The black represents the cuticular product of the epidermal cells of the ocular area, taking the form either of))...,r,, f lens, cl, of crystalline body, cry, or of rhabdom, rhab; hy, hypodermis or epidermal cells; corn', laterallyplaced cells in the simpler stage, A, which like the nerve-end cells, vit' and ret', are corneagens or lens-producing; corn, specialized corneagen or lens-producing cells; vie, potential vitrella cells with cry', potential crystalline body now indistinguishable from retinula cells and rhabdomeres; vit, vitrella cell with cry, its contained cuticular product, the crystalline cone or body; ret', rhab', retinula cells and rhabdom of scorpion undifferentiated from adjacent cells, vit'; ret, retinula cell; rhab, rhabdom; nf, optic nerve-fibres.
We shall, therefore, ignoring the ocular somite, speak of the first, second, third, fourth, fifth and sixth legbearing somites of the prosoma, and indicate the appendages by the Roman numerals, I, II, III, IV, V, VI, and whilst ignoring the praegenital somite we shall speak of the first, second, third, &c., somite of the mesosoma or opisthosoma (united mesosoma and metasoma) and indicate them by the Arabic numerals.
The intra-ocular tension is markedly lowered.
Apart from the possible existence of an ocular ep FIG.3.
Occasionally the ocular lobes are articulated.
Spiritualists have, as a rule, sought to convince not by testimony but by ocular demonstration.
A, Anterior ocular or orbital, or praeorbital or anteocular.
It is used in all cases where one needs to reduce the intra-ocular tension, and for this and other reasons in glaucoma.
These will then remain as typically composed each of six appendage-bearing somites - the prosoma comprising in addition the ocular prosthomere.'
Usually the sides of the carapace are strangely produced into a mock rostrum in front of the ocular lobe, be it oculiferous or not.
One of these is the ocular segment, in front of the antennal, and behind the primitive preoral segment.
A somite placed between the prosoma and mesosoma - the prae-genital somite - appears to have belonged originally to the prosomatic series (which with its ocular prosthomere and palpi FIG.
If a telescope be employed there is a distinction to be observed, according as the half-covered aperture is between the eye and the ocular, or in front of the object-glass.
Again, in an ocular heliometer by Steinheil double image is similarly produced by a divided prism of total reflection placed in parallel rays.
He endeavoured to illustrate the subject by a clavecin oculaire, or ocular harpsichord; but the treatise and the illustration were quickly forgotten.
By suitably replacing the ocular of the observing telescope in an angular vision spectroscope by a photographic camera, it is possible to photograph spectra; such instruments are termed spectrographs.
The sight of many an eye has been destroyed by the use of atropine - in ignorance of this action on the intra-ocular tension - in cases of incipient glaucoma.
The fourth ocular result of administering atropine is the production of a slight but definite degree of local anaesthesia of the eyeball.
The drug is often replaced in ophthalmology by homatropine - an alkaloid prepared from tropine - which acts similarly to atropine but has the advantage of allowing the ocular changes to pass away in a much shorter time.
But the protocerebrum contains the ganglia of the ocular segment in addition to those of the procephalic lobes.
It seems that confusion and trouble will be best avoided by abstaining from the introduction of the non-evident somites, the ocular and the praegenital, into the numerical nomenclature of the component somites of the three great body regions.
Limulus thus agrees with Scorpio and differs from the Crustacea, in which there are three prosthomeres - one ocular and two carrying palpiform appendages.
Again, no single point in the cortex evokes the act of ocular convergence and fixation.
An ocular segment claimed by the former division is not present or in no case demonstrable in the latter.
Here the articulation of the ocular segment is unusually distinct, and here two characters quite foreign to all the preceding groups come into view.
During the paroxysms, or even preceding them, certain sensory disturbances may be experienced, more especially affections of vision, such as ocular spectra, hemiopia, diplopia, &c. Gout, eyestrain and intestinal toxaemia have been put forward as causes of migraine, and Sir W.
In the main, the various types of minute ocular structure correspond very closely to the different groups into which mammals are divided, this correspondence affording important testimony in the favour of the general correctness of the classification.
The compound microscope generally consists of two positive lens systems, so arranged that the system nearer the object (termed the objective) projects a real enlarged image, which occupies the same place relatively to the second system (the eyepiece or ocular) as does the real object in the simple microscope.
An image is therefore projected by the ocular from the real magnified image produced by the objective with increased magnification.
THE Eyepiece Or Ocular The eyepiece is considerably simpler in its construction than the objective.
A fine scale with known intervals is put on the stage plate, and by determining the distance between the graduations of the objective micrometer formed through the same objective, by means of the screw micrometer ocular, the magnification of the objective is determined.
In the case of a suitable ocular magnification, the details will be well seen, while the aberration circles remain invisible.
It is therefore possible to judge the excellence of the focusing of objectives on the strength of the ocular-magnification, or the over-magnification, which they permit.
I, Ocular segment.
O, Ocular tubercle.
From the leaning tower of Pisa he afforded to all the professors and students of the university ocular demonstration of the falsehood of the Peripatetic dictum that heavy bodies fall with velocities proportional to their weights, and with unanswerable logic demolished all the time-honoured maxims of the schools regarding the motion of projectiles, and elemental weight or levity.
The use of atropine is absolutely contra-indicated in any case where the intra-ocular tension already is, or threatens to become, unduly high.
Abbe overcame this defect by using the so-called compensation ocular, made with Jena glasses.