rectilinear crystals will result,

52 FORMATION OF SHELLS OF ANIMALS, ETC.,

which, being packed together in different ways, will
produce all the varied forms peculiar to the several classes
of crystals. Now, as the molecules or atoms composing
the primitive crystals are finite magnitudes, the same
observation will apply to the apparently smooth crystals
as was applied to the apparently spherical calculi; namely,
that as the latter were only polygons of a number of
sides corresponding to that of the molecules contained in
the most superficial lamine, so the former, however sharp
their angles or smooth their surfaces may appear, neither
their corners are geometrically angular nor their surfaces
and edges mathematically plane, but both will present in-
equalities of the same shape and size as their ultimate
molecules. This explanation of the process of crystalliza-
tion is not at all inconsistent with the fact of the expan-
sion of water prior to and at the instant of congelation, as
it is not improbable that, after a certain degree of approxi-
mation of the molecules of water, electricity is evolved,
causing at first expansion, the obvious result of molecular
repulsion, and afterwards rectilmear molecular arrange-
ment, the consequence of impulsion, this latter taking
place suddenly. The force of expansion is well known to
be very great, its total effect being probably equal to the
sum of the impulses of all the moleeules of the freezing
liquid. It is very probable that this might easily be de-
termined by experiment. I may observe that I consider
this observation as altogether unconnected with what has
been before advanced, and merely regard it as a suggestion
quite as likely to be true as any other explanation which
may have been given of this remarkable fact.

Having now discussed fully the subject of crystalliza-
tion, I shall proceed to apply the facts elicited by the dis-
cussion to the explanation of the cause of the radiated

BY MOLECULAR COALESCENCE. 53

structure of the larger globular calculi as noticed at page
30; where, as well as in other parts, it has been observed
that the globular carbonate of lime, when in small quan-
tities, exists in the form of bright, homogeneous spherules,
looking very much like globules of oil or bubbles of air,
but that, after beimg incorporated into large spherical
masses, these forms entirely vanish, and are replaced by
concentric laminze and fine lines radiating from the centre
to the circumference. The formation of the laminz has
been explained; it now remains to consider that of the
radiating lines. Now, as the explanation of all the ap-
pearances presented by these calculi has so far been
shown to be the result of attraction, it is only a fair in-
ference that these lines also are due to the effect of the
same force. But in the last article attraction has been
shown to be the direct antagonist of rectilinear molecular
arrangement; therefore an apparent incongruity arises,
which I will now explain. In perfect spheres, constructed
on the principle of universal attraction, all the molecules,
being attracted in directions parallel with their circumfer-
ence by equal and opposite forces, are as if not attracted
at all by any force acting upon them laterally ; and there-
fore the sensible effect of gravity upon these molecules
can only be exerted in one direction, that is to say,
it can only act im straight lines extending from the
circumference to the centre. Hence, such being the
action of gravity in spheres, it is clear that so far as
the rectilinear arrangement of their molecules is con-
cerned, the effect of gravity, and that of impulsion
upon them is the same. But attraction thus operating
upon these molecules does not produce perfect crystals,
nor does impulsion acting on similar molecules produce
lines like these. These lines, though presenting an im-

D4 FORMATION OF SHELLS OF ANIMALS, ETC.,

perfectly crystalline appearance, are deficient in other
characters belonging to true crystals. They are adherent
on all sides to the contiguous lines, and therefore they
have no definite form. These lines, though without doubt
present in the smaller globules, are not apparent, partly
from their minuteness, and partly from the great convexity
of such globules and the high refractive power consequent
thereon rendering their detection difficult or impossible.
Hence the cause of these mechanical conditions under
which the molecules are placed in spherical calculi, which
render it impossible that their arrangement could be
otherwise than rectiliear, bemg now shown, and the
differences between these lines and true crystals poimted
out, the seeming incongruity before mentioned vanishes,
and this circumstance itself furnishes a certain amount of
evidence in proof of the correctness of what has been
before advanced on both subjects—the formation of
spheres by molecular attraction, and of crystals by mole-
cular impulsion.

It was observed at page 40, that a separate considera-
tion would be given to a process of complete or final mole-
cular disintegration, there merely alluded to, and that
some experiments demonstrative of this process would be
described. I will therefore now proceed to consider this
subject, which I may observe is in no respects inferior in
importance to those already treated of, and perhaps in
some respects more remarkable.

ON COMPLETE MOLECULAR DISINTEGRATION.

In the explanation of the process of coalescence of two
globules of carbonate of lime into one, it was observed
that, before these globules could become incorporated,

BY MOLECULAR COALESCENCE. 55

their molecules must be displaced from the position which
they had occupied in relation to the centres of these two
spheres, and be disposed around the centre of one sphere,
containing all the molecules, which, before coalescence,
were contained in the two. This part of the process of
coalescence was called molecular disintegration. Now,
there is another case in which exactly the same physical
process takes place, but under different circumstances,
and is therefore attended with different results. This I
shall call final or complete molecular disintegration. It
would seem, on examining specimens showing this pro-
cess, to consist in the complete separation and dispersion
of the molecules of certain compound calculi, leading to
their total disappearance. But the fact is, that their
molecules, in the place of becoming, after disintegration,
collected into one large calculus, as in the disintegration
before noticed, join together to form numerous small ones
of different shapes, becoming dumb-bell ellipses or sphe-
rules, some of such extreme minuteness as only to be just
visible by the microscope. The process by which this is
effected, and the physical conditions under which it takes
place, will form the subject of the present article. It will
be seen, on referring to page 40, that the spherical figure
of the calculi, composed of a mixture of carbonate of lime
and triple phosphate, is referred to two kinds of attrac-
tion, namely, universal attraction or gravity, and that
attraction which exists in a greater or less degree in all
animal and vegetable fluids, called tenacity or viscidity,
which, for convenience sake, I have called the attraction
ot tenacity. The former of these forces, acting at sensible
distances, brings the particles of these calculi into con-
tact, that is, within the range of the attraction of tenacity,
which, acting only at insensible distances, must have been

56 FORMATION OF SHELLS OF ANIMALS, ETC.,

imoperative but for the previous action of gravity. So
that in this way the attraction of tenacity maintains a
position intermediate between an universal influence
strictly physical, and a condition of matter which seems
to connect inorganic with organic forms of existence.
The condition which I mean is that of sphericity or rotun-
dity of contour, a character which has generally been
regarded as one of the characteristic distinctions between
inorganic and organic bodies. It is also observed in the
same page, that the relative intensity of these two forces
is In proportion to the quantities of the triple phosphate
and the globular carbonate present. And, for reasons
there given, it is further stated, that the more there is of
triple phosphate combined with the globular carbonate in
these calculi, the less will be the attraction of tenacity ;
so that such proportions of these substances may be asso-
ciated in these bodies as to neutralize the force of tenacity,
in which case their molecules would be held together only
by the attraction of gravitation. It is in calculi of this
description that the disintegration in question can be best
displayed. And the experiments by which this is effected
will furnish additional evidence in proof of the principles
which have been adverted to in explaining the facts of
molecular coalescence, and of their perfect applicability to
the explanation which has been given of this process.

The following is one of the experiments which, for the
convenience of those who may wish to repeat it, I will give
in detail. Three bottles are to be charged with the two so-
lutions mentioned at page 6, and provided each with two
glass slides exactly according to the directions there given.
Then one of these bottles is to be tied over with oiled silk,
to prevent evaporation of its contents, care being taken
not to disturb the solutions. The other two are to remain

BY MOLECULAR COALESCENCE. 57

uncovered for three weeks, when sufficient of the fluid
in one of them is to be put into the other entirely to fill
it, none of the solid material being introduced with it.
These two bottles may now stand for six weeks or two
months, the one bottle bemg kept full by the occasional
addition of fluid from the other. Now, at the expiration
of the time mentioned, it will be obvious that the density
of the fluid in the bottle which had been tied over, and
from which, therefore, all evaporation had been prevented,
will be much less than that which had been kept full
by the addition of the fluid from the third bottle; and
hence the globules on the slides in these two bottles will
have been for some time under different mechanical cir-
cumstances, one set of globules having been kept in con-
tact with a fluid less dense than that m contact with the
other globules, whilst the chemical composition of these
two will be as much alike as can be under such cir-
cumstances. Any difference then which may be found
in the globules of the two slides can only be attributable
to a mechanical cause. All the solid matter must be re-
moved from the upper surface of these slides, and that on
the lower, after beimg well washed, may be examined
either in Canada balsam or in glycerine, all the slides
being treated exactly in the same manner. It will be
found, on comparing the specimens, that the globules on
the slides taken from the fluid which had not been allowed
to evaporate will be clear, with a sharp outline, and either
laminated or not, according to the quantity of carbonate
in their composition. Indeed, all the globules on these
slides will answer to the description given at page 36.
The globules on the other slides will be altered in their
structure, the amount of difference depending upon the
relative densities of the fluids in the different bottles, and

58 FORMATION OF SHELLS OF ANIMALS, ETC.,

upon the time the slides had been kept in the dense solu-
tion. ‘The full effect of this mode of experimenting can-
not be obtaimed without varying the experiment above
described, especially with respect to the time allowed for
the globules to be acted upon by the dense solution. But,
as there given, it will suffice to show some of the effects of
complete disintegration on the globules composed of triple
phosphate and globular carbonate. ‘Those composed en-
tirely of the latter component, which are situated higher
on the slide, are not in the least affected, however long
they may have been kept in the dense solution. This

process of disintegration im the former is first indicated by
the radiating lines becoming more distinct, especially
near the margin of the globules. Afterwards separations
occur between these lines, so that the circumference of a
globule, in the place of being one sharp line is made up of
their projecting ends, giving the appearance of a ciliated
fibrous zone, whose breadth depends upon the degree of
disintegration. As this process progresses, this zone dis-
appears in certain parts, leaving the periphery uneven,
and afterwards it disappears altogether, when the globule
becomes reduced in size according to the width of the dis-

BY MOLECULAR COALESCENCE. 59

integrated zone. And thus the disintegration proceeds
until the entire calculus isremoved. (See fig. 4, 4), which
accurately represents some of these globules. The disin-
tegrated molecules, deprived of the whole or a great part
of their triple phosphate, are dispersed through the solu-
tion, where some again coalesce, but into much smaller
globular and oval particles, exhibiting all the stages of
molecular coalescence described at the begimning of this
paper, while others reassume a crystalline form. Now,
in explaining the cause of this fact, I may repeat the ob-
servation, that no kind of disintegration takes place in the
globules of simple carbonate of lime on the same slide,
that is, in those globules, whose molecules are kept to-
gether in the spherical form by two attractive forces,
namely, gravity and the attraction of tenacity, but only
in those globules in which the attraction of tenacity is
neutralized by the combination of triple phosphate with
the globular carbonate; and, therefore, it can only be
with the former of these forces, namely, gravity, that
the disintegrating cause has to contend; and as the
conditions of the experiment are such as to exclude the
action of all other forces upon these calculi, excepting
that of gravitation, it must follow, of necessity, that
gravity is the disintegrating agent. And, moreover, as it
was shown that these calculi are formed by the force of
gravitation drawing their molecules towards their centres,
so it must be inferred, that the same force, in producing a
directly opposite effect on these caleuli—their disintegra-
tion or destruction—will draw their molecules from their
centres. In this experiment it is evident that the sur-
rounding dense medium would act in this manner, attract-
ing the molecules of these bodies with a force exceeding
that by which they are attracted by the bodies themselves.

60 FORMATION OF SHELLS OF ANIMALS, ETC.,

Hence we arrive at a most important physical fact, namely,
that spherical bodies, formed on the principle of universal
attraction in a medium of given density, become, in one
of greater density, gradually disintegrated, and _ their
molecules, at first completely separated, afterwards re-
arrange themselves in fresh forms.

The experiments next to be described, showing the facts
of molecular disintegration, have been given already, in
the ‘Transactions of the Microsopical Society,’ published
in the January number of 1858 of the ‘ Quarterly Journal
of Microscopical Science.’ These facts can be demonstrated
in a description of artificial calculi presenting characters
different im some respects from those already described.
They may be prepared by dissolving one pound of gum
arabic in two pints of water, and straining the mucilage
through a fine hair-sieve, and then putting one pint of
the solution, with two ounces of carbonate of potash well
mixed together, into a quart bottle, after twenty-four
hours adding, by means of a syphon, the other pint of
mucilage, and after that leaving the bottle at rest for six
weeks or two months, when the calculi will be found ad-
herent to its sides, or in the fluid at the surface. Besides
these calculi of different degrees of solubility, crystals
are formed in these solutions; some consist of bicar-
bonate of lime, formed by the free acetic acid in the
mucilage combining with a portion of the potash, and
setting free carbonic acid, which, uniting with some
of the carbonate of lime, forms a bicarbonate. These
crystals, being sparingly soluble, remain in the solutions,
and chiefly on the surface. I may observe, that in a
solution of gum all crystals produced by double decom-
position, which do not combine chemically with it, are
large and well-formed. Hence such a process may be

BY MOLECULAR COALESCENCE. 61

taken advantage of to crystallize salts, otherwise difficult
of crystallization. The calculi formed according to this
process are very large, being ;5th or jth of an inch in
diameter, and spherical, excepting when they adhere to the
side of the bottle, in which case they are flattened on the
side attached. They are very regularly and beautifully
laminated, and coalesce in the same manner as those above
described. When treated with weak acetic or muriatic
acid they effervesce, and leave a residue of amorphous
matter. When dried they retain their globular figure,
but show a tendency to split into segments ; their surface
is white, and generally smooth, but they do not present
that glassy or pearly appearance which is remarkable in
those prepared by the other process. Under polarized
light they present a distinct cross, and appear somewhat
coloured; but do not exhibit the prismatic colours distinctly,
like the other calcul. The most remarkable property of
these calculi is the facility with which they undergo either
partial or complete disintegration. So that they cannot
be put up as transparent objects permanently, in any watery
fluid. In glycerine they disappear after a few weeks,
leaving sometimes a residue having the form of a thin
membranous capsule. If heated a little, and then put into
hot oil, they first become covered with a feathery coating
and afterwards fall into large fragments. This coating
seems to me to be produced by their separating the oleine
from the stearine, absorbing the one and leaving the other
on the surface. But their most smgular property is the
partial disintegration which they undergo when removed
from the bottle in which they were formed, and put up in
a cell filled with the solution taken from the same bottle,
and so secured from the access of air that no alteration in
its density or chemical composition can take place.

62 FORMATION OF SHELLS OF ANIMALS, ETC.,

In this case all the carbonate separates from the vegetable
basis, and becomes collected into small globular particles
of different sizes, mixed with crystals of carbonate of lime.
These are scattered about the vegetable residue, which
retains the place, figure, and laminated appearance of the
original calculus, but when examined by polarized lhght
exhibits no trace of earthy carbonate ;.excepting im the
centre of each circular portion of residuum, there are two
imperfectly-formed crystals joined together, and presenting
somewhat the appearance of nuclei in process of division.
I have specimens of such calculi, which have been in
solution of gum for about nine months. It may not be
irrelevant to state that these experiments and examinations
have not been hastily made, or made only on scanty
materials, but have been repeated over and over again
with due care and attention to everything at all likely to
affect the results. In considering the cause of disinte-
gration as displayed in these calcul, it may be observed,
first, that their structure is less dense, as shown by the
absence of transparency observable in the other calculi ;
and, secondly, that insoluble vegetable matter enters
largely into their composition. <A part of this matter may
have been suspended in the solution of gum, which had not
stood sufficiently long to allow of its complete subsidence ;
but I believe the principal part of it is set free durmg the
decomposition of the salt of lime contained in the gum,
which, bemg then placed under circumstances particularly
well fitted for the production of large calculi (the experi-
ment being performed on a large scale), combines mole-
cularly with a small portion only of the carbonate of lime,
to form the calculi in question. ‘The other portion of the
carbonate of lime, combining with the gum, forms the
same description of calculi as those formed of carbonate of

* BY MOLECULAR COALESCENCE. 63

lime by the first process. Hence it is evident that calculi
thus composed of very dissimilar substances, held together,
as is clear from their structure, by only a feeble attractive
force, must owe their spherical figure chiefly to gravity.
Consequently, when removed from the bottle in which they
were formed—where all the molecules entering into the
structure of each calculus would have been exactly balanced
between the mutual attractions of the molecules themselves
and that exerted upon them by the various parts of the
bottle—to a small cell of glass, where they will be brought
into much closer contiguity with surrounding objects, this
balance will of necessity be destroyed, and the molecules
being now attracted by the surrounded substances more
forcibly than by one another, their separation will ensue.
The vegetable component molecularly united with the
carbonate of lime being exquisitely delicate, and conse-
quently very light, as experiment shows, retains its form
in consequence of its attraction of tenacity (which, how-
ever, is only very feeble), being greater than the attraction
of gravitation exerted upon it by surrounding objects,
which attraction, considering the extreme tenuity of this
residuum, can only be very feeble. And the earthy
particles composing these calculi, being attracted by one
another more forcibly than by the molecules of the
vegetable residuum, become separated from it, and coalesce
into globules. Now, as this explanation is perfectly in
accordance with the laws of gravity and the attraction of
tenacity, and as the conditions under which they act are
within the reach of experiment and the results determinable
by microscopic examination, it may be affirmed with cer-
tainty that these forces would act as here shown. Hence
there only remains one point to be determined, and that is
the adequacy of these forces, under the present conditions

64 FORMATION OF SHELLS OF ANIMALS, ETC.,

to produce the effects attributed to them. Now it may be
observed that, as in this case there are no other known
causes capable of producing such effects, unless it can be
supposed that vitality has produced them, the simple fact
itself of their being produced under such circumstances is
the best proof of their adequacy to produce them. I have
dwelt longest upon the results of this experiment, as
probably they will be considered the most remarkable of
all that have been described, although I must say that
there is nothing wonderful in the facts here stated respect-
ing these calculi, or in the explanation of them just
advanced. It is only what might have been anticipated
under such circumstances, being only the necessary conse-
quence of an ordinary and universal cause.

There is yet one more case of final molecular disinte-
gration, which differs in some respects from those just
described. The experiment required for its demonstration
simply consists in taking two slides from a bottle in which
they had been kept for three weeks, according to the
formula and directions given at page 6; and then, after
removing the carbonate deposited on their upper surfaces,
and washing the lower ones with distilled water, without
removing any of the carbonate, introducing these slides,
with the coated surfaces inclining downwards, into another
bottle contamimg solutions the same in quantity and
density as the first, and treated in the same manner, so
as to have a second deposit on their lower surfaces. After
a month or six weeks these slides are to be removed from
the bottle, the carbonate removed from the upper surfaces,
and the lower ones washed with distilled water, and then
examined in glycerine or Canada balsam. The globules
adherent to the lower surfaces of these slides will be of
various kinds. A few formed from the last solution will

BY MOLECULAR COALESCENCE. 65

have the ordinary characters, but those formed of particles
from both solutions will differ considerably. Some will
retain the form which they had on removal from the first
bottle, but their transparency will be impaired, partly
by the addition of fresh particles, partly by their former
molecules having become confused and made to present
a dusty appearance; some will appear distinctly lami-
nated, the laminz being separated by dark amorphous
Imes; a third set appear to be globular instead of flat,
and to be filled with air and amorphous molecular
matter. Several of each kind will be seen in different
stages and degrees of disintegration, mouldermg away
as it were; and of a few merely circular circular traces
will be left on the glass, almost invisible under ordinary
illumination, but by polarized light distinct, exhibiting

cross, but no colour, excepting a very faint blue. In this
ease the disintegration is not confined to the calculi com-
posed of a mixture of triple phosphate and globular
carbonate, but it affects equally those composed of the
latter compound, whether large or small. Now, on con-
sidering the conditions of this experiment, and comparing
them with those of the preceding ones on molecular dis-
integration, it will be obvious that these effects can only
have been produced by one cause, and therefore admit
only of explanation on one principle. Difference in den-
sity of the solutions in which the perfectly formed glo-
bules were immersed, as in the first experiment, can have
had no share in producing it, any peculiarity in the com-
position of these globules, as in the second experiment,
can have had nothing to do with it. And as the solutions
were, in both stages of the process, exactly of the same
composition, these changes in the structure of the glo-
bules after the second immersion are not the effects of

5

66 FORMATION OF SHELLS OF ANIMALS, ETC.,

chemical action. Hence they can only be attributed to
the molecular disturbance of the previously arranged and
balanced molecules by the sudden addition and contact
of fresh ones. This is no more than might have been
expected ; indeed, it could not have been otherwise, if the
cause on which the globular form of these bodies depends
be the force of gravitation, and if the explanation given
at the beginning of this paper be correct. One result of
this experiment, the dusty appearance in the interior of
many of these globules, arising from the disturbance and
loss of balance of their molecules, shows that light is only
perfectly transmitted by these spherical bodies when their
molecules are arranged and adjusted on physical prin-
ciples, and, therefore, that the forces by which their
perfect balance is maintained are in some way connected
with the propagation of the etherial undulations upon
which light is supposed to depend, molecular confusion
and opacity being the effects of the same cause. This
fact is apparent in the form of disintegration preceding
coalescence, as shown by the central opacity of incom-
pletely formed globules, but it is much more strikingly
displayed in the globules formed in this experiment. Also
another fact is made by this experiment particularly pro-
minent, which is the necessity of time in the operation
both of coalescence and disintegration. In the formation
of globules according to the ordinary process of coales-
cence, everything takes place gradually ; the decomposi-
tion, and consequently the formation, of the globular car-
bonate being slowly effected, and the globules bemg slowly
attracted towards one another, as can be shown by the
microscope ; so that sometimes three globules lying near
together can in some specimens be seen to have changed
their shape before they are actually brought imto contact.

BY MOLECULAR COALESCENCE, 67

In this second process, on the contrary, a large quantity
of globules and globular particles are brought suddenly
into contact with those already perfectly formed. The
balance and with it the condition of stasis of their mole-
cules is destroyed, and the globules thus circumstanced
ceasing to be attracted to one centre, go into fresh globular
forms, much smaller and less regular than those produced
in the first stage of this experiment, and thus for a time
nothing but molecular confusion results.

Ultimate molecules or atoms being frequently men-
tioned in the course of these observations, these researches
will not be complete without some some notice being
taken of the probable form which matter had when it first
came into being, or which it now has when it comes into
existence in a new state of combination. As such exist-
ences are invisible under the highest magnifying powers,
all observations on their size and shape must be specula-
tive. Two opinions, however, have prevailed with respect
to their form. Haiiy and others have adopted the notion
that they are all angular, while Hooke, Wollaston, and
other more recent writers, have assumed that they are of
a rounded form. Now, as respects my own view upon
this point, I may observe that it has been shown—I think I
may say demonstrated—that matter, immediately it comes
into existence in some new state of combination, assumes
one or other of two forms, according to the predominant
force acting upon its ultimate molecules. If that force be
attraction, the first forms are curvilinear; if impulsion,
they are rectilmear. But I am aware that these first
forms, bemg made up of alternate particles, are not them-
selves atoms or ultimate molecules. Now, in order that the
first portions of matter may have a definite form, they must

68 FORMATION OF SHELLS OF ANIMALS, ETC.,

either come into existence in separate places or at sepa-
rate times, that is, they must not be within the sphere of
each other’s attraction or impulsion, for they would then
be formed into globules or crystals before they had time
to acquire their specific form. Now, as no experimental
or natural process can be conceived by which a molecule
is formed alone, this condition seems to be impossible.
Hence, so far evidence is opposed to the views of both
these classes of philosophers, and the probability seems
more in favour of an amorphous condition of matter prior
to its arrangement into globules or crystals. But, fur-
thermore, if attraction and impulsion are the forces to
which all the known and appreciable forms of matter are
due (and the correctness of this supposition, especially as
respects attraction, no one doubts), then, if the component
molecules making up these forms have themselves a defi-
nite form, whether angular or spherical, or some modifi-
cation of these, some unknown force or forces must have
exerted a prior influence upon them, affecting each mole-
cule separately—something in the same way as gravity
and impulsion have been shown to affect them collectively—
or these molecules must have in themselves the power of
giving themselves a form. Now, as there is no evidence
of any such force or of such an inherent power in matter,
the idea of a definite form of the nascent particles of
matter is unsupported by any kind of proof, and therefore
is entirely untenable; and the only inference is, that when
matter first comes into existence in some fresh state of
combination, as, for instance, carbonate of lime combined
with a viscid substance, it has no definite form until
gravity has given it one. As respects the size of atoms, it
may be observed, that as the attraction of gravitation is
exerted upon matter directly in the ratio of the quantity,

BY MOLECULAR COALESCENCE. 69

and as this force cannot act effectively upon it until its
vis inertie is first overcome, it is perfectly conceivable that
the quaytity of matter, when coming into existence, may
be so small as to be affected more by imertia than by
gravity or impulsion, and may thus remain for an instant
undetached from the surrounding material substances, until
the quantity becoming augmented sufficiently to cause its
removal by the action of the predominant physical force,
it becomes detached as a part of a crystal, or a part of a
sphere, according to the nature of that force, whether it be
attractive or impulsive; and hence the size of this particle
may easily be imagined to vary, that depending partly
upon the intensity of the physical force and partly upon
the nature of the matter acted upon; but its form, not
being necessarily either spherical or rectilinear, must, for
the reasons just given, be uncertain; consequently, it may
be inferred that all molecules are amorphous, and that, if
there ever was a period when matter existed unacted upon
by attraction or impulsion, it must have been in a chaotic
or amorphous state—a something “without form, and
void.”’

PHYSIOLOGICAL PART.

Havine in the preceding pages considered, somewhat at
length, the mode of formation and the structure of
calculi artificially prepared, the subject of crystalization,
and the process of final molecular disintegration, I shal]
now proceed to apply the facts elicited in the course of
these inquiries to the explanation of the analogous forms
of carbonate of lime, as they are found in organized
bodies.

I shall first consider the perfect similarity as to structure
which exists between the artificial and natural products ;
and then consider the identity of the laws under which
both classes of substances are produced; after which I
shall show, that the same physical laws of formation
extend to other natural structures, both animal and
vegetable. But as my time will not permit of more than
a limited application of these laws to organized structures,
I shall chiefly confine my observations to the structure
and formation of shells and bone, the mode of formation
of pigment and some other cells, and the structure and
development of the crystalline lens. It may be observed
that, as the natural products will be shown in the following
pages to have been formed upon precisely the same phy-
sical principles as the artificial ones, and as it is in the
latter only that their mode of formation admits of being

MOLECULAR COALESCENCE. 71

investigated experimentally, and the physical principles
concerned in their formation clearly and rigidly demon-
strated, it will be necessary, for the full comprehension of
the physiological division of this paper, that the physical
part should have been carefully considered, and generally
understood. As in the physical part of this paper I have
described minutely the different processes for making
artificial calculi, and the mode of performing all the
necessary experiments, in order that those who wish to
prepare their own specimens may be able to judge for
themselves of the truth and accuracy of the various state-
ments contained in these accounts, so in the physiolo-
gical part I shall also adopt a parallel course of procedure,
by describing the mode of examining the natural structures,
and pointing out the parts best adapted for displaying the
various stages of their development. This has been espe-
cially neglected in the examination of calcareous tissues, thin
sections being too exclusively employed for that purpose,
which, although they display well the number and arrange-
ment of the lamine of perfectly formed parts, and so far
are indispensable, yet shows little or nothing of the earliest
forms of the earthy deposit, especially as this is all re-
moved by the subsequent grinding, unless care be taken
to prevent it. Nothing can be more dissimilar in appear-
ance than the different forms assumed by the globular
carbonate of lime in the various parts of the same shell,
and it is only by examining the passage of the one form
into the other that their identity can be determined.
This observation strikingly applies to the analagous forms
of the artificially prepared compound of the same compo-
sition, in which, as in the natural products, there are the
molecular, globular, and laminated forms, resembling one
another in no respect excepting in their composition.

72 FORMATION OF SHELLS OF ANIMALS, ETC.,

The first of the natural products which I shall consider
are the minute calculi found in the urine of the horse.
As these structures are well known to microscopists,
it will not be necessary to describe them. It may
suffice merely to say that calculi of a similar composition
can be formed artificially, so exactly resembling these as
not to be distinguished from them by the most careful
microscopic examination. Those artificial calculi, the
most like the calculi found in the urine, are the calculi
deposited in the bottle, and not those adherent to the
lower surface of the glass slide. (See the account of the
process for making artificial calculi.) These natural
calculi also, if examined in a good specimen containing
calculi of various forms and sizes, will be seen to present
appearances indicative of coalescence, in all respects the
same as those of the analogous forms of the artificial
calculi. These urimary calculi, existing in a fluid excreted
from the blood by -a living organ, are considered by
physiologists to be vital products. It is observed in a
review of Professor Quekett’s ‘ Lectures on Histology,’ that
“ henceforth a calculus will not be regarded as merely a
mass of earthy or crystalline matter, collected by simple
attraction of aggregation; but it shows evidence of the
existence of cell-formation.” Professor Quekett also
observes, concerning these calculi, that they are not mere
sediments, but are passed from the kidneys, being either
made up of small calculi, or of concentric laminz ; being
in fact urmary calculi in miniature, the secreting cells
remaining after the calcareous element has been dissolved,
as in the larger calculi; and that a calculus found in
connexion with the body is not a simple mass of inorganic
substance, containing organic matter as an accidental
constituent, but that a calculus, when in contact with

BY MOLECULAR COALESCENCE. 73

living tissues, may, like shell, have life, and with it the
power of growth or development; the secretion serving
as the blastema or pabulum from which the cell-
contents are derived. Professor Quekett adds, that he
would not assert positively that such is the case, but
when the subject is carefully considered, ‘it has the
appearance of truth on its side.” I may observe that by
this allusion to Mr. Quekett’s lecture, I do not necessarily
refer to him as the originator of these views, whether they
be true or false, but I have merely quoted this lecture as
showing his opinion upon this subject, an opinion which,
from Mr. Quekett’s high position and very extensive know-
ledge of histology, I consider to be the one most generally
entertained, at least in this country, where the cytoblast
theory of Schwann is carried to its greatest extent.
Now it may be observed, that as these calculi are formed,
as Mr. Quekett has noticed, in connexion with the body,
or at any rate they are found in a fluid which has pro-
ceeded directly from the blood, it is impossible to prove
that they are not of vital origin. The cell theory is
altogether in favour of this view; for nothing can appear
more probable than that a cell-germ, having escaped from
the blood into the pelvis of the kidney, should afterwards
be carried with the urine into the bladder, where, in-
creasing and multiplying by the exercise of its own
inherent vitality, it should grow, at the expense of the
secretion containing it—this serving as its blastema—into a
calculus; hence this question, like most other pathological
and physiological ones, can only be decided by the com-
parison of evidence adduced on both sides. As in the
discussion of this and other questions I shall frequently
be obliged to refer to the cell-germ theory, I think my
observations will be better understood if I at once

74 FORMATION OF SHELLS OF ANIMALS, ETC.,

avow my opinion upon this point; and, therefore, I
may briefly notice, that although I partially admit many
of the facts connected with the general structure of
cells, such as an exterior investment, or, as it is called,
a cell-membrane, cell-contents, and very frequently
a central part, differmg from the rest, called the
cell-nucleus, I am not of opinion that these parts are
endowed with a distinct and separate vital power, by
which one cell can act independently of another and of
the surrounding parts, and grow and multiply by the
exercise of its own individual vital endowments. I wish
particularly to notice also, that my object in bringing
these researches before the public is not to attack the
cell theory, but that it is to explain certain facts which
have come under my notice, and that I wish to deal only
with facts, and such deductions from them as the facts
themselves will be shown to justify. Notwithstanding, as
it must sometimes occur, that the decision of a doubtful
question will depend upon a comparison of evidence, it
will be impossible to avoid making allusions to the
opinions and views of others. But to return to the
subject of the formation of these urinary calculi, I may
notice that, if the cell-development theory be tenable in
any case of the formation of adventitious structure, it is
so in this. It is true that, in this instance, the connexion
between the living structures and the adventitious pro-
ducts is not so clear as in many others, but still it may be
assumed that it did once exist, but that now it has ceased;
however, that there still exists sufficient connexion be-
tween them, through the medium of the urime acting as a
blastema or pabulum, to furnish the cells with the requi-
site supply of material for their individual growth and
multiplication. Such, in substance, is the explanation

BY MOLECULAR COALESCENCE. ad
®

which has been given of the formation of these bodies,
and nothing can be more plausible and apparently correct,
if only the foundation upon which it rests is solid. The
question on the other side is, can any other explanation
of the same class of facts, equally plausible, be given. To
this question it may be replied, that no other explanation
which suits so completely all the circumstances of the
case can be advanced, without removing entirely the foun-
dation upon which this one is built. The following ex-
planation of the manner in which these calculi are formed,
unconnected altogether with the hypothesis of cell-growth,
and in accordance with facts as shown by experiment, is
deduced from the comparison of the results of the artificial
process for making calculi with those of the natural pro-
cess. As there can be no doubt but that the ure of the
horse, when recently secreted, contains in solution som®
compound of lime, albuminous matter, and some salt of
urea, easy of decomposition, and when decomposed, fur-
nishing carbonate of ammonia; it is obvious that, as soon
as this decomposition of the urea or its salts commences,
all the conditions necessary for the formation of the
globular carbonate of lime specified in the artificial pro-
cess are brought into existence. The carbonic acid set
free by the decomposition of the carbonate of ammonia
would combine with the lime, displacing the acid before
combined with it, to form a carbonate of lime, which,
meeting in its nascent state with the albumen, would form
with it the globular or coalescing compound in question,
the particles of which, being suspended in a fluid medium,
holding animal matter in solution, would coalesce to form
globules of various sizes and degrees of perfectness, accord-
ingly as all the other conditions prescribed in the artificial
process were more or less favorable for the process of

76 FORMATION OF SHELLS OF ANIMALS, ETC.,

coalescence. Now, as in this case there appears to be
no reason for assuming the absence of any one of these
conditions, and as it is certain that, if all the physical and
chemical means employed in the production of artificial
calculi are the same in this—the natural process—as in
the artificial one, the result will be the same also. There
seems to be no reason why this explanation of the forma-
tion of these urinary calculi should not be regarded as
the correct one. Vitality has not been named as having
had any share in the formation of these natural products.
Nor, as it has been demonstrated that bodies in all
respects analogous to these calculi can be formed without
any possible vital interference, does there appear to be
any necessity to attribute any part of the formation of
these urinary deposits to the influence of “ vital forces,”
or to cell-development. At any rate it is certain, that if
vitality does contribute anything to their production,
the fact of the perfect resemblance between these calculi
and the artificially formed products proves that this con-
tribution is so small that it might have been altogether dis-
pensed with. There is one fact connected with this subject,
which has been regarded by physiologists and histologists
as furnishing conclusive evidence in proof of the vital
origin of these and similar natural products, which is
that of a soft material— animal basis” —being left after
the decalcification of these products by the action of hydro-
chloric acid, of the same form, and with markings similar
to those which these products had before bemg thus
treated; but as exactly the same effect is produced by a
like treatment of artificial calculi formed in a solution of
albumen in the place of gum, this can no longer be con-
sidered as an infallible test of an organic formation. This
residuum in the case of the natural products is regarded

BY MOLECULAR COALESCENCE. Vi

as the secreting cell deprived of its calcareous element.
These calculi can be made by mixing with one portion of
white of egg a very small quantity of muriate of lime,
and with another portion of the same a little sub-car-
bonate of potash or soda, and then putting them together,
without mixing them, into a bottle, into which two glass
slides had been previously introduced, as in the process
with the gum, and then keeping the bottle at rest for
two or three weeks. This experiment must be made in
cold weather, as the albumen rapidly decomposes. In
examining these calculi for the purpose of seemg the
albuminous residue, corresponding to the “ animal basis ”
before mentioned, they should be examined on a micro-
scopic slide, with a piece of thin glass over them at the
time the acid is in action, which ought to be very weak,
so that in the partially decalcified globules the perfect
parts and the decalcified ones may be seen at the same
time, and compared one with the other. The polariscope
will be necessary in this examination. After all the cal-
careous matter has been removed, the residue will be seen
to be of the same size and with the same appearance of
lamination as the original globule ; but these will of course
be fainter and invisible under perfectly polarized light,
showing that during the formation of calculi of this kind
the albumen becomes solidified and molecularly blended
with the carbonate of lime. This fact proves also, so far
as it goes, that soft matter is as much under the influence
of physical agency as hard matter, provided only the me-
chanical conditions under which both are placed when
acted upon are the same. I may observe, in concluding
the remarks upon these calcul, that my conviction of the
correctness and truth of the explanation here given of
their origm and mode of formation, as opposed to the

78 FORMATION OF SHELLS OF ANIMALS, ETC.,

physiological explanation, is so strong, that I cannot help
believing that, if only it had been earlier known that
bodies exactly like these calculi could be prepared arti-
ficially, and also all the conditions known under which
the process is conducted, the opinion that they are orga-
nized structures would never have been started; and
therefore, if my view is the correct one, as I have no doubt
it is, I claim no credit on that account, or attribute any
want of penetration to those who have entertained a dif-
ferent one, seeing that I commenced the investigation of
this subject under advantage which they had not.

The next subject which I shall investigate will be the
structure and development of the shells of animals.
I shall make choice for examination of those which are
most common, and therefore can be most easily obtained.
I shall begin with the external skeleton, or, as it is com-
monly called, the shell of crustaceans, and, first, shall
consider those membranous parts which are connected
with or which make up part of the shell, but only so far
as the process of calcification or the development of shell-
tissue is concerned. I shall then examine more particu-
larly the arrangement of the different structures, as they
are found in the different parts of the completely formed
shells of this class of animals.

All the parts of the ordinary crustaceans, as, for instance,
the lobster, which contain a large quantity of earthy
matter in their composition, cannot be considered as
pertaining to the skeleton, the carapax and some other
parts being more analogous to integument in the office
which they have to fill, and the parts called apodemata,
affording attachment to muscular fibres, perform the

function of bone, whilst others similarly related to muscle

correspond to the osseous tendons of birds.

BY MOLECULAR COALESCENCE. 79

I shall consider all these parts separately, in the order
I have named them. And first, the tegumentary part of
the shell, which is made up of alternate layers of hard and
soft tissue, very closely connected together, especially in
the more superficial regions of the shell. The intimacy
of the connexion of these layers differs in different crus-
taceans, and in different parts of the same shell. In some
they are so blended together as not to admit of the
slightest separation, excepting on the surface next to the
animal. The first or deepest layer consists entirely of
branched pigment-corpuscles. This‘is absent in the
shells of many crustaceans, and therefore is not an essential
part of shell-tissue. The next layer is a thin and almost
transparent membranous layer, of a glassy appearance,
and of rather a dense structure; connected on its deep
surface with the pigment-layer, and by its superficial one
with a layer of similar structure, sometimes several such
layers may be found connected together. It is between
these layers that the calcareous matter is deposited ;
beginning on that surface of the deepest of these layers
which is furthest from the branched pigment-corpuscles.
The carbonate of lime here deposited is in extremely
small particles, presenting when out of focus the appear-
ance of minute points or perforations, dispersed more or
less thickly over the membrane, though sometimes
collected in groups, and at others arranged in lines. This
deposit I have never found on the deep surface of the
first layer, and sometimes two or three membranous layers
intervene between the earthy deposit and the pigment-
membrane. The particles of carbonate of lime as thus
deposited, are sometimes too minute sensibly to polarize
light; and in this case their composition can only be
determined by the action of weak hydrochloric acid upon

80 FORMATION OF SHELLS OF ANIMALS, ETC.,

them whilst they are under examination by the micro-
scope, the escape of gas, as seen passing from them,
indicating the presence of one of their components—
carbonic acid. After thus acted upon, as was noticed of
the artificial analogous form of carbonate, they leave a
residue of soft material— animal basis’’—of the same
shape and appearance, but much less distinct. On the
membranous layer next to this, and on those still nearer
to the surface, these particles can be seen in every stage
of coalescence, presenting so exactly the appearance of
those on the slide*employed in the artificial process, as
not to admit of beimg distinguished from them. The
resemblance between these and the artificial products is,
in some respects, more complete than between the latter
and the urinary calculi of the horse. In the shell all the
different forms and stages of coalescence are better marked,
and therefore more distinct than in the calculi from the
horse’s urine; and in those of the shell, which are not so
well marked as the artificial ones, it will be evident that
the process of coalescence has been interfered with by the
mechanical causes, and that just in proportion as in their
formation they can be seen to have been exposed to me-
chanical interference from the contiguous structures, so
do they suffer distortion and become less like those pre-
pared artificially. Consequently, the smaller these glo-
bules are, the more exact is their resemblance to the
artificial ones of the same size. By varying the artificial
process also, the less perfect forms of the natural products
can be accurately imitated. See fig. 5, which is an accu-
rate representation of a portion of the innermost layer of
the shell of a very young lobster, about four mches in
length, in which globular particles, of various sizes and
in all stages of coalescence, are shown. In the shells of

BY MOLECULAR COALESCENCE, 81

the smaller crustaceans, as in the shrimp and the prawn,
especially the latter, (if only at a proper season) in which
there being a larger proportion of the softer constituents,
and where consequently the process of coalescence is less
interfered with, the globular form of the carbonate of lime
can be seen very satisfactorily.. In these animals, mixed
with the spherules, there are sometimes circular discs,
containing in the centre smaller globular particles, and a

the circumference larger ones jomed together, so as to
present a bright crenate border. There are also patches
of these bright globular particles arranged in a stellate
form, assuming more of a crystalline character than in the
dises. All these appearances can be best observed by
merely cleansing the shells in water, and examining them
in glycerine. Grinding is unnecessary and injurious.
6

82 FORMATION OF SHELLS OF ANIMALS, ETC.,

Polarized light is indispensable im the examination of
these objects, for in some instances, as in the young
hermit crab, at the part where the calcareous and mem-
branous portions of the shell are continuous, the circular
forms of globular carbonate are so delicate that no evi-
dence whatever of its presence can be detected under the
most powerful lenses, and with the best illumination, but,
with polarized light it is brought out most distinctly.
The relative position of the molecular, globular, and lami-
nated forms of this substance, can be well seen in vertical
sections of the shell of the ordinary sized crab and lobster.
In the crab the part of the shell which supports the nippers,
and in the lobster the claws, answer very well for this purpose.
But in grinding these parts great care must be taken not
to remove the deep layer, which being the softest is gene-
rally the first which is ground off. In the sections which
I have examined, where this caution was not attended to,
all the globular layer has been removed. On examining
with the naked eye the internal surface of the portion of
the shell of the crab just mentioned, two parts are to be
noticed, a smooth and a rough one. In the former the
globular carbonate is seen in the thin vertical sections,
chiefly im one deep layer of nearly the same thickness.
In the latter, portions of globular carbonate pass at
certain points through the entire thickness of the shell,
from the deep to the superficial surface. Sections should be
made of both of these, and ground down with the precau-
tion above mentioned, and afterwards put up in glycerine
or Canada balsam. There are in all shells whose thickness
is considerable irregular passages, extending from the
deepest membranous layer to the free surface of the shell.
These passages are best seen in vertical sections of decal-
cified shells, im consequence of being obscured in the

a i Ce oman

BY MOLECULAR COALESCENCE. 83

perfect shell by the globular carbonate of lime by which
they are more or less surrounded. In the claw of the
lobster the globular and laminated forms of the carbonate
of lime are much less regularly disposed than in the crab
but in good specimens of both the deepest layer contains
very good examples of globules of carbonate in their
several states of coalescence. I have in my possession
specimens of vertical sections of lobster-shell, showing
globular particles of various kinds, resembling, in all
respects, the artificial globules, and not distinguishable
from them even by the aid of the microscope and polarized
light. Thin vertical and horizontal sections of the claw
of a craw-fish, about three or four inches in length,
or of a very small crab, examined in glycerine, are well
adapted for displaying the process of development of shell.
External to the membrane lining the cavity in the claw of
such a crustacean, the particles of carbonate of lime coa-
lesced into globules of different sizes may be seen to be
collected together in one layer. The globules composing
this layer being joined together only by their contiguous
sides, present, by their unattached portions, undulating
borders, partaking of the general form of the claw; one
border being parallel with its cavity, from which it is
separated by the deepest layer of membrane, and the other
being parallel with the surface of the claw. I may observe
that this is the general form and disposition of the coa-
lescing globules, but it may be variously encroached upon.
in different parts of the substance of the shell by small
‘circular groups of coalescing globules, which have no
connexion with the cavity of the claw, the convexity of
these groups being turned towards this cavity, so that the
radiating fibres of which the individual globules are made
up being all directed towards its concavity, that is, from

84. FORMATION OF SHELLS OF ANIMALS, ETC.,

the cavity of the claw, could have no communication with
this cavity analogous to that of the fibres of dentine with
the cavity of a tooth. As the development progresses,
the globules loose their bright and structureless character,
and begin to present laminze and radiating lines, just as
the artificial calculi do. The lines, as stated of disin-
tegrating globules, being most distinct when the globules
are suffering disintegration, will be seen best in the layers
remote from the cavity of the claw, that is, nearer to the
surface, where the softer component of shell is in excess,
These lines are the radii first of small circles, then, after
the smaller globules have coalesced, they become so
arranged in respect to the globule resulting from this
coalescence as to be the radii diverging from its centre ;
and so they continue, as the coalescence advances, to
become progressively the radu of larger and larger circles,
until at length, when this process is completed, they
remain as the radii of a circle, whose centre is that of the
part around which all the now completely coalesced
portions of globular carbonite are situated. This,
through the tendency of these lines, will be interfered with
in a variety of ways and by a diversity of mechanical
causes, So as to prevent the figure in any part of a shell
from ever becoming perfectly circular; hence these lines
will remain as the radii of a complex curvilinear form,
whose elements are too complicated ever to admit of being
mathematically determined. See fig. 5 a, which represents
a vertical section of calcefying crab-shell. The lines in these
shells, as im the case of those of the laminated artificial
calculi, are generally continued uninterruptedly from one
layer to another, so that they can be traced from the super-
ficial surface of the claw to the deep one; but it must be
observed that their distinctness diminishes towards its

BY MOLECULAR COALESCENCE. 85

cavity, where they degenerate into mere dots; and,
furthermore, that their course is sometimes undulating,
or, where the lamine join, interrupted, this depending
upon the completeness of the coalescences of the car-
bonate of lime in the part of the shell examined,
Fig. 5 a is a representation somewhat diagrammatical of
a thin section of shell, in which the lamelle and

Fig. 5 A.

| rN
BIN" un

il TO
yi Menminel AN m
: nH AN ne

Nu | iN ay TL nu

1 “ a i
(Sut
\ \ A am ea na

Ral

heh a itt an Si]

ua oe N “ ie i‘
* Sonu ;

radiating fibres appear as two sets of undulating lines |
one set, called by the physiologists lines of growth,

corresponding to the lamell of the artificial globules
running more or less parallel with the surface, the
other set corresponding to the radiating lines of the
artificial globules, passing from one surface of the shell to

86 FORMATION OF SHELLS OF ANIMALS, ETC.,

the other. These lines exist in all parts of the shell of
crustaceans, if only of sufficient thickness ; as, for instance,
in those embedded in muscular fibres, in which they can
have no communication with any cavity, so as to make
them analogous to the fibres of dentine; but they are
merely, as in the artificial products, indications of the
directions in which attraction is exerted, with variable
effect, upon the rows of molecules, producing alternate
lines of strong attraction and feeble attraction, or of
strong cohesion and weak cohesion; and thus this kind
of arrangement of the molecules of carbonate of lime is
altogether unconnected with any particular or specific
function performed by the shell, as shown by its existence
in all parts of it—the horny, as well as the calcareous—
and where the shell answers altogether different purposes,
as, for instance, where it serves for a covering and where
it answers the purpose of bone; but these lines are merely
the necessary consequence of the manner in which shell is
formed, and, under such circumstances, could not have
been otherwise. Dr. Carpenter observes, that “the
calcareous layer of the crab-shell is composed of a sub-
stance exactly analogous to ivory, being very transparent,
and apparently homogeneous, when cut into very thin
slices, and being perforated by an immense number of
minute sinuous tubuli, which run nearly parallel to one
another, from one surface of the shell to the other. This
arrangement may be seen by making a thin section of any
part of the shell; but it may be shown particularly well in
the end of the claw, which is thicker and of denser
texture than the rest. A transverse section of this shows
the tubes radiating from the central cavity towards the
external surface, and would, I feel assured, be regarded by
the most experienced observer as the section of a tooth, if

BY MOLECULAR COALESCENCE. 87

he were not informed of its real nature.” The resemblance
between dentine and crab-shell, as observed by Dr.
Carpenter, is in most respects correct, and sufficiently
striking to justify the inference that they are formed. in
a similar manner. ‘This, I believe, is the general opinion
of physiologists. The globular particles of carbonate of
lime in shell are doubtless analogous to the globular den-
tine in teeth, and the apparent spaces between the radi-
ating lines in the former correspond in a great measure to
the so-called dentinal tubes im the latter. But respecting
the fact of these being in either case tubes, the results of
my experience and investigations are opposed to this
view. It is evident to me from the Plate XV, fig. 14, in
the descriptive catalogue of the Royal College of Surgeons,
that if the tubes there represented are intended to show a
form of structure analogous to dentinal canals, as they are
generally termed, the author has made a great. mistake.
I may observe, that in the end of the crab’s claw, as seen
by the microscope, there are, as in other parts, the two dif-
ferent kinds of structure just described, one consisting of
alternate dark and light, generally sinuous, lines, extend-
ing from the superficial towards the deep surface of the
shell generally considered to be tubular. These lines
exist in every part of the shell sufficiently thick to present
them, and, in certain positions, as in the end of the claws,
their course gives them very much the appearance of den-
time. However, I may repeat the observation, that, in
the claw, especially of the very young animal, they de

generate into mere dots before they arrive at the cavity of
the claw, and present nothing in their appearance of a
tubular character. The cause of this arrangement of the
particles of the shell has been explained, and there can
be little doubt but that this same explanation applies to

88 FORMATION OF SHELLS OF ANIMALS, ETC.,

the spaces existing between the longitudinal portions of
dentine. These latter spaces are in principle analogous
to the canaliculi of bone, which will be fully explained in
the article on bone. Hence, in one form of bone, the
cementum or crusta petrosa canaliculi and dentinal canals
sometimes exist together. The dentinal canals are merely
spaces of feeble or imperfect cohesion, continued from the
interglobular spaces, where such exist, between longi-
tudinal portions of coalesced dentine to the pulp-cavity.
These passages, becoming a little widened from the con-
traction of the part in drying, and containing air, seem
to have, under the microscope, especially if appearances
depending upon distance are not sufficiently allowed for,
the appearance of tubes. It is, however, incompatible
with the function of tubes, as they exist mm other parts,
that a system of such organs, intended for the conveyance
of secreted fluids, should be simple prolongations of the
interstices of the body, as are the spaces between globular
portions of dentine and the pulp-cavity of a tooth, this
latter, notwithstanding its size, being only a cellular
‘interval. The other structure is distinctly tubular. It does
not exist, excepting in the tegumentary part of the shell, and
it is this which is most unquestionably represented in the
plate before referred to. These tubes pass from the external
surface of the shell, through its substance, to its deep one.
They have distinct parietes; and their peripheral extre-
mities in different parts of the same shell present very
different forms. All along the convex border of the claw
each of these tubes projects beyond the surface, where it
becomes free, presenting generally a feathery extremity,
or sometimes it seems split up into small fibres like a
brush. (See fig. 5 a, a.) Just at the point, and all
along the biting edge, these tubes are rather smaller and

ee

oor

BY MOLECULAR COALESCENCE. 89

more numerous; but, as might have been expected, they
have not the feathery appendage. Notwithstanding, their
ends are free and prominent. In the tubes represented in
the plate alluded to no projecting ends are shown, these
having been most probably ground off in making the pre-
paration, but, in other respects, they perfectly agree with
those I am describing, but in no respects with the flexuous
Imes before described. I have thin sections of crab’s
claw which had not been boiled, showing these tubes, but
they are troublesome to make. They can be most easily
shown in the very young crab, but the best way to see
them is in the decalcified shell. Now, I can easily ima-
gine that tubes thus constructed, with one of their ex-
tremities expanded, and thus rendered favorable for the
operation of extensive endosmose or exosmose, and with
the other extremity close to the part of the shell where
the globular carbonate of lime is chiefly found, would
serve admirably to convey the water in contact with the
surface of the animal, containing salts of lime, to the
membrane lining the shell, where a quantity of sub-
carbonate of soda is always present—(this circumstance
will be treated of more fully hereafter)—and thus to bring
into operation all the conditions required to form the
globular carbonate which occurs in this situation. But,
on the contrary, in the ivory of the tooth, circumstanced
altogether different to the claw of the crab, such tubes
could be of no use, especially as they would be covered
with a layer of enamel, and in some animals with a layer
also of cementum. Now, as it is extremely probable that,
with organs so decidedly tubular, there would not exist
another set of tubes to perform the same function. An
additional reason is here afforded in favour of the opinion
of the structure of these alternating dark and light lines,

90 FORMATION OF SHELLS OF ANIMALS, ETC.,

being as before described. It may be observed, further,
that interstices of precisely the same character as those ex-
isting between the particles of dentine are found also be-
tween the analogous portions of enamel, which are also
considered by some anatomists as distinct tubes. The
part of the shell of this class of animals next requring
notice is that which is situated between the muscles, giving
attachment by each of their surfaces to muscular fibres,
and therefore, both in situation and function, being ana-
logous to bone. I allude to the parts called by anatomists
“‘apodemata.” These parts are made up of layers of cal-
cified membrane rather loosely connected together, having
the appearance when dried of pieces of white paper stuck
together. The membranous layers of these parts, when
just beginning to calcify, exhibit all the stages of calcifi-
cation very distinctly. In no part are the facts showing
molecular coalescence better seen, from the minutest par-
ticles up to perfect globules, with lamine and radiating lines,
and, if the part be sufficiently thick, the coalescence of these
globules to form layers made up of the horizontal undulating
lines, called lines of growth, and the perpendicular sinuous
lines, or the so-called tubules of physiologists can be well
seen. These parts require no other preparation than
that of drying the shell, and then splitting off the thinnest
possible pieces, which may be examined either in glycerine
or turpentine. It is scarcely necessary to state, that these
parts, in all shells, are not equally favorable for exhibit-
ing these appearances ; several, therefore, ought, if neces-
sary, to be examined for that purpose. Of course the
regular tubes, mentioned as existing in the tegumentary
part of the shell, passing from its deep to its superficial
surface, are absent in these parts; but, m other respects,
their structure is similar. The last part of the shells of

BY MOLECULAR COALESCENCE. . 9]
crustaceans to be mentioned is that which corresponds to
the osseous tendons of birds. It is to be found most deve-
loped where it is attached to the claws called the nippers.
There is one attached to all the extreme claws. This part,
like the preceding, is buried between muscular fibres.
It consists of fibrous layers partially calcified, applied, toge-
ther. Its structure is like that of the last part. Thin
transverse sections through the thickest part exhibit the
lines and lamelle, as described in the tegumentary portion.
Frequent reference having been made to the resemblance
between the form of the carbonate of lime in these shells
and that in the artificial products, I would wish it to be
particularly observed, that in comparing these products—
the artificial with the natural—the parts compared must be
in the same molecular condition, that is, the molecular,
the globular, and the laminated of the one, must, be
severally compared with the corresponding forms of the
other, as there is but little resemblance in the appearance
of the different forms of this compound, whether artificial
or natural, when in different states of molecular arrange-
ment; but the natural products do not differ in this re-
spect more from the artificial than the various forms of
the latter, in their dissimilar molecular conditions, differ
among themselves; for nothing can be more unlike in
appearance than the clear spherules, as they exist sepa-
rately, and the globular bodies which they form by their
coalescence, when their molecules have undergone their
final arrangement into lamin and radiating imperfectly
erystalline fibres, the closest inspection of the one could
never suggest the idea of their being made up of the other.
Such being the resemblance of the various parts of the
shell in this class of animals, with the corresponding forms
obtained by the artificial process, it now remains to ex-

92 FORMATION OF SHELLS OF ANIMALS, ETC.,

amine the chemical conditions under which the natural
products are formed, and to compare them with those of
the artificial process. It will be remembered that, for the
production of the artificial calculi, two separate solutions
are necessary, one containing subcarbonate of potash or
soda with a glutinous material, the other a salt of lime,
and that these solutions are to be gradually mixed with
each other. Now, as it will be easy to show that these
conditions exist as perfectly in the shells of crustaceans as
they were described to exist in the artificial process, ex-
actly the same results may naturally be expected in both
cases. In the first place, I may observe, that an alkaline
solution containing subcarbonate of soda and albumen,
can easily be demonstrated on that surface of these animals
which is covered with a calcareous shell. In the fluid
taken from this part in the crab or lobster albumen is
thrown down by boiling, and subcarbonate of soda can be
detected by the proper tests, and where the quantity of
this fluid is insufficient to admit of the application of the
ordinary reactives, the surface in contact with the shell
can always be shown to be alkaline by simply holding a
piece of reddened litmus paper for a short time in contact
with it. I may observe, also, that this fact applies equally
to molluses and other animals which I have examined,
whose surface is covered with a shell of carbonate of lime.
The production of an alkaline carbonate in these instances
may then be looked upon as the effect of a natural pro-
cess, and results, without doubt, from the decomposition
of some of the salts of potash or soda contained in the
medium in which these animals live, or with which their
surface is frequently brought into contact. Under what
agency this decomposition is immediately effected is not
apparent, but it will probably be classed with vital pheno-

BY MOLECULAR COALESCENCE. 93

mena, until a more advanced state of physiological and
physical science reveals the chemical, or more probably
the galvanic, apparatus by which it is produced. But at
present the fact is all that is necessary to be considered in
this mvestigation. And in the second place, that as these
animals live very much in a fluid containing various salts
of lime in solution, and as their shells are in all parts
porous, and in some traversed by passages extending from
the deep to the superficial surface, it seems impossible,
under such physical and chemical conditions, that these
two solutions, one containing salts of lime, the other alka-
line, carbonate, and animal matter, should not first pene-
trate, agreeably to the law of endosmose, the tissue of the
shell, and then diffuse themselves, in consequence of their
unequal densities, through its substance, and lastly, meet-
ing together, undergo the same chemical decompositions
with the same results as in the artificial process. If,
under such physical and chemical conditions, these effects
are not produced, then laws, which under similar circum-
stances are invariably operative, must here be suspended.
But in the present instance exactly the same form of car-
bonate of lime is produced as ,by the artificial process,
which is the best evidence possible in favour of the pro-
cess in the two cases being also the same. Now, with
this fact, and considering that the same conditions, both
physical and chemical, have been shown to exist in the
shell-process as in the artificial one, the evidence in favour
of the identity of the two processes—the natural and arti-
ficial—is conclusive. But, notwithstanding all that has been
said, it is possible that this explanation may be objected to
by some as being too mechanical to be true. The cell-
germ hypothesis requiring that all this should be regarded
as the operation of the vital principle; that the globular

94 FORMATION OF SHELLS OF ANIMALS, ETC,

portions of carbonate of lime of different sizes should be
looked upon as cell-nuclei and “cells having an organic
basis essentially cellular, within the cells of which imor-
ganic matter is secreted and deposited ;” that their curvi-
linear contour should be regarded as the effect of a vital
force, and the coalescence of two globules into one as evi-
dence of cell multiplication by division. Now, in meeting
this objection, I may observe, that if the globular portions
of carbonate of lime occurring in these shells, so much
like the artificial globules as to be deficient in no point
denoting identity of structure, are the effect of a vital
force, I see no reason for questioning the identity of the
vital and physical forces, since, in this case at least, their
effects upon matter appear in all respects the same.
Furthermore, as it has been shown that these shells are
porous and partly membranous, and that the globules of
carbonate exist in various parts of their substance, and
that there is also an alkaline solution in contact with the
deep surface of the shell—indeed, that there exist, either
within its tissue or contiguous to it, all the conditions ne-
cessary for endosmose, diffusion, and chemical decompo-
sition, it must follow, as a natural consequence, that, if
these globules are not formed on physical principles, but
by the vital force, the first act of this force will be to put
a check upon all these physical agencies. To prevent
chemical action, the external surface of the shell must not
be penetrated by the water containing one of the elements
of the globular carbonate of lime, nor the internal or deep
surface by the fluid furnished by the animal containing its
other elements, notwithstanding the existence of tubes ex-
tending from the one surface to the other has been demon-
strated. And if these solutions should come into contaet—
and with such mechanical contrivances, apparently in

BY MOLECULAR COALESCENCE, 95

tended for the very purpose, it seems to be unavoidable—
then vitality must prevent them from acting chemically
on each other; the vperation of their chemical affinities
must be overruled, and rendered inoperative. And why
ali this opposition? Simply that vitality may be afforded
an opportunity of doing that which it has been demon-
strated can be just as well done without its aid or inter-
ference! As this is the only conclusion which such a
supposition leads to, there is, I think, overwhelming evi-
dence that the formation of the globules of carbonate of
lime—the organic-cells of some authors—in the shells of
crustaceans is due directly to physical and chemical
agency, and that these globules are identical in structure
and in their mode of formation with the artificial globules.
But, lest it should be inferred from all that has been
stated that I regard the formation of the shells of crusta-
ceans as entirely physical, a few words of explanation, as
to the limit which may be assigned to the operation of
this agency in the formation of these structures, are neces-
sary. Without pretending to draw an exact line of de-
marcation between what is physical and what physiologi-
cal, I may observe that there is just one fact deserving
notice which goes a great way towards effecting this,
which is, that when vitality makes use of material sub-
stances it never disunites them from those influences
which are at all times acting upon them, but, on the con-
trary, it employs these influences, making them subserve
its own purposes, whether the matter employed be in the
simple condition of a crystal or the complex form of a
vegetable or an animal structure. Hence, in the formation
of the shells of crustaceans, vitality devises the means by
which the materials composing them are brought together,
adjusts their proportions, and regulates the conditions

96 FORMATION OF SHELLS OF ANIMALS, ETC.,

under which they are acted upon by the physical forces
during the different stages of their elaboration into per-
fectly formed shells; just as, in the artificial process,
vitality displayed in an act of the will first brings together
the material substances necessary to form the globules of
carbonate of lime, then proportions them, and, lastly,
arranges the conditions under which these materials are
required to be acted upon by the physical forces. There
is, however, probably this difference, that the latter is the
result of distinct and separate mental acts, whilst the
former is all comprised in one act, which embraces also
all the operations of nature.

The preceding observations, in reference to the chemical
conditions under which the globules of carbonate of lime
are formed, apply entirely to the dermic portion of the
shells of crustaceans, and especially to those parts where
the globules are formed entirely out of the reach of the
blood, as close to their external surface, or around the
passages extending from this surface to the pigment
membrane. But there are other parts of these shells, as
the septa (apodemata) between the cavities contaming the
muscles and those parts of the shell corresponding to the
osseous tendons of birds, where these conditions cannot be
demonstrated. - In these situations, the shell bemg im-
bedded in the substance of the muscles, and giving attach-
ment to their fibres, corresponds im function more to the
endo-skeleton or bone than to the exo-skeleton. Now in
these parts of the shell the globules of carbonate of lime
are formed exactly as in the other parts, and as in the
artificial process. Nowhere can all the stages of molecular
coalescence, from the minutest particles up to the most
perfectly formed globules, be better seen than in these
septa; a fact indicating an undoubted identity of process

BY MOLECULAR COALESCENCE. 97

and similarity of physical and chemical conditions. With
respect to the alkaline carbonate, it can be demonstrated
on the surface of the parts connected with these septa ;
hence this chemical condition is the same as in the other
parts of the shell, so that the difficulty exists only with
regard to the source from which the salt of lime proceeds,
and the route by which it arrives at the surface of the shell,
moistened by the subcarbonate of soda. But this question
admits at once of simplification and the removal of the
first part of the difficulty, there being but one source by
which the salt of lime can be furnished, which is the water
taken into the system of the animal through the imstru-
mentality of its digestive apparatus. Now, as to theroute,
this can only be the vascular system, which, being that
through whose medium the elementary constituents of all
the other structures are conveyed to their various points
of destination, may be considered also to convey the soluble
salts of hme to the parts where they are required. Now, it
ean be shown, by the application of chemical tests to these
septa, that an alkaline carbonate is formed on their surface,
and, by the microscope, that minute as well as larger
globules of carbonate of lime exist in the same situation ;
and, therefore, it may be fairly concluded that this carbonate
of lime is formed in the place where it is found, and not in
the interior of the adjacent blood-vessels, and, more
especially, as bemg insoluble it would not pass through
their coats in particles of such a size. Hence, taking all
these circumstances into consideration, it seems in the
highest degree probable that all the conditions, both
mechanical and chemical, necessary for the formation of
carbonate of lime in the case of the deeply-seated shell-
structure, are essentially the same as in the superficial ones.
The fluid contaiing these substances in different states of
a

98 FORMATION OF SHELLS OF ANIMALS, ETC.,

combination is the blastema or nutritive fluid of physio-
logists advocating the cell-germ theory; and, containing
all the elements of the structures in progress of formation,
it may be considered also as the nutritive fluid, according
to the view now advocated. There is, however, this
difference in the explanation of the process by which this
fluid is elaborated. According to one view the vital prin-
ciple is imparted to separate portions of matter, endowing
them with distinct and individual powers, to be employed
in accordance with certain hypothetical laws ; according to
the other, vitality is considered to disdain all such sub-
division of a general principle and such co-operations, yet
still to produce the same effects on this fluid but by the
employment of certain physical forces from whose operation
matter cannot be dissociated. I shall next consider the
structure and mode of formation of shell-tissue as it occurs
in the shells of molluscs. Of these I shall select such as
are the most common, and in which the facts observed
connected with their structure and development admit of
bemg most easily verified. The shell of the mussel, and
still more that of the oyster, furnishing all that is necessary
to be observed in this class of shell-tissues, I shall confine
my observations to them, taking it for granted that all the
rest of this class of animals have their shells formed upon
the same plan. The shells of the mussel and oyster are
laminated like that of the crab or lobster, and grow in the
same manner by the successive additions of new layers to
the internal surface of the layer last formed; so that each
valve of a shell presents the form of a cone, whose summit
is the valve or layer first formed, and whose base is the
layer formed last,—the layer in immediate contact with
the surface of the mollusc. Each layer also consists of a
membrane calcified, especially on its external surface

BY MOLECULAR COALESCENCE. 99

This arrangement is best demonstrated by putting the
entire valve of a small mussel into hydrochloric acid, so
feeble that the too sudden escape of the carbonic acid will
not break the membrane into fragments, but raise it entire.

Fig. 6.

The most external membrane of the shell of this mollusc
does not become calcified, nor does it receive an addition
to its entire surface, but only grows at its free border. It
is of a horny structure, presenting distinct markings. But

100 FORMATION OF SHELLS OF ANIMALS, ETC.,

the internal membrane, on the contrary, as the mussel
grows, receives an addition of new membrane to the whole
of its inner surface. This membrane is perfectly homo-
geneous, having no markings whatever, excepting close to
the edge of the valve, where it is continuous with the
external horny membrane. Nearly the same arrangement
exists in the lamine of the shell of the oyster, which being
much less firmly connected together, are more favorably
circumstanced for the examination of the process of calci-
fication. The physical conditions favorable to the process
of coalescence of the minute particles of carbonate of lime
into a globular form are less interfered with by so close a
proximity of its membranous and calcified layers as exists
in the shell of the mussel. Hence I shall confine my
descriptions almost entirely to the appearances showing
the nature of this process, as they are found in the shell of
the oyster. I may observe that I have found those oysters
which are of the largest size, and which have large cavities
between their lamine, as represented in fig. 6 a, to be best
adapted for displaying the development of shell-tissue, and
that the most successful examination I have made of this
tissue in its earliest state of calcification have been in the
month of June. I name this circumstance since the season
of the year may have a great deal to do with the develop-
ment of the shells of these molluscs. The common way
of displaying the structure of these shells is by making
vertical sections of various parts of them, and grinding
them sufficiently thin to allow of being viewed by trans-
mitted hght. ‘These sections are very useful, and indis-
pensably necessary to show certain facts connected with
shell-structures ; but they afford no information relative
to their development. This can only be learned from the
examination of extremely thin, partially calcified lamine,

BY MOLECULAR COALESCENCE. 101

sufficiently transparent to admit of being seen by trans-
mitted light, without the necessity of any kind of manipu-
lation which can at all injure their structure, or alter
their natural appearance. The earlier the stage of calci-
fication, the more complete and spherical will be the forms
of the carbonate of lime, and the more satisfactory the
indications of molecular coalescence. If the piece of
membrane examined has its surface entirely covered with
caleareous matter, it will not show the earliest stages of
coalescence, and therefore will only furnish imperfect
evidence of this fact. The mdications of this process are
best displayed on those portions of calcifymg membrane
which are situated over the mterlaminar cavities before
alluded to, separating these spaces from the general cavity
or hollow of the valve. In such situations the coalescing
particles being placed on a membrane intervening between
two spaces will be almost as little mterfered with in their
process of coalescence by the pressure of the adjacent
parts, as if they were on the slide of glass, as in the arti-
ficial process ; and hence the globular particles formed on
membranes so situated, ought to be as perfect as those
produced by that process. And such is the case. I have
in my possession specimens of these globules in every
stage of coalescence, distinguishable from the artificial
formation only by the membranous tissue which forms
_ their bed. Partially calcified membrane, like the above,
is most easily obtained by keeping oysters which have
those caverns on their shells from the contact of water,
until the branchize become dry, when the calcifying mem-
brane, becoming slightly discoloured and hardened, can
be both more easily distinguished and more readily sepa-
rated from the contiguous parts of the shell. (These
globules are not to be confounded with crystals which

102 FORMATION OF SHELLS OF ANIMALS, ETC.,

form at the same time.) Such specimens can either be
put up in glycerine or in Canada balsam. And it is
scarcely necessary to add, that they are only to be met
with occasionally, and under favorable circumstances,
when the development of these parts of the shell is just
in the proper stage. The parts of these shells, on which
the globular carbonate of lime occurs (though in an in-
ferior degree of perfectness of form and transparency to
those just described), to be next examined, are the septa,
situated between the interlaminar cavities. These cavities
are always filled with saltish water containing soluble
animal matter, and free carbonate of soda, so that red-
dened litmus paper put into this water soon becomes blue.
The globular deposit is always on the surface of the lamina
in contact with the fluid, and therefore the lime has most
probably been furnished by this fluid, after the alkaline
carbonate, still in excess, had decomposed the lime-salt
held by this fluid in a state of solution. Hence there is
in this case very strong evidence that the lime entermg
into the composition of the globular carbonate comes
directly from the water in which the animal lives. The
only objections to this conclusion which can be raised,
are, that the water in these spaces never was contaminated
with a salt of lime, or, if it had been, this salt was sepa-
rated from it before the solution could get access to the
cavity. Now, as all common water contains lime in solu-
tion, in one or other state of combination, the first objec-
tion can have no weight; as to the second objection, it
may be observed, that the water contained in these spaces
has lost a substance which it had before held in solution,
but that it now contains an excess of the very compound
which always precipitates this substance, a sufficient reason
for its absence. But, besides, there is animal matter in

BY MOLECULAR COALESCENCE. 103

this solution, and the other conditions necessary to form
a globular compound of the absent substance. And this
compound, too, actually exists on the side of the cavities
containing the fluid in which these chemical changes are
taking place, showing that this compound is not only
furnished in part directly from the water, but also that
the principle of its formation is analogous to that of the
artificial process for obtaiming the same form of carbon-
ate of hme. Hence, weighing all these circumstances and
deductions together, it will appear next to certain that
both inferences are correct, and that tlrerefore the fluid
contained in these spaces cannot have been deprived of its
salt of lime before it arrives there. The thinnest septa
between these cavities consist of several layers of an ex-
quisitely fine-and perfectly homogeneous membrane, coated
more or less thickly with calcareous matter. If the layer
bound immediately the cavity, the surface of it in contact
with the fluid is, as was before observed, studded with
particles of carbonate of a globular form; if the layer is
not so situated, but connected with another layer, the
calcareous matter is in thin scales, which can be demon-
strated to result from the flattening out of the globules.
This membrane can always be shown by examining a
fragment of one of these septa with the microscope, while
it is acted upon by very diluted hydrochloric acid; but
very frequently it can be found only partially or very
slightly covered with coalescing particles of carbonate of
lime. And this is the most favorable condition under
which it can be examined. Dr. Carpenter says, that he
has ascertained that the nacreous lustre is due to the pli-
cation, or folding of a single layer of this membrane in
such a mode that the folds shall le over one another in
an imbricated manner. Although Dr. Carpenter’s evi-

104 FORMATION OF SHELLS OF ANIMALS, ETC.,

dence upon this point appears very clear and circum-
stantial, it does not agree at all with the facts which
occurred to me in examining the same parts, and there-
fore I am obliged to differ from him. I have never seen
in this membrane, when completely separated from the
calcareous matter, any trace of this nacreous lustre, and
consequently believe it to be due entirely to the carbonate
of lime, and not to the membrane on which it is deposited.
In my experiments I have always employed the polariscope,
which furnishes the best means of deciding this pomt. More-
over, the nacreous lustre of a piece of shell is not in the
least impaired by boiling it for any Jength of time in hquor
potasse ; and but little so by heating it to redness, which
must have been the case if the lustre were produced by
the delicate folds of what Dr. Carpenter has called the
nacre-membrane. Now, from what has been stated con-
cerning the chemical part of the process by which the
carbonate of lime in a globular form is produced in the
shells of crustaceans, but little remains to be added to
what has been already noticed of the formation of this com-
pound on the septa between the interlaminar cavities. A
few words will finish this part of the subject. In animals
of this class, all that surface which comes in contact with
the shell is moistened with a solution of carbonate of soda
and animal matter, which can be easily demonstrated, as
before observed, by the proper tests. I may just notice,
however, that a piece of reddened litmus paper, kept in
contact with the surface of a mussel or oyster for a minute
or two, never fails to show the presence of an alkali. I
cannot say that this is the case only with the part con-
nected with the shell, as I have not tried it on ail parts of
these animals; but that does not at all affect this question.
Besides this secretion of alkali, a membrane is formed on

BY MOLECULAR COALESCENCE. 105

the surface of the oyster, to receive the carbonate of lime
precipitated from the water, which has free access to the
surface of this membrane next the shell. In consequence
of this membrane, with the calcareous matter formed upon
it, beginning to adhere, first to the middle part of the
previously formed layer of shell, and last to the circum-
ferential parts, the water in which the oyster is placed
can easily pass under those parts of this layer which are
being calcified. And also in this way the water is gra-
dually shut out from the parts of this layer as their calcifi-
cation becomes completed. As the form of the growing
oyster becomes less convex, its surface does not keep
parallel with that of the shell; hence, the membrane
formed on this surface bridges over the most concave part
of the shell, and a space is left, at first between the shell
and this membrane, but afterwards, when the membrane
is calcified, this space is of course between the last two
layers of shell. It is thus that these interlaminar cavities
are formed. ‘These are the portions of membrane, which,
when only partially calcified, have been already noticed as
displaying the most perfect forms of the globular car-
bonate of lime. (See fig. 6,'4, which is a representa-
tion of the shell of one of the largest kinds of oysters ;
a, a, marking interlaminar spaces in which the alkaline
fluid was contained; 6, 6, similarly formed spaces, but
without fluid, and filled up with amorphous carbonate of
lime ; ¢c, c, septa between the spaces containing the fluid
before mentioned. B is a representation of portions of
calcifying membrane, taken from the part where this
membrane bridges over the deepest parts of the shell, as
represented by c¢, fig. A; a, a, marking the molecular
state ; b, b, single spherules and dumb-bell-shaped particles ;
c, laminated globules, in which the cross can be seen by

106 FORMATION OF SHELLS OF ANIMALS, ETC.,

polarized light.) I may observe, that, although the
primary and secondary forms assumed by the globular
carbonate of lime are perfectly alike in crustaceans and
molluscs, yet their ultimate forms are very different ; but,
these differences depend upon mechanical causes, and
admit of being imitated to a great extent by modifying
the artificial process. In crustaceans, the ultimate form
of the carbonate of lime is the same as that of those
artificial caleuli which are formed on the under surface of
the glass slide, and which have the laminated structure
with the radiating lines. These, during their formation,
have not been so much exposed to pressure from the con-
tact of the surrounding parts. In the shells of molluscs, as
the oyster, the ultimate form is that of flattened plates,
closely connected together, and overlapping one another.
This form can in some measure be produced in the artificial
process, by allowing the globular deposit to remain at the
bottom of the vessel in which it was formed, for several
months. To produce this effect, the carbonate must not
be mixed with triple phosphate. The white gum is the
best in this case, and the quantity of alkali must not be
sufficient to saturate the thick solution of gum. In good
natural specimens of this form, globules perfectly spherical
and beautifully laminated can be seen mixed with those
in which the process of flattening is gomg on, and can be
distinguished in its several stages. This is especially
indicated by the laminated form becoming less and less
distinct from the circumference to the centre, where
it remains visible longest, afterwards disappearing alto-
gether; and the form having become flat, that which was
a globule then becomes reduced to a very thin plate, with
an irregular or zigzag margin. During this transforma-
tion of the globules into plates, and after these plates

BY MOLECULAR COALESCENCE. 107

have acquired their ultimate form, they show no tendency
to coalesce, but remain intimately connected with the
membrane on which they were formed. I have several
specimens showing all the appearances above described.
There is a form of carbonate of lime occuring chiefly at
the edge of the valves of these shells, which has been
particularly noticed by Dr. Carpenter, in the Pinna. It
also occurs in pearls produced by the oyster, making up
the principal part of their substance, where, as in other
parts, 1t can be shown by a proper mode of examination to
result from the coalescence of other smaller particles into
globular bodies of various sizes, which occupying the
softer parts of the shell, do not become pressed into flat
plates, as in the densest parts, but which are still so
crowded together, as to be prevented from retaining the
spherical figure. Besides these forms of carbonate of lime
in the shell of the oyster, there is yet another form which
is neither globular nor distinctly crystalline. It is the
amorphous carbonate before alluded to, as occupying some
of the interlaminar spaces in the place of the alkaline
fluid which is contained in the other spaces. This amorphous
carbonate can only result from the mixture of successive
portions of water, contaiming in solution the compounds
of lime, with the solution of alkaline carbonate formed on
the surface of the animal. These two fluids finding
access to these cavities, and the latter bemg probably
deficient in animal matter, a decomposition takes place,
and a carbonate is formed, not of the globular but of the
amorphous character. Occasionally, in the thin plates of
oyster-shell, branching dark lines are seen, resembling, in
their mode of ramification, Conferve. These, in the
perfectly calcified shell, are so blended with the contiguous
calcareous plates, as not in such cases to admit of being

108 FORMATION OF SHELLS OF ANIMALS, ETC.,

satisfactorily examined. However, in an imperfectly
calcified layer, sufficiently recent, they can be so far
detached, whilst in their growing condition, from the
layers of shell, as to remove all doubt as to the fact of
their being true Conferve. These growths are found on
the surface of the calcifying membrane, which is exposed
to the contact of the salt water, this being without doubt
the medium by which they are brought, in the condition
of sporules, into this position. The quantity of this
confervoid growth differs very much in different shells.
In shell-structures the earthy matter is considered by
those who have written upon the subject, to be contained
in the interior of cells. Dr. Carpenter, when treating of
the prismatic cellular substance of shells, observes, that
“The resemblance in their structure and position between
the prismatic cellular substance of shells, and the prismatic
epithelium covering the mucous membrane of higher
animals, leaves no room for doubt of their analogy, and
we may consider this form of shell-structure in the light
of a calcified epithelium, the carbonate of lime being
deposited in the cavities of the cells, and in general
completely filling them. In most sections of Pinna a
greater or less number of dark cells may be seen, which
are usually disposed with some degree of regularity.
These I have reason to believe to be cells mcompletely
filled with carbonate of lime, the spaces remaining in
which, being occupied by air only, present a dark ap-
pearance under the microscope, according to the general
principle well known to observers.” Now, according to
this view of the structure of shells, which is I believe the
one generally maintained, cells are formed first, and
afterwards carbonate of lime is deposited in their cavities ;
hence, in the process of development of shell-tissue,

BY MOLECULAR COALESCENCE. 109

these pre-existing cells’ ought to be visible under the
microscope; and the carbonate of lime afterwards de-
posited in their cavities ought to be apparent when
examined by the polariscope, especially as the deposition
must be somewhat gradual, and the means of detecting
it by this imstrument are most delicate and certain.
However, notwithstanding these facilities, and having the
aid of all that is necessary for microscopic examination,
I have not been able to see anything which gives the least
countenance to such a view, or which, in any way, agrees
with the appearances said to present themselves in this
class of tissues. In the first place, the membrane on which
the carbonate of lime is precipitated is in most cases as
devoid of marking of any kind, and as transparent, as a
film of glass. This is especially the case in the oyster-
shell, and many parts of the membranous layers of the
erab-shell, where it forms septa between the cavities con-
taining the muscles, so that thismembrane, in these cases,
cannot be regarded as consisting of cells for the secretion
and retention of the earthy matter. ‘Secondly, when this
membrane is beginning to be ealcified, and only very
partially covered with minute particles of earthy matter,
nothing can be detected, either upon, or within it, so re-
lated to these particles, as to answer in any way to the
description of a cell with these particles: contained in its
cavity. All that can be seen are minute particles joining
together to form larger ones, and, these again joining to
form particles still larger, until they acquire the size and
form of distinct globules; but still, during the whole of
this process, nothing like a membranous cell ever makes
its appearance. It is true, that if these particles of
earthy matter are acted upon by hydrochloric acid, an
animal basis is left, the same as if a similar compound

110 FORMATION OF SHELLS OF ANIMALS, ETC.,

formed artificially were treated in like manner; but this
basis being a constituent of the smallest as well as of the
largest particles, and being formed simultaneously, and in
combination with the carbonate of lime, must be so blended
with the earthy matter of the latter, as to be present in
every part of their substance; hence the two materials—
the earthy matter and the animal basis—being thus incor-
porated in every globule large enough to be looked upon
as a true cell, would in no way agree with the idea of a
hollow body with a membranous exterior, and with an
internal cavity either completely or incompletely filled
with carbonate of lime, which, from the descriptions given
of these cells in the works of those who have written upon
the shell-tissues, is evidently the idea generally enter-
tained of these globular bodies. And what is still more
remarkable, these so-called cells are believed to possess
an inherent vital power of forming others exactly like them.
And, thirdly, when the carbonate of lime is precipitated
on a membrane which is not homogeneous, but is marked
out into squares or parallelograms or other figures, still
the marking has no influence on the earthy matter formed
upon its surface. Sometimes, however, it seems to follow
these markings, and then has the appearance of being
contained in cells ; yet such a circumstance is completely
accidental, as any one may convince himself who will
examine such appearances without any bias; when it will,
at once, be apparent, that the earthy matter is deposited,
and extends itself irregularly, and without any limitation,
by such markings, or without in the least corresponding
to them. I may just notice here, that although the curvili-
near contour may not be regarded by histologists as essential
to organic cells, yet, that the tendency of the vital force is
always to produce that form. Hence in the descriptive and

a i

BY MOLECULAR COALESCENCE. 1a va

illustrated catalogue of the histological series contained in
the Museum of the Royal College of Surgeons, Plate XVI,
fig. 14, there is a representation of perfect rhombohedral
masses resembling crystals, taken from the shell of the
common oyster. Such crystals are found, when treated with
muriatic acid, to leave a residue of the same form as the
original crystals, from which circumstance alone they are
considered to be organic products, the residuum being
regarded as the cell, and the earthy matter the cell-con-
tents. The crystalline form, in these cases, is attributed
to “the animal cell not having sufficiently controlled the
mode of deposition of the earthy particles, they have, in
consequence, assumed the crystalline form.” I may ob-
serve, that, in globular calculi, containing a large propor-
tion of triple phosphate, when im a state of molecular dis-
integration, in consequence of bemg kept in a denser
medium than that in which they were formed, almost the
same kind of crystals are produced. See article, ‘ Com-
plete Molecular Disintegration.’ The particular structure
named by Dr. Carpenter, “ prismatic cellular substance,”
found in some parts of the shell of the Pinna, and about
the edge of the shell of the oyster, forms no exception in
its mode of formation to that of the other parts of these
shells. But, on the contrary, if examined in a sufficiently
early stage of development, it will be seen to present ap-
pearances as indicative of molecular coalescence as any
other shell-tissue. This substance occurring in the softer
and more membranous shell-tissues, where the globular
particles are not exposed to pressure on all sides, as in the
hardest parts, and, therefore, flattened out into scales,
is only pressed laterally by the adjacent globules, and,
therefore, flattened only on the sides where they he in
contact, the parts of these globules which are free retain-

112 FORMATION OF SHELLS OF ANIMALS, ETC.,

ing their convexity. In Dr. Carpenter’s plate, represent-
ing a portion of the shell of Pinna, two small spaces,
situated at the conflux of several compressed globules, are
represented dark. In these the calcareous matter is said
to be deficient, and the dark appearance, as before ob-
served, is attributed to the presence of air. This appear-
ance is fairly represented in Dr. Carpenter’s delineation ;
but the cause he assigns for it is not, I am persuaded, the
right one, being unconnected altogether with air. It
is caused by the particles of globular carbonate of lime,
in which this appearance is observable, bemg both more
dense in structure, as well as smaller than those to which
they are contiguous, and consequently more highly re-
fractive ; hence the smaller, that is, the more convex these
particles are, the darker they appear. Ifa single layer of
these compressed globules be viewed by reflected lght
with the superficial or outer surface uppermost, the small
particles, looking the darkest by transmitted light, will

then appear to be of the densest white. The smallest, or

dark particles, are situated at the conflux of several larger
ones, and generally deeper, but not always. They present,
therefore, great difference in their shade and in their appear-
ance, accordingly as, when viewed, they are superficial
to or deeper than the contiguous particles. Now, these
particles being, from their greater density and smaller
size, more highly refractive than the contiguous ones, an
appearance is produced resembling that caused by the
presence of air; this appearance being imcreased by
the unequal refraction of the globules through which
these smaller ones are seen. But, it may be observed,
that, as the appearance of air in these particles is only ob-
servable when they are seen with one of their sides next
to the microscope, it cannot be occasioned by the presence

|

BY MOLECULAR COALESCENCE. 113

of air. These small globular portions are well seen in de-
calcified specimens. I have such specimens showing these
facts. I may observe, also, that the examination of the
decalcified shell of pinna perfectly agrees with the fact just
demonstrated, namely,that its component globules are made
up of earthy matter, and animal basis molecularly com-
bined, and not of cells formed first and afterwards filled
with the former material. In the shell perfectly deprived
of its component earthy constituent by hydrochloric acid,
the appearance is so little altered, that were it not for the
evidence afforded by the polariscope, the fact of its decalci-
fication might be doubted. The portions of animal residua
perfectly retaining their convexity, and their distinction of
dark and light parts, when viewed by transmitted hght,
show that something is left which had been in intimate
union with the carbonate; but, as a matter of course,
these appearances are less marked than before. There is
no appearance of distinct cell-walls in these globules,
when no pressure is made upon them; however, when
pressed together, their exterior denser layers, which owe
that density, as a natural consequence, to the mechanical
forces concerned in their formation, may be forced one
over another, and thus made to present the appearance of
a cluster of compressed cells. As for the presence of
nuclei, or the germs of cells in these residua, I
may have seen something as characteristic as the gra-
nules represented in p. xvi, figs. 2 and 10, of ‘The
College Catalogue, but I am not aware that I have ;
however, if I had seen such granules, or even some much
more defined and regular in their form, I should have
required evidence much more clear than has yet been
adduced, before I could be convinced that each of these
granules is endowed with the power of constructing a
8

114 FORMATION OF SHELLS OF ANIMALS, ETC.,

globule, anatomically and physiologically, like the one in
which it is contained. I have frequently seen pathologists,
in examining morbid products, point out cells with their
cell-germs extending through several generations ; but to
me the matter has always appeared to be entirely specula-
tive, and perfectly gratuitous. Lastly, if the exterior layer of
each of these globules had been a cell constructed according

to the cell-theory, for the purpose of secreting the carbonate _

of lime contained within it, the question might be asked
how it happens that, with the microscope, aided by the
polariscope, all the carbonate can be seen when perfect
globules are being acted upon byacid, gradually to disappear
from their interior, and to leave the part which it had
before occupied demonstrable, whilst, by the same means,
no deposition of carbonate into the interior of similar
bodies can ever be shown? whilst if it had been deposited
in previously formed cells, the fact of its deposition ought
to have been as demonstrable as that of its removal. The
only answer this question admits of is, that cells or
globules so constructed have only a hypothetical existence,
and that there are in fact no such globules apart from their
earthy constituent; but that in all stages of their develop-
ment, the earthy component and animal basis are always
found together, which being possessed of a property of
coalescence, as shown by experiment, pass through a
succession of coalescences, until they result in the forma-
tion of the globular bodies in question. The hard tissue
next to be considered is bone.

ON THE STRUCTURE AND FORMATION OF BONE.:

Of all the tissues which have been described in the
preceding pages, the calcified tendons in crustaceans come

y
-
j
4

BY MOLECULAR COALESCENCE. {15

nearest, in composition and function, to bone. These
tendons agree almost in every respect with the osseous
tendons of birds. Both structures give attachment to
muscular fibres, and are composed of the same chemical
substances, though in different proportions ; the carbonate
of lime preponderating in the former, the phosphate of
of lime in the latter. Now, considering that these struc-

tures present such marked points of resemblance, and

differ only in the relative quantities of one of their con-
stituents, it seems impossible, that they should be formed
upon totally different principles, and according to dia-
metrically opposite laws; that is, that the ultimate forms
assumed by the particles of the one should have been
determined by physical force, whilst the similar forms
assumed by the particles of the other should have been
determined by a vital force; hence, it must be inferred
that both are produced under the direct influence of the
same agency, whether it be physical or vital. Now I con-

' sider that the efficient cause determining the mode of

arrangement of the substances composing shell-tissues,
has been demonstrated to be physical ; and therefore, as a
quod sequitur, the mode of arrangement of the material
constituents of the osseous tissue must also be physical.
But as this is so important a question, and as this inference
is at variance with the opinion of all physiologists, I can-
not do less than make this tissue a subject of special ex-
amination. It is a well-known fact, that in every form of
hard tissue where phosphate of lime is present, there is
also mixed with it some carbonate of lime. The necessity
of this combination, and the use of the carbonate of lime
will be apparent from the following facts. If pure phos-
phate of lime be formed and deposited, under precisely
the same conditions as those mentioned in the process for

116 FORMATION OF SHELLS OF ANIMALS, ETC.,

obtaining the globular form of the carbonate of lime, it
does not, like this compound, assume that form, or lose
its crystalline character, but its crystals congregate into
globular masses ; if, however, a small quantity of carbo-
nate of lime be formed together with it, then the phos-
phate of lime, combining with this carbonate, forms a
globular coalescing compound, like that of the globular
carbonate of lime. This compound is not quite so homo-
geneous as that of the unmixed globular carbonate, but
its optical and physical properties are very similar. This
combination can be produced by introducing into the same
bottle a small quantity of phosphate of soda, and muriate
of lime, dissolved in separate portions of white of egg,
and allowing them to mix gradually, when a phosphate
and carbonate of lime will be formed. The carbonic acid
is furnished by the alkaline carbonate contaimed in the
white of egg, which is quite sufficient to prevent the
crystalline arrangement of a considerable quantity of the
phosphate of lime. This effect of a small quantity of
carbonate of lime is also beautifully seen in the change
which it produces on the form of the crystals of triple
phosphate, forming with that substance the largest and
most perfect spherical calcul. (See page 36). Having
now determined by experiment this important fact, which, —
being connected with the chemical composition of bone,
stands at the head of this imquiry. I shall next give the
results of a careful examination of the appearances pre-
sented by bone in its very earliest stage of development,
as seen in the ossifyimg tendons of birds, and in some
parts of the lower animals. The structure of the osseous
tissue has been too exclusively studied by means of thin
sections. These are not only useful, but for some purposes
indispensable, still they give no idea whatever of the

BY MOLECULAR COALESCENCE. PEF

appearances first presented by the earthy deposit, or of
the arrangement and form it assumes in a short time after
its precipitation. The osseous tendons which I have found
to be well adapted for this examination, are those of the
dorsal muscles of any young bird. In the parts of
these tendons where the ossification is just beginning,
minute scattered particles can be seen taking somewhat
the course of the tendinous fibres. On the same
tendon, rather nearer to this muscle, these particles
being more numerous, lie close together, and extend in
patches, of no definite form or size, along with its fibres.
In some of these patches, when examined by transmitted
light, darkish, ill-defined spots can be seen, arising, I have
no doubt, from a deficiency of the earthy matter at these
parts, and the accumulation of it in the parts around. In
others, where the earthy matter is much less in quantity,
the particles can be seen to have arranged themselves in
circles, more or less complete. As there can be no ques-
tion but that the process of ossification in these tendons
is essentially the same as in other parts, and that it is
identical in all classes of animals, I shall contimue the
description of the appearances presented by the earthy
deposit, as I have seen them in the bones of the reptile,
the fish, and the human subject. There are two forms in
which the ordinary process of ossification may be studied ;
one, where the ossifying process is confined to isolated
portions of earthy deposit; another, where the bone in
process of development is connected with perfectly formed
bone. The former can be seen very well in the young
frog, or in a very young fish. (Fig. 7 is a representation
of the appearance presented by the particles of phosphate
of lime taken from a frog about one inch in length,
and with no other dissection of the part than was neces-

118 FORMATION OF SHELLS OF ANIMALS, ETC.,

sary to remove it from the animal. It is preserved in
glycerine. a, is a piece of cartilage with nodulat edpor-
tions of earthy matter evidently formed upon it by the
coalescence of previously existing particles of various sizes,
but inclining to a rounded figure; 4, these nodulated
portions still further coalescing to form osseous rings.
These rings are, in this subject, formed upon a cartilagi-
nous sternum, and have been exposed by merely stripping
off the skin. They have no definite relation to the car-
tilage-cells beneath, nor is there any appearance of the
phosphate being deposited in their interior, or confined to

Fig. 7.

+ \ uik| aces (
prides ME fale

lef Ak ANNO

| : iS Wai

AIA
i 0 UH Hh

the intercellular substance around them. These rings
neither correspond in number nor in form with the car-
tilage-cells. Their long axes may be coimcident or at
right angles. Indeed, there is nothing which agrees with
the notion that the development of the one is in any way
connected with that of the other. These osseous particles
simply coalesce upon it as they do upon tendon, or upon
membrane where no such cells have ever existed. Hence
the use of cartilage in this and similar situations, is with-
out doubt simply to serve as a temporary substitute for

BY MOLECULAR COALESCENCE. 119

bone; and all those changes of structure Which have been
so elaborately described in the parts of cartilage, near to
which the process of ossification is going on, are only such
as are consequent on the removal of cartilage, and not
necessary for the production of bone, as is shown by the
fact that bone is formed just as well without cartilage as
with it. As the process of ossification advances, the
circular areas enclosed by the osseous rings become gradu-
ally but only partially filled up. (Fig. 8 is an accurate
representation of this stage of

the ossifymg process from the Hig: Be

same animal. ‘The part here re- Sud
presented had not been in any Tey es
way mutilated. It was in glyce- Sy z

S
rine. It shows- how the canali- Me S
culi are merely the result of A oe
spaces left between the coalescing wil
granules, which converge towards,
and terminate in, a central un-
ossified part, called a lacuna, or what physiologists and
histologists consider to bea “ bone-cell.”) The other form
of the ossifying process, that in which the bone in progress
of development is connected with fully formed bone,
resembles the one just described, in all pomts but one,
which consists in the osseous granules being deposited in
loops or arches, with their extremities connected with the
most recently formed bone. The spaces enclosed by these
osseous arches are at first large, but they become gradu-
ally but imperfectly filled up, exactly in the same manner
as the circular areas in the other form, and canaliculi and
lacune remain. ‘This form can be seen, also, without
mutilating the parts, in the young frog, as well as in the
tendon of the bird, as before observed. I have seen it

120 FORMATION OF SHELLS OF ANIMALS, ETC.,

very beautifully in the lamina spiralis of a child, aged
six years. In this case, the particles of phosphate of lime
are minute, but spherical, and show decided indications of
coalescence. I have in my possession a preparation show-
ing this fact very distinctly. It is scarcely necessary to
say that I have not mistaken the arches formed by the
cochlear nerves for bone. But the best of all subjects for
demonstrating the fact of molecular coalescence, is the
very young fish, in which occasionally the globular par-
ticles, containing probably a larger proportion of carbonate
of lime mixed with the phosphate than is contained in the
bones of other classes of animals, exhibit, under polarized
light, a dark cross, like the artificial globular particles,
and like many of those found in shells. Now, I may
observe, that in all these examinations of the imcipient
stage of ossification, as seen in the tendon of the bird,
in membrane, and in cartilage, all these parts have been
in as normal and unmutilated a state as possible, yet I
have never been able to see anything like the six develop-
ing bone-cells depicted and described by Professor Kolliker
in his manual of Histology, namely, “simple bone-cells ;
compound ones running to a parent-cell, with two secon-
dary cells, each arising from free cells,from rickety bone,” p.
84, English translation. (It would have been better if Pro-
fessor Kolhker had selected specimens intended to illustrate
the normal structure of healthy bone, from sound rather
than from rickety bone. Are specimens of developing bone-
cells, exhibiting the appearances represented in the plate
alluded to, so difficult to be obtained from an unsuspected
source, that Professor Ko6lliker is obliged to get them
from a suspected one? At any rate, this is not the
simplest way of prosecuting the mquiry. By employing
a tissue im an abnormal state to illustrate its normal

ES GS Se a Mn Chai cas Et i 1 2 nial anda ae

2 a SEO A eee og

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BY MOLECULAR COALESCENCE. Tk

structure, a new condition, or a fresh unknown quantity
is introduced into the problem; and it is exceedingly
doubtful whether a person prudently sceptical would not
on that account object to any conclusion arrived at from
‘such a mode of investigation, and more especially where
that conclusion is to serve as a foundation upon which the
superstructure of the histology of a part is to be erected.
We deduce the nature of a diseased structure by com-
paring it with a sound one, the latter being taken as the
exemplar. But Professor Kolliker reverses this mode of
procedure, and builds up his tissue of bone with materials
taken from the osseous tissue of a rickety subject. No
wonder, then, if his histology of this structure partakes
also of the abnormality of the elements of which it is
composed.) All that can be seen in the very earliest
stage of the ossific process are minute particles of earthy
matter, which, from their number, cannot possibly be
germs of cells, nor, from their size, can be regarded as
perfectly formed cells; but they are, notwithstanding,
particles of osseous matter; hence, it is clear that the
production of bone is antecedent to, and independent of,
either secreting cells or cell-germs. And besides, these
particles, by a careful and proper mode of examination,
can be seen to produce, by their union, lacunz ; conse-
quently the lacunz, instead of bemg a system of organs
designed to produce bone, that is, instead of being the
vital cause of the elaboration of the primary osseous par-
ticles, are only the effects of a subsequent arrangement
and union of these same particles. So that the micro-
scopic appearances presented by the earliest stage of the
formation of bone in nowise agree with the cell-germ
theory. A great deal of importance is attached by phy-
siologists and pathologists, to the existence of a certain

122 FORMATION OF SHELLS OF ANIMALS, ETC.,

granule or granules in all kinds of corpuscles, their
presence being always considered as a sure indication of
the vital formative capabilities of all corpuscles possessing
them; and hence, as might have been expected, they have
been diligently sought for in the lacune of bone. Professor
Kolliker observes upon this subject, that ‘the contents
of the lacunz, according to the later imvestigations of
Donders, Virchow, and myself, appear very closely to
resemble those of the cells of cartilages DURING LIFE;
that is to say, they are a clear, probably viscid fluid, with
a nucleus. If bone-cartilage be boiled in water or caustic
soda for one or two minutes, these nuclei often show
themselves very distinctly ; or opaque corpuscles make
their appearance, which must be regarded as the con-
tracted cell-contents, including the nucleus, and analogous
to the corpuscles in cartilage.” See English translation,
page 306. In this quotation, it is observed “that the
contents of lacunze resemble those of cartilage-cells during
life.’ Does this mean that the contents of both kinds of
cells are living when compared, or that only those of the
cartilage cells are? If the former is intended, the determi-
nation of this poimt appears to my common sense to be
entirely beyond the reach of experiment or accurate
observation. If the latter be intended, as I suppose from
the sequel, then the incongruity is greater than that just
complained of. There the observations referred only to
parts sound and unsound, here the comparison is between
living and dead ones. However, as it is a translation
that I am quoting from, where it is possible that the
meaning of the original may not_be exactly rendered, so
that this perhaps is not the precise meaning of the author.
Now I may observe, with respect to the existence of any
particular granule or nucleus in these lacunz, that I have

cs - 1 aah eg at a ESE a
St a a Rg NC OS a ES a St I Ol OIE Ca te A lL ae

BY MOLECULAR COALESCENCE. 12a

myself seen nothing that struck me as giving them the
appearance of nucleated cells, that is as compared with
typical forms of these cells, such as the germinal vesicle
of the mammal, or the caudate cells occurring in the grey
cerebral substance. Indeed they have always appeared to
me, excepting as occasionally represented in plates, to be
most uncell-like, which from the observation just quoted
ought not to be the case. For the contents of the lacunz
being represented as clear, the nuclei contained therein
ought to have been distinctly visible without the severe
expedients of fire and caustic. And then, after boiling the
bone in caustic soda, Professor Kolliker observes, as a quod
sequitur, that the opaque corpuscles which make their ap-
pearance must be regarded as the contracted cell-contents,
including the nucleus. Now to me the more probable
inference would be, that a nucleus, so delicate as to be
before invisible or only dimly seen, would by such rough
treatment have been utterly annihilated; and that the
granular material remaining after the coction would have
been so ill-defined and irregular in its form as to allow of
being considered anything which the experimenter wished.
As for my own opinion upon the subject, I state positively
that if the experiment had been mine instead of Professor
Kolliker’s, I should have considered the result to be of no
value whatever.

I know of no part in which the true nature of lacunz is
so manifest as in the osseous lamine spiralis of the
human subject. This part consists of two very thin plates,
partially separated by canals containing the cochlear
nerves. If a detached portion of one of these plates,
where it is thinnest, be examined by the microscope, it will
be seen to be perforated by oval spaces of different sizes,
corresponding to the osseous lacunee or bone-cells of the

124 FORMATION OF SHELLS OF ANIMALS, ETC.,

denser parts of this organ. The piece of lamina spiralis
thus perforated has the appearance of a fragment of a
foraminiferous animalcule. -This form of lacuna seems to
arise simply from the thickness of the plate of bone at this
part being less than the transverse diameter of an ordinary
lacuna, so that organs like these, complete in all their
dimensions, would have, in such situations, presented a
number of bulgings on the surface of the osseous lamina,
instead of rounded or oval spaces penetrating entirely
through it. Now, if the function of these parts had been
of vital importance, is it not more probable that they
would have retained their integrity at so apparently
inconsiderable a sacrifice, than that they would have been
thus mutilated? Perhaps the identity of these foramina
with lacunze will not be admitted ; then, as there is nothing
else connected with these plates of bone which can be
taken for bone-cells, the only conclusion to be arrived at
would be that they were formed without the instrumentality
of any such organism ; and thus fresh testimony would be
added to that which has been already adduced, to prove
that the form of osseous tissue, called by physiologists
lacune or bone-cells, is not endowed with the vital power
of forming bone, being itself a secondary and not a
primary formation. Now, as the identity of these
openings with true and perfect lacunz can scarcely be
questioned, the last supposition is not likely to be generally
maintained ; and as the improbability of their function as
formative organs will be shown better by considering
what lacune are, than what they are not, I will proceed
to the consideration of what appears to me to be their use ;
both as they exist in the form of foramina in the lamina
spiralis, and as minute cavities elsewhere. Now bone,
like every other form of organized tissue, is in no part of

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BY MOLECULAR COALESCENCE. 125

its structure absolutely solid; consequently vacuities or
interstices are an essential part of its morphology. Hence,
one purpose answered by lacunz in common with Haversian
canals, medullary passages, and cavities containing medulla,
is the prevention of a degree of solidity which would be
incompatible with its nature as a constituent of an
organized body. It is true that some of these spaces
contain fat, and give passage to vessels, so that they have
a twofold use; but the others not containing these
structures answer only to the one purpose here mentioned,
which admits of positive and certain proof. From these
considerations then, I hold it as a demonstrated fact that,
at least, one use of the lacune of bone is to prevent such
a degree of approximation of the particles of the earthy
matter of which it is composed as would be incompatible
with its very organization. It now remains to examine
how far this inferred fact agrees with the general and
intimate structure of bone. A careful comparison of the
vacuities in different parts of a bone, and in the bones of
different classes of animals, will show that one description
of space insensibly merges into another, and therefore
that there is only one cavity in a bone whatever may be
its magnitude, and the complexity of its form, and that
the Haversian canals, lacune, and canaliculi are merely its
prolongations, assuming various shapes and sizes in dif-
ferent parts of a bone, according as circumstances may
require. The transition of the central medulla-canal m
the shaft of a cylindrical bone into the irregular passages
contained in its expanded ends; and the gradual diminu- —
tion and conversion of these into the larger Haversian
canals, is too obvious to need any further notice. But the
transition of Haversian canals into lacune, and of these to
canaliculi, will require the aid of the microscope, and the

‘

126 FORMATION OF SHELLS OF ANIMALS, ETC.,

comparison of these parts in bones of different classes of
animals. The bone of fish, presenting the greatest
irregularity in structure, is well adapted for the demon-
stration of this fact ; and I know of no part better than the
caudal fin-bone of the anchovy, simply cleared of the
surrounding structures, and examined in water or glyce-
rine. In some parts of this bone irregular spaces occur,
of a form inclining to that of an ordinary lacune, and
with canaliculi branching out from them ; but they directly
communicate with, and are of about the same size as, a
small Haversian canal; so that, partaking equally of the
character of both, it is not possible to determine whether
they ought to be considered as belonging to the former or
to the latter named parts. In other parts of the same
bone minute spaces are seen, presenting fusiform enlarge-
ments, but prolonged at each end into a filiform
structure. Some passages of a similar kind have no
distinct enlargement, but continue nearly of the same size
until they inosculate with canaliculi from other lacunee of a
more characteristic form. In such instances the dis-
tinction between canaliculi and lacune is so obscure that
one cannot be distinguished from the other. These facts
show that such spaces and interstices are of no vital
importance, and agree with the general inference
that they merely serve to give lghtness to the
denser parts of bone, and thus their office in the
osseous tissue seems to be analogous to that of the
meshes or areolz in other tissues of mferior density, such
as hgaments, tendons, &c. which are composed only of
fibrous material, which itself in a modified form enters
also largely into the composition of the hardest parts of
the densest bones. The correctness of this view is cor-
roborated by the structure of the lamine spiralis, as just

.
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ee eee

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BY MOLECULAR COALESCENCE. 127

described. The foramina in the osseous plates of this
part replacing the lacune as found in other bones, and
presenting a decided form of osseous areolar tissue. It is
also still more corroborated by the areolated character of
the osseous tissue, evident in a very early stage of develop-
ment of the flat bones, as those of the cranium of feetal
animals. In this case the recently ossified membrane has
the appearance of being made up of meshes of various
sizes produced by the interlacement of its fibres. The
smallest meshes correspond to the lacunze of perfect bone,
and appear to result from the plaiting or interlacing of
the individual fibres; the largest ones corresponding to
Haversian canals, are of very different sizes, and seem to
be formed by a similar interlacing of fascicule of these
fibres. This appearance is very distinct in the ossifying
cranial bones of a very young pigeon; also in those of
the human foetus at a very early period. The part where
the ossifying process is just beginning to encroach upon
the membrane, shows this fact most clearly. No prepara-
tion is necessary beyond removing the integument, and
putting the part into water or glycerine. The part of
the process of ossification next to be considered relates
to the chemical conditions under which the earthy matter
is produced, and precipitated in a globular form. Now,
as bone in most parts of the animal body is placed under
the same anatomical conditions as the plates of shell,
which, in the larger crustaceans, afford attachment to
muscular fibres; and as the surface of the latter can be
proved by proper tests to be moistened with a solution of
an alkaline carbonate, and thus to be provided with one of
the elements of which shell is formed ; and as it is shown
that the other elements are brought into contact with the
former through the medium of the circulating fluid where,

128 FORMATION OF 8HELLS OF ANIMALS, ETC.,

there results, after their decomposition, not only the
necessary combination of lime with carbonic acid, but a
compound containing also the requisite animal matter, it
may be inferred that the coalescing particles of a similar
composition, demonstrable on ossifying membranous
tissues, are formed precisely on the same principles, the
membrane on which the phosphate and carbonate are
precipitated presenting the alkaline carbonate, and the
blood furnishing the earthy compounds. As respects the
precise manner in which the alkali, demonstrable in the
crustacean, is produced, there is the same difficulty in the
vital theory as in the physical explanation, and for the
present both are equally inexplicable. However, it is
much more probable that the production of this alkaline
carbonate should be the effect of electricity, than of the
direct agency of life. Electricity is a well-known decom-
posing power, and electrical combinations are sufficiently
common in animal bodies. The electric power of the
torpedo may be taken as an example, but I am not aware
that there is any proof that life, acting by itself, ever pro-
duced any of those phenomena which can be exhibited
experimentally on inanimate matter. Now, im the process
of calcification, as in that of ossification, the carbonate
and phosphate of lime are always precipitated on a mem-
branous tissue of some form or other, either presenting
markings or wholly homogeneous, this depending upon
some particular function performed by the membrane, and
not at all connected with the formation of shell or of bone.
For, however disimilar these membranous structures are
in different parts of the same animal, or in different
animals, the deposit in its primary condition is always the
same. After the first precipitation and coalescence of the
earthy matter, either in the form of rings, or in that of

i eee

el Et IN TI Tt

BY MOLECULAR COALESCENCE. 129

arches is completed, the membrane on which this process
has taken place becomes completely covered with a layer
of bone; and thus is formed the outermost circle of an
Haversian canal, consisting externally of a layer of mem-
brane, and internally of one of bone. Within the latter
another layer of membrane is formed, which becomes
coated in the same manner by a layer of bone, and thus
the process is repeated until the Haversian canal is com-
pleted. Now this arrangement of alternate layers of
bone and membrane can be seen by polarized light
distinctly in thin transverse sections preserved in Canada
balsam or glycerme, by polarized light, the osseous portion
appearing white, and the membranous, not polarizing the
light, black. A difference of structure, as first pointed
out by Tomes and De Morgan, can be distinguished also
by the ordinary illumination, one layer presenting a more
granular appearance than the other. These lamella are
seen distinctly only in the higher mammalians. They are
scarcely recognisable in the bones of cetaceans, and in
those of birds they are absent altogether. A similar
irregularity occurs also in respect to the lacune, canaliculi,
and Haversian canals. The lacune and the canaliculi
connected with them are subject to every possible
degree of variety in different classes of animals. In
the higher mammals the form of the lacunze is some-
what elliptical, and the canaliculi proceeding from
them take chiefly two directions, namely, towards the
centre, and towards the circumference of the Haversian
system to which the lacune belong. In birds, especially
the high flying ones, as the condor and albatross, the
lacunee are generally very small and of no particular form,
and the canaliculi, which are also very minute, diverge
from them in all directions, and, communicating very
9

130 FORMATION OF SHELLS OF ANIMALS, ETC.,

freely, appear to enclose in their circular meshes the
rounded, osseous particles of which the bone is composed.
In the bone of the palate of the Myliobatis, the lacunz
appear to be replaced by Haversian canals, from which
very large canaliculi proceed, so that there being only one
set of passages besides canaliculi, either lacune or Haver-
sian canals must be wanting. The Haversian canals, and
Haversian systems, as they are called, present great variety.
Some of the most irregular and ill-defined of these canals
are called Haversian spaces. As to the Haversian system,
it may be observed that in some bones they are distinct,
and separated by interstitical portions of osseous tissue ;
but, in others, as in those of the bird, they are blended
together. Besides, in the bones of fishes generally, and in
some of those of the larger reptiles, as the crocodile, one
part of a specimen will present Haversian systems, whilst
in other parts they are altogether absent. Lastly, as a
specimen of bone remarkable for the irregularity of its
various component structures, [ may mention the cementum
of ruminants, which often presents Haversian canals,
lacunee, and canaliculi, all of the most irregular and ap-
parently abnormal character. Indeed, thin sections of
some of the densest of the sclerous vegetable tissues have,
excepting the fact of the total absence in those of Haver-
sian canals, as much the appearance of ordinary bone as
this substance. And in good specimens of the sclerous
tissue in progress of development, the lacunz and cana-
lieu can be seen to be formed by the partial coalescence
of previously existing sclerogen particles, in the same
manner as was noticed of the osseous particles, when de-
scribing the lacune and canaliculi of bone. ‘The inner-
most portion of the shell of the unripe peach-nut is well
adapted for the examination of this process, especially if

a

BY MOLECULAR COALESCENCE. 131

the part be examined in glycerine. And, as this tissue
polarizes light much better than the phosphate of lime,
either in perfectly or imperfectly formed bone, the polari-

‘scope can be employed with greater advantage in inves-

tigating the structure and the mode of formation of this
form of vegetable tissue than in bone. I have merely
mentioned this vegetable substance incidentally, being
led to it by its resemblance to bone ; but I hope to consider
it more fully at some future period. I shall next proceed
to consider the formation of some of the less dense kinds
of tissue. Having, in the preceding pages, shown, as far
as experiment and induction can show, that the molecules
of what are called hard tissues, owe their curvilinear dis-
position to the direct operation of physical force, it may
reasonably be expected that the molecules of the less
dense ones owe their curvilinear arrangement to the same
cause, and that the process of coalescence above de-
scribed is as applicable to soft as to hard tissues, whether
they be animal or vegetable provided only, in both cases,
these molecules are brought under circumstances alike
favorable tor its operation. As it is certain that the ele-
mentary constituents of these two classes of tissues, before
they are combined to form living organs, are alike affected
by gravity, it is inconceivable, that a difference in this
respect should be occasioned merely by these same ele-
ments being associated with different proportions of fluid,
or that the molecules composing a spherule of globular
carbonate of lime, and those composing a spherical particle
of mucus, should, under similar circumstances, be brought
exactly into the same form by the agency of the most
dissimilar forces; and more especially, as it has been
shown by the plainest arguments, that, the force of gravi-
tation being all that is necessary to give the particles

132 FORMATION OF SHELLS OF ANIMALS, ETC.,

of matter exposed to its full influence their globular form,
any assumed vital interference, would be superfluous and
inconsistent. Dr. Carpenter observes, in reference to one
form of shell-structure, the prismatic cellular substance,
“that such is its resemblance to mucous membrane that it
may be considered in the light of a calcified epithelium.”
With this resemblance in structure, no doubt Dr. Carpenter
would include the idea of identity of the forces employed
in their formation. There are, however, two other struc-
tures, one hard and the other soft, whose resemblance
is more striking than that named by Dr. Carpenter, which
I will briefly consider. One is the common integument of
mammals; the other the dermic part of the shell of crusta-
ceans. In both there is a deep-seated layer of membrane
—basement membrane—in contact, by its superficial sur-
face, with rounded particles of various sizes; next above is a
layer of globular bodies containing granules of different
forms and magnitudes ; and, lastly, a covering of scales
or lamin, this depending upon circumstances. Now,
organs with so many points of resemblance in structure,
and both performing the same function, would be ano-
malous, if they were formed upon an entirely different
plan, and under the influence of agencies of a diametrically
opposite character ; that is to say, if the component ele-
ments of the former should owe their globular form to a
vital force residig in these globules, whilst it has been
demonstrated, that the elements of the latter owe their
arrangement in the same form to a force entirely phy-
sical; and the more especially so, as there is no other dif-
ference in these tegumentary structures, but that occa-
sioned by the presence of carbonate of lime im the one,
and its absence from the other. However anomalous it
may appear that two such organs as those just mentioned

EE

BY MOLECULAR COALESCENCE. ldo

should be formed on different principles, it would appear
much more so, if these two opposite principles were em-
ployed at the same time in the formation of different parts
of the same integument, this could not fail to be the case in
the skins of those reptiles, which, as in the toad, contain
in some parts, carbonate of lime, resembling shell, whilst
in other parts this substance is entirely absent. See a
paper of mine on the Skin of the Toad in the ‘ Micro-
scopical Journal.’ I may notice here, that this explana-
tion is intended to apply only to the histology of tissues,
and not to their physiology; that is, to the manner in
which they are formed, and not to the manner in which
they act. ‘To take im illustration of my meaning the three
kinds of corpuscles—the common mucous corpuscles, the
ciliated mucous corpuscles, and the cerebral corpuscles, I
may observe that, although I consider each kind to aec-
quire its form by the operation of the same physical
force, and that this force, in all of them, acts exactly
in the same manner, I do not by this intend to imply,
that the function of each, whether obscure or patent, is
necessarily a physical phenomenon,—this is not a part of
the subject-matter of these researches. However, if the
cause of these phenomena is physical, it is certain that
the manner in which they are produced would require for
its comprehension a knowledge of the different depart-
ments of physical science,—chemistry, electricity, and
the molecular condition and capabilities of matter more
refined and more extensive than is at present possessed by
philosophers. And as life, considered abstractedly, is
altogether incomprehensible by our senses, it is probable
that all future advances in physiological science will be little
more than fresh disclosures or clearer views of physics and
the sciences therewith associated, as connected with orga-

134 FORMATION OF SHELLS OF ANIMALS, ETC.,

nized bodies. This view has certainly the sanction of expe-
rience. As respects the fact of coalescence in soft structures
I may observe, that the proofs cannot be expected to be so
demonstrable as in hard ones, in consequence of the pro-
cess being in the latter sufficiently slow and gradual to afford
ample opportunities of observing it through all its stages,
whilst in the former it would take place too suddenly to
admit of being observed in detail, one part of the process
following so closely upon the other as to be distinguishable
only as one physical act; consequently, im the case of
coalescence of the softer tissues, other evidence besides
that furnished by microscopical examination must be
resorted to. Hence, I may observe that the words hard
and soft are merely relative terms, implying different
degrees of cohesion ; and therefore, as it cannot be sup-
posed that the physical forces acting upon the particles of
the harder substance, and leading to their coalescence, can
be different, or can act differently upon the particles of
the softer ones, leading precisely to the same result,
(namely, in both cases to the like incorporation of smaller
particles into larger ones,) the process of coalescence in
both substances must be identical. I may notice also, m
reference to the appearances presented by growing car-
tilage—this being a structure in which development by
self-multiplication of its cells is considered to be well
marked—that if an isolated piece of cartilage in this state
were examined with the microscope, by the side of
some coalescing globules of carbonate of lime, it would be
Just as difficult, in the one case as in the other, to say,
from mere inspection, whether the larger rounded particles
are the result of coalescence, or of cell-multiplication by
division. However, if the slide containing the globules of
carbonate of lime be so moved that the smaller globules

BY MOLECULAR COALESCENCE. 135

can be seen with the larger ones, then the nature of the
appearance becomes obvious. Just so with the growing
piece of cartilage. When it is so shifted that its growing
circumferential part is brought into view, the corpuscles
can be observed gradually to become smaller and less
perfect as they approach the margin; therefore giving in
this respect the same evidence of coalescence as the
globules of carbonate on the slide, on which the larger are
known to be formed by the union of the smaller. Besides,
if the growing circumferential part of this piece of car-
tilage had increased by the addition only of cells dividing
each into two, and these again, after having attained a
state of maturity, dividing each into two more, and so on,
the margin of the cartilage ought to give much better
indications of the fact than the central portion, whereas
the reverse is the case, the margin presenting nothing but
small, incomplete, and irregularly shaped particles. The
growth of cartilage, as here described, can be very well
seen in the extreme phalanges of the toes of a frog whilst
in progress of development from the tadpole-condition.
But cartilage, being made up of particles, sometimes not
very dissimilar to those of the surrounding parts, is not so
well calculated to give positive evidence either in favour of
one or the other view of development, as some other soft
structures—as, for example, the branched pigment-cor-
puscles. I have chosen these corpuscles for examination,
these being formed by the aggregation of opaque black
particles, can be distinguished in a very early stage, and
when their size is very small; corresponding in this respect
with the calcareous particles of shell and bone. The
accompanying plate (see fig. 9) 1s an accurate representa-
tion of these so-called cells, as seen in the periosteum of
the fang of a tooth taken from a foetal calf. In this

136 FORMATION OF SHELLS OF ANIMALS, ETC.,

specimen the isolated particles of pigment can be seen
either scattered about irregularly, or arranged in lines,
prior to their union to form a corpuscle ; hence these irre-
gular bodies furnish the same evidence of being formed by
the union and coalescence of pre-existing particles, as the
irregular stellate earthy bodies before noticed in shells
and bone do. Whilst there is nothing in their appear-
ance which can give the least semblance of probability
to the generally received opinion that the branched and
dotted lines, as represented in the figure, are offsets or
shoots from a central formative organ or cell-germ. I
may observe that I have the specimens from which the

Fic. 9. drawing was taken, and that

~ similar ones can easily be

oe obtained from very young
ene “eghonns? animals, especially from rep-

ee ele len ‘ tiles and fish, and from the
one git Alita lao hus choroid coat of foetal mam-
jal 0a > (Ce = mals. Also examples of
Thr et hd ne molecular coalescence in the
un ey softer tissues, equally strik-

oe if ing, can be seen in the
Oeste developing -hooklets of the

cysticercus cellulose as
described by me in a paper in the ‘ Philosophical Transac-
tions’ of 1857. These organs bemg composed of a very
highly refractile material, dissimilar in appearance to the
adjacent structures, can easily be distinguished in very
minute quantities; and these having a spherical figure,
admit of being traced through all the changes of form
attending the coalescence of the first visible particles,
up to that of the recognisable parts of a hooklet. The
following is the description of the development of these

BY MOLECULAR COALESCENCE. 137
organs, from the paper just referred to, written as early as
1855, before I was acquainted with the coalescing property
of the globular carbonate of lime. “The primary con-
dition of these hooklets is very remarkable, consistmg
merely of a confused and irregular group of very bright
particles of a pale straw-colour, which are of various shapes;
but still all have a contour more or less curvilinear, and
the smaller ones are of a spherical figure. Their size varies
from about that of the third part of a handle of a perfect
hooklet, to a particle so minute as scarcely to be appreci-
able by the highest powers of the microscope. There are
all the intermediate sizes between these extremes. Not-
withstanding, however, these extremes of size and form,
all these particles possess the same optical and physical
properties, so as to be perfectly recognisable both when
apart and when joined together in the perfect hooklet, in
which the larger pieces, formed obviously by the coalescence
of smaller ones, can be seen fused (as it were) together, more
or less completely in a newly-formed hooklet, where
frequently the joining is so incomplete as to amount to
little more than mere apposition of the coalescmg parti-
cles.’ Now, I may observe that there are only two
interpretations which can be given of these appearances.
Either they are in reality what I have described them, or
they must be hooklets in a state of degeneration, that is
undergoing a process of molecular disintegration. The
examination by the microscope would furnish no clew to
the correct decision of this question, as the microscopic
appearances would, in either case, be similar. But, as it
can be seen by referring to the original paper, that this
appearance cannot reasonably be supposed to be due to
degeneration, it may be inferred in this case to be indica-
tive of coalescence. For, in the first place, the cysticerci

138 FORMATION OF SHELLS OF ANIMALS, ETC.,

were in a very early stage of development, as can be seen
by their size, which in the plates in the ‘ Philosophical
Transactions’ is given, and the figures represent entire
animalcules; also, by the diminutive size of the part
containing the calcareous particles, called the neck, which is
an infallible proof of their immaturity, being, in these
specimens, scarcely at all developed ; and by there being,
in two of them, only a few of the hooklets, the regular
number in the perfect animalcule being twenty-six; and
in the second place, I may observe, that the hooklets,
which are represented in the plates, were not detached, but
are drawn as they were seen in their natural situation in
the unmutilated animalcules. And having besides the
specimens by me from which the drawings were taken, I
am enabled to give satisfactory proof that neither the
descriptions nor the plates are made up partly from facts,
and partly from imagination. I may also notice, that it
would not have occurred to me that these changes could,
by any one, ever have been attributed to a state of degene-
ration occurring, as they do, in eysticerei which had not yet
got the full number of these organs, had it not been stated
that such was the explanation given by some pathologists.

The next part, showing the fact of molecular coales-
cence, which I shall describe, will be the crystalline lens ;
and, in examining its true structure and mode of forma-
tion, I shall follow the same rule as that observed in the
other tissues, namely, that of selecting such specimens as
will afford the best opportunity of seeing, in as natural a
state as possible, the earliest stage of its development, and
the changes of structure dependent thereon, without the
necessity of employing such chemical substances, or
mechanical mutilation as cannot fail to render the ap-
pearances presenting themselves during the examination

BY MOLECULAR COALESCENCE. 189

unnatural; and thus more likely to give false ideas than
correct views of the structure of this organ. Of all the
lenses which I have examined, I have met with none
which answers the purpose so well as the lens of a young
stickleback, of about three quarter of an inch or an inch
long, but it should not be more. This part bemg of small
size, admits of beimg seen entire without any further
dissection than that necessary to remove it from the eye
of the animal, and can be examined perfectly fresh, which
in this case is indispensable; and as these animals are
everywhere to be met with, the examination is within the
reach of any one disposed to make it. Besides, I may
observe, that if it be done with sufficient care, and not in
an imperfect manner, as too many microscopical ex-
aminations are, it exhibits some most interesting
and beautiful physical facts. The following is ‘the
manner in which the examination may be conducted.
The head must be taken off whilst the animal is alive,
and an eye removed without delay, which, being torn
open by a sharp scapel, the lens enclosed in its cap-
sule will escape, and is to be put immediately into a
shallow cell filled with water, then a thin glass cover being
placed over it, it must be examined at once. A half-inch
lens at first, and afterwards a quarter-inch, are the
best magnifying powers for the purpose, and it will, of
course require to be seen by transmitted light. I may
observe that the lens of this fish is nearly of a spherical
figure, and that it is divided into an equator and two poles,
the plane of the former being at right angles with that of
the latter. The superficial layer of fibres, those especially
requiring notice, and proceeding from each side of the
equator towards the poles, may, from this circumstance,
be divided into an anterior and a posterior set, each

140 FORMATION OF SHELLS OF ANIMALS, ETC.,

covering its respective hemisphere, and converging towards
its pole, near to which the fibres appear to dip into the
substance of the lens, and insensibly to blend with the
nucleus. Now, to obtain the best view of these fibres,
and the manner in which they are formed, the lens, whilst
being examined, must be placed with either its anterior
or posterior surface towards the observer, and with its
polar axis corresponding to that of the microscope. In a
few seconds after the lens, still enveloped by its capsule,
has been in the water, the latter will become visibly in-
creased in size, and a space will begin to appear around
the edge of the lens, between it and the inner surface of
the investing capsule. The lens itself will also become
enlarged, and continue enlarging, so long as it is acted
upon by the water, until its capsule, becoming incapable
of further distension, will burst, and the lens will be either
entirely or partially extruded. The time which will
elapse after the contact of these parts with the water
before this takes place, will depend upon the age of the
fish from which the eye was taken, varying from two
minutes in a very young fish, to five in an older one. It
is at once obvious, that this distension of the capsule, and
enlargement of the lens under these conditions, is the
effect of endosmose. If the examination is made before
any distension has had time to take place, clear, more
or less compressed globular particles of an oily-looking
fluid, and of very various sizes, will be seen through the
capsule lying close to its deep surface. As the distension
increases, a clear space around the margin of the lens,
between it and the capsule, comes into view, and the
before-named oily looking particles becomes more distinct,
having increased in size, and apparently in number. They
still present no kind of regularity either in shape, size,

BY MOLECULAR COALESCENCE. 14]

or position, excepting that they all have a rounded form,
and the same clear and pale aspect. By a careful adjust-
ment of the focus, rows of sharply defined lines placed
close together, and at right angles with the direction of the
lens-fibres, resembling the marking of very fine voluntary
muscular fibre, will be visible. (See c¢, fig. 10.) These
lines, however, are sometimes first distinguishable as long
closely set striz, running more or less parallel with the
surface of the lens. ‘This is not their natural appearance,
but arises from the rows being pressed together, and thus
the lines of several are made to appear continuous. Such
are the appearances visible beneath the capsule of the

Fig. 10.

lens prior to its becoming ruptured. ‘After this, all the
appearances above described become much more distinct,
and the causes producing them obvious. Fig. 10 is an
accurate representation of these parts, as seen an hour or
two after the bursting of the capsule, magnified three
hundred diameters, and drawn with the camera lucida.
In this stage of the examination, the oily-looking globules,
in their turn, have become very much enlarged, by the
endosmose still going on. These are indicated in the

142 FORMATION OF SHELLS OF ANIMALS, ETC.,

diagram by the lettera. Next to these are the globules
still somewhat compressed, but yet very much distended,
shown by the letter 6. Before the absorption of water
by these particles they were apparently empty, and the
walls of the contiguous ones being then in contact, the
transverse marking, before described, was produced. Still,
nearer the centre of the lens, the transverse lines re-
main; the sides of these globules having become adherent,
and consequently their cavities obliterated. (See letter
c.) And, lastly, again, nearer to the centre, all appear-
ance of lines, both transverse and longitudinal, has disap-
peared, and the structure is entirely homogeneous. This
part is not represented in the accompanying figure.
During the further distension of these globules the trans-
verse lines in some of the rows can be seen gradually to
disappear, and then these rows of compressed globules
assume the appearance of tubes with bulbous extremities.
It as this appearance which probably led Koélliker to
describe the ‘fibres of the lens as tubes, having thi
walls, which are flexible and soft, and possessed of a con-
siderable degree of toughness, with clear, viscous, albu-
minous contents, which, when the tubes are torn, escape
from them in the form of large irregular drops.” This is
just the appearance presented in the figure at a. Now,
as my own observations do not in the least agree with the
opiion expressed by Professor Kolliker, concerning the
origin of this albuminous fiuid, and the tubular character
of the fibres of the lens, and as these are points of great
importance in respect to the mode of its formation, I
cannot do less than give my reasons for differing from
so high an authority. Now, as this same clear, viscous
oily-looking fluid, although im smaller globules, is visible
through the capsule of the lens, and before it has become

BY MOLECULAR COALESCENCE,. 143

in the least distended, and where no mechanical injury
had been done to it, it may be concluded, that this is its
normal situation and natural appearances. And, more-
over, as in this case, no force could have been employed
either in kind, or in degree, sufficient to lacerate tubes,
whose walls were possessed of a “considerable degree of
toughness,” and thus cause the escape of their contents ; it
is impossible that vessels from which, under such circum-
stances, the contents had escaped, could have possessed
the property of toughness; hence, there is an evident
incongruity between the alleged fact of the toughness of
these vessels, and their rupture under the circumstances
here mentioned. Moreover, it can easily be shown by
examination of the lens, a short time after the rupture of
its capsule, that the “large irregular drops” referred to
by Professor Kolhker, have a diameter many times greater
than that of the fibres of the lens; and, consequently, if
these had been tubes, as there is no reason to suppose they
are, globules of such dimensions could never have been lodged
in their interior. It is, therefore, obvious, that the views
of Professor Kolliker concerning the minute structure of
the lens, being entirely at variance with facts, are un-
tenable. In concluding the account of these appearances,
I may observe that, as the form and size of many of the
parts extruded from the capsule of lens vary according
to the time the endosmose and consequent distension
has been in operation, the microscopical examination will
require to be made almost continuously. This is the only
way in which a correct knowledge of these appearances
can be obtained, as after the cessation of the endosmose,
the globular particles become granular, the transverse
marking indistinet, and the general aspect of all the parts,
with the exception of the dentated, fully formed fibres,

144. FORMATION OF SHELLS OF ANIMALS, ETC.,

confused and ill defined. The exact form of the lens in
these fishes, with the arrangement of its fibres, as given at
the commencement of this description, can be best seen in
eyes which have been kept in glycerine for several months.
In some specimens thus treated, the striz in that part of
the converging fibres near to the equator of the lens can
also be seen, but not sufficiently to give any idea of their
true structure, and nothing definite is observable of the
clear viscous, albuminous particles so distinct in the per-
fectly recent lens, these having become granular and
amorphous. I may mention, that in all the examinations
I have made of the lenses of these fishes, 1 have never met
with the layer of nucleated cells seen in the eyes of mammals
close to the deep surface of the capsule; in some stances
there have been regular corpuscles, but these were found
only occasionally, and without any definite arrangement
or situation; and I have no doubt but that they are acci-
dental, and are only the white corpuscles of the blood
which have escaped from the vessels ruptured in removing
the lens from the eye, especially as I have found the red
corpuscles with them. Having now described these parts
as minutely as appears to me to be necessary, also the
manner of examining the lens, both in its recent and pre-
served states, I will consider its development in relation
to the process of molecular coalescence. Now, connected
with the albuminous particles situated on the surface of
the lens, between it and its capsule, the following facts
require notice. First, their extremely variable size, the
smallest being too minute to admit of accurate measure-
ment, the largest, in the undistended condition, being
about s5/59th of an inch in diameter, and the rest being of
all sizes intermediate between these extremes. Secondly,
the perfect resemblance of these particles one to another

BY MOLECULAR COALESCENCE. 145

so far as is possible, considering their difference in size.
Thirdly, the same property possessed by all, of imbibing
water and swelling out to several times their original di-
mensions. And, fourthly, their identity in structure and
appearance with those which, after having become arranged
in lines, form the first portions of the radiating fibres of
which the future lens is to be composed. (See fig. 10, in
which some of these forms are represented after having
been acted upon by water.) The free particles of different
sizes above noticed, are not, however, shown in this figure.
Now, considering the appearances presented by these par-
ticles, and weighing all these circumstances together, it
is impossible to question the identity of the larger de-
tached globules with those which have become stationary,
and are beginning to take the lmear arrangement; and
therefore only one point remains to be determined, and
that is, whether the larger of the intermediate sizes of the
globular particles assumed that size at the instant of their
coming into existence, or whether they are the result of
the coalescence of pre-existing minuter forms of the same
composition ; that is, of smaller globular albuminous par-
ticles similar to those which are still present with them.
As the kind of evidence necessary to decide the question
is not in this case of the same demonstrative character as
that which was adduced in answer to a similar question
respecting the coalescence of small particles of carbonate
of lime to form larger ones (see page 12), its decision
must, in some degree, depend upon the relative value of
the evidence adducible on each side. Now, on the side of
coalescence there is—First, the fact before referred to,
showing that there is such a process as coalescence even of
the particles of hard substances. Secondly, that the
effects of this same process admit of demonstration in the
10

146 FORMATION OF SHELLS OF ANIMALS, ETC.,

calcareous particles of organized tissues. And lastly, that
there is ocular proof of the same process in softer sub-
stances, as shown in the development of the hooklets of
the Cysticercus cellulose. Whilst in support of the oppo-
site view, there is not one fact of a demonstrable character
which can be adduced; hence, with the entire weight of
evidence in favour of the coalescing process, its operation
maybe fairly considered here to be assatisfactorily proved in
reference to the formation of the crystalline lens as it has
been shown to be in the other structures which have been
described. But as these observations only apply to the for-
mation of the large albuminous globules, it will be neces-
sary to explain also the transformation of these globules
into transverse striz ; then the disappearance of these striz ;
after that the appearance of longitudinal zigzag lines be-
tween the converging fibres; and, lastly, the entire oblite-
ration of all marking at the central part of the lens. The
globules as thus formed appear then to be merely rounded
masses of an albuminous material, with a dense and very
dilatable exterior lamina. The greater density of this
layer is the natural effect of the attractive force to which
the formation of these, and all other globular bodies con-
structed in the same manner, and on the same principle, is
due. And without doubt this is the mode of formation of
the peripheral layer of all corpuscles which have received
the appellation of “cells,” this layer being the cell-wall,
or cell-membrane, as it is frequently called. These globu-
lar particles are, in the entire eye, contained in an elastic
capsule—the capsule of the lens—where, at first, they
are placed without any apparent order, but afterwards
they become arranged in converging lines. (See fig. 10.)
Now, as in the growing condition of the lens fresh por-
tions of solution of albumen, forming new globules, will

BY MOLECULAR COALESCENCE. 147

be constantly added to the contents of the capsule, the
globules must press one against another, and thus their
globular form is seen to become destroyed, and to be re-
placed by the polyhedral form. Besides this, it can be
seen by imspection of fig. 10 that they are smaller the
nearer they are to the centre of the lens, and appear to
have suffered compression, especially in the direction from
without to within, and therefore they must have lost some
part of their contents. Now the fact of these cells be-
coming so rapidly enlarged by the imbibition of water,
proves that they retain the albumen in solution, and only
lose the water; consequently, as their sides in their
natural state are brought nearer together, the fluid within
them must become more and more inspissated, until
nothing remains but their dense exterior and the portion
of albumen which was in solution in the original albumi-
nous globule. This portion of albumen now blending
with that which before formed the wall of the globule in
which it is contaimed, a permanent addition is made to
the radiating fibre of which the individual globules are
parts. The close apposition of the walls of a multitude of
such globules, with the inspissated solution of albumen
in their interior, constitutes the beautiful transverse
marking represented in fig. 10 c. And the fact of these
becoming separated by the imbibition of water is an
experimental demonstration, that the cause of the collapse
of these cells is the reverse of the effect produced upon
them by the action of the water as applied in the experi-
ment, namely, the loss of their fluid, probably by exosmose.
Whilst the transverse marking exists in the radiat-
ing fibres, no defined serration of their edges is ap-
parent, but as the transverse lines disappear in consequence
of the perfect blending together of the contiguous particles

148 FORMATION OF SHELLS OF ANIMALS, ETC.,

with their now solid contents, these edges become sharply
serrated. Lastly, in and towards the centre of the lens,
where the coalescence is complete, the dentate lines which
indicate the lateral extent of the radiating fibres become
obliterated, showing, at this part, a thorough incorporation
of the material of which they are composed, and with this
the process of molecular coalescence of the lens termi-
nates. Mr. Nunneley, in a paper contaimed in the
‘Quarterly Journal of Microscopical Science’ for April,
1858, gives a plate of the epithelial cells from the posterior
part of the capsule of the lens of a sheep, showing lines of
cells, concerning which he observes that “ were it not that
similar cells are found in Petit’s canal I should feel
inclined to think that they are not merely the means of
nutrition to the lens, but that they are lens-fibres in
progress of development.’ This observation seems to me
to show that Mr. Nunneley would have persisted in enter-
taining his first impression as to the nature of these cor-
puscles, which I have no doubt is the right one, had he not
been diverted from this view by some preconceived physio-
logical theory concerning the nutrition of the lens. The
dentate lines, corresponding doubtless to the radiating lines
of feeble attraction in the artificially formed calculi, are
the last to become obliterated; and this does not take
place until the predominant force is the attraction of
tenacity. These lines are distinctly serrated only in the
fish, bemg merely undulating and irregular im mammals.
The circumstance of irregularity in these lines, as con-
trasted with that of the artificial and some of the natural
products, is probably to be accounted for by the difference
of mechanical conditions under which in the two cases they
areformed. These conditions in the former,—the artificial
product—applying at the same time to the entire spherical

BY MOLECULAR COALESCENCE. 149

mass, but in the latter—the lens—being limited only to very
small portions of lens-substance. It must also be observed
that the process of coalescence is accompanied by a che-
mical change in these albuminous globules, as is shown
by boiling a lens for a considerable time in water, when
the peripheral and imperfectly coalesced portion will by
its opacity indicate the presence of coagulated albumen,
whilst the central and adjoining parts will retain their trans-
parency, thus seeming to partake more of the character of
horn than of coagulated albumen. Now, on reviewing this
account of the formation of the crystalline lens of the
fish by the process of molecular coalescence, and con-
trasting it with the simple manner in which artificial
globules of the same size, as well as the otolithes of
these same fish, are formed (which can be shown to be
formed by coalescence), this will appear to be a very
round-about way of making a globular body, which ac-
cording to the explanation of the mode of formation of
artificial and other calculi, seems possible by a method so
very simple and direct. And if such transparent globules
as those produced by the artificial process could have
served for the purpose of vision, this objection would have
been just. But these former giobules being of necessity
so formed that their centre is the least dense, and their
circumference most so,—a form of construction exactly the
reverse of that of the lens,—could never have sufficed to
bring the rays of light to a focus, and therefore they
would be totally unfit for vision. Hence when vitality is
engaged in constructing such a lens as that just described,
and the principle of universal attraction has to take chief
part in the process, the tendency of this attraction to form
just such a lens as that which would be constructed by the
artificial process will require at every instant to be opposed.

150 FORMATION OF SHELLS OF ANIMALS, ETC.,

(Indeed gravity is not a universal influence, if its operation
isto be excluded from the process bywhich the lensof the eye
is formed; and its laws are not those which mathematicians
and philosophers have unanimously considered them, if a
lens formed in complete obedience thereunto would not
have been, in respect to vision, a useless one.) Hence the
impossibility of anythimg short of itricacy in the
mechanism of an organ constructed under circumstances
where the principal force employed in the process is
always working in the wrong direction, and is therefore
requiring constantly to be opposed, and to be put imto the
right track. Now these ends seem to be attained in the
case of the crystalline lens, by its bemg composed of
globules of such a composition that they do not coalesce
until the more fluid part has been removed; and thus in
place of being made up at once of all the molecules
entering into the composition of the globules at first
collected together, as in the artificial calculi, it is formed
only by the gradual coalescence of their denser portions,
and especially of their outer lamime. Besides these
physical peculiarities, it has been observed that the
coalescence is accompanied by a chemical change in the
coalesced particles, as is shown by the fact of their
retaining their transparency after bemg boiled in water,
and by their density becoming increased as the coalescence
progresses, and attains its ultimate condition of com-
pleteness in the centre of the lens, an effect the opposite
of that which would have been produced by the uncon-
trolled action of gravity. Hence in the general arrange-
ment of the particles composing the crystalline lens, the two
attractions mentioned at pages 32 and 55—the attraction of
tenacity,and the attraction of gravitation—musthave acted
inversely as each other. But the latter being universal,

BY MOLECULAR COALESCENCE. 151

and unceasingly in action, would require no fresh arrange-
ment of conditions necessary for its production, whilst the
former being entirely a local influence, and exerted for one
purpose only, and with an effect varying at every instant,
would require the chemical condition upon which it depends
to be also constantly varying. Now, in the formation of the
erab- and oyster-shell these conditions, and the manner in
which they operate, are toa very great extent apparent ; but
in the case of the formation of the material composing the
lens, the chemical process is not, at least in the present
state of science, at all clear; and doubtless a most exact
chemical investigation, directed especially to this point,
would be required to make it so. However, one question
presents itself, whether, is that which has the power of bring-
ing together these conditions, chemical and mechanical, and
exactly adapting them to the necessities of the case, resi-
dent im and exercised by the material of the lens? or,
whether it is the effect of a separate and independent
principle, acting upon this material, through the instru-
mentality of well-known influences, called the properties of
matter? If the aflirmative is to be given to the first part
of this question, then I cannot see how it is possible to
deny the existence of an amount of intelligence and skill
in the cells of the lens of the eye of any being, infinitely
surpassing that of the individual to which it belongs. For
how could the particles composing these globules so regulate
their densityand curvature, that all the rays passing through
them should be brought colourless to one point, without
possessing a perfect knowledge of the laws of dispersion and
refraction of light? or, how could the developing particles,
occupying similar points on opposite sides of the axis of
the same lens, or points having precisely the same relative
position in the lenses of both eyes, preserve always a like

152 FORMATION OF SHELLS OF ANIMALS, ETC.

form and density, unless these developing globules were
severally acquainted with the changes of form and structure
going on simultaneously in all globules similarly situated ?
Whereas, if the affirmative be given to the second side of
this question, then the rounded form of the crystalline
lens will be due to the operation of the same physical
forces as that of the shells of molluses and crustaceans
before described. And so with respect to rotundity of
contour generally, organic will agree with inorganic
bodies; the spherical figure of both when placed under
circumstances where their component molecules are
affected more by the mutual attraction they have one
for another, than by that of remote objects being alike
dependent upon gravity ; and thus the analogy of nature,
in regard to this fact, is complete; and the same Infinite
power and wisdom which are displayed in the government
of the inorganic world according to fixed laws, are also
equally displayed in the arrangement of the material parts
of organized beings, according to the same laws.

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