Encyclopaedia Britannica > Volume 21, ROT-Siam

724 S E X-
that is to say, of anabolism and katabolism. Were these
steps made a new synthesis would be reached, and from
this point it should even next be possible to retrace the
progress of the science, and interpret the forms and the
functions of tissues and organs, nay, even of the facts of
aspect, habit, and temperament, so furnishing the deductive
rationale of each hitherto merely empirical order of ob¬
served fact and connecting theory.
While this conception does not admit of development within
the present limits,1 a brief abstract of such an interpretation of
reproduction and of sex in terms of anabolism and katabolism may
be of interest to the reader. The theory of reproduction, in
general principle at least, is simple enough. A continued surplus
of anabolism involves growth, and the setting in of reproduction
when growth stops implies a relative katabolism. This in short
is merely a more precise restatement of the familiar antithesis
between nutrition and reproduction. At first this disintegration
and reintegration entirely exhaust the organism and conclude its
individual existence, but as we ascend the process becomes a more
and more localized one. The origin of this localization of the
reproductive function may best be understood if we figure to
ourselves a fragment of the genealogical tree of the evolutionist in
greater detail, and bear in mind that this is made up of a con¬
tinuous alternate series of sex-cell and organism, the organism, too,
becoming less and less distinguished from its parent cell until the
two practically coincide in the Protozoa, which should be defined not
so much as ‘ ‘ organisms devoid of sexual reproduction ” but rather
as undifferentiated reproductive cells (protosperms or protova, as
they might in fact be called), which have not built up round them¬
selves a body. We should note, too, how the continuous immortal
stream of Protozoan life (see Protozoa) is continued by that of
ordinary reproductive cells among the higher animals, for the mor¬
tality of these does not affect this continuity any more than the
fall of leaves does the continued life of the tree. The interpreta¬
tion of sex is thus less difficult than might at first sight appear.
Por anabolism and katabolism cannot and do not absolutely bal¬
ance, as all the facts of rest and motion, nutrition and reproduc¬
tion, variation and disease, in short of life and death, clearly show.
During life neither process can completely stop, but their algebraic
sum keeps varying within the widest limits. Let us note the result,
starting from the undifferentiated amoeboid cell. A surplus of ana¬
bolism over katabolism involves not only a growth in size but a
reduction in kinetic and a gain in potential energy, i.e., a diminu¬
tion of movement. Irregularities thus tend to disappear; surface
tension too may aid ; and the cell acquires a spheroidal form. The
large and quiescent ovum is thus intelligible enough. Again starting
from the amoeboid cell, if katabolism be in increasing preponderance
the increasing liberation of kinetic energy thus implied must find
its outward expression in increased activity of movement and in
diminished size; the more active cell becomes modified in form
by passage through its fluid environment, and the flagellate form
of the spermatozoon is thus natural enough. It is noteworthy, too,
that these physiologically normal results of the rhythm of cellular
life, the resting, amoeboid, and ciliate forms, are precisely those
which we empirically reach on morphological grounds alone (see
Morphology, vol. xvi. p. 841).
Given, then, the conception of the cellular life rhythm as capable
of thus passing into a distinctly anabolic or katabolic habit or
diathesis, the explanation of the phenomena of reproduction becomes
only a special field within a more general view of structure and
function, nay even of variation, normal and pathological. Thus
the generality, use, and nature of the process of fertilization become
readily intelligible. The profound chemical difference surmised by
so many authors becomes intelligible as the outcome of anabolism
and katabolism respectively, and the union of their products as
restoring the normal balance and rhythm of the renewed cellular life.
Without discussing the details of this, farther than to note how
it resumes the speculations of Eolph and others as to the origin
of fertilization from mutual digestion, of the reproductive from the
nutritive function, we may note how they illustrate on this view that
origin of fertilization from conjugation which is the central problem
of the ontogeny and phylogeny of sex. The formation of polar
vesicles seems thus an extrusion of katabolic (or male) elements,
and conversely its analogues in spermatogenesis (see Eeprodttc-
tion). Passing over such tempting applications as that to the
explanation of segmentation and even subsequent developmental
changes, it must suffice to note that the constant insistance of
embryologists upon the physiological importance of the embryonic
layers bears essentially upon their respective predominance of ana¬
bolism and katabolism. The passage from ordinary growth to that
discontinuous growth which we term asexual reproduction, and from
this again to sexuality or the frequent reverse progress, is capable
of rational interpretation in like manner: the “ alternation of gene-
-S E X
rations” is but a rhythm between a relatively anabolic and katabolic
preponderance; a parthenogenetic ovum is an incompletely differ¬
entiated ovum which retains a measure of katabolic (male) products,
and thus does not need fertilization; while hermaphroditism is due
to the local preponderances of anabolism or katabolism in one set
of reproductive cells or in one period of their life. The reversion
of unisexual forms to hermaphrodite ones, or of these to asexual
ones, which we have seen in such constant association with high
nutrition and low expenditure,2 is no longer inexplicable. The
female sex being thus preponderatingly anabolic, the importance of
good nutrition in determining it is explained: menstruation is seen
to be the means of getting rid of the anabolic surplus in absence
of its foetal consumption, while the higher temperature and greater
activities of the male sex express its katabolic diathesis. The
phenomena of sex, then, are no isolated ones, but express the
highest outcome of the whole activities of the organism—the literal
blossoming of the individual life. (P. GE.)
SEXTANT, an instrument for measuring angles on the
celestial sphere. The name (indicating that the instru¬
ment is furnished with a graduated arc equal to a sixth
part of a circle) is now only used to designate an instru¬
ment employing reflexion to measure an angle; but
originally it was introduced by Tycho Brahe, who con¬
structed several sextants with two sights, one on a fixed,
the other on a movable radius, which the observer pointed
to the two objects of which the angular distance was to
be measured.
In the article Navigation the instruments are described
which were in use before the invention of the reflecting
sextant. Their imperfections were so evident that the
idea of employing reflexion to remove them occurred
independently to several minds. Hooke contrived two
reflecting instruments. The first is described in his Post¬
humous Works (p. 503); it had only one mirror, which
reflected the light from one object into a telescope which
is pointed directly at the other. Hooke’s second plan
employed two single reflexions, whereby an eye placed at
the side of a quadrant could at the same time see the
images formed in two telescopes, the axes of which were
radii of the quadrant and which were pointed at the two
objects to be measured. This plan is described in Hooke’s
Animadversions to the Machina Coelestis of Hevelius, pub¬
lished in 1674, while the first one seems to have been
communicated to the Royal Society in 1666. Newton
had also his attention turned to this subject, but nothing
was known about his ideas till 1742, when a description
in his own handwriting of an instrument devised by him
was found among Halley’s papers and printed in the
Philosophical Transactions (No. 465). It consists of a
sector of brass, the arc of which, though only equal to
one-eighth part of a circle, is divided into 90°. A tele¬
scope is fixed along a radius of the sector, the object glass
being close to the centre and having outside it a plane
mirror inclined 45° to the axis of the telescope, and
intercepting half the light which would otherwise fall on
the object glass. One object is seen through the tele¬
scope, while a movable radius, carrying a second mirror
close to the first, is turned round the centre until the
second object by double reflexion is seen in the telescope
to coincide with the first.
But long before this plan of Newton’s saw the light
the sextant in its present form had been invented and had
come into practical use. On May 13, 1731, John Hadley
gave an account of an “octant,” employing double re¬
flexion, and a fortnight later he exhibited the instrument.3
2 Thus Marshall Ward has lately drawn attention to the association
of parasitism with the disappearance of sexual reproduction in Fungi
{Quart. Jour. Micr. Sci., xxiv.).
3 Hadley described two different constructions : in one the telescope
was fixed along a radius as in Newton’s form, in the other it was
placed in the way afterwards universally adopted; an octant of the
first construction was made as early as the summer of 1730, according
to a statement made to the Royal Society by Hadley’s brother George
on Feb. 7, 1734.
1 See paper by Geddes already nientioned at p. 721, footnote.