The Microscope and Its Revelations, Volumes 1-2 |
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Common terms and phrases
achromatic acid adjustment angle angular aperture animal animalcules aperture apochromatic appearance arrangement attached axis balsam binocular body calcareous Canada balsam canal cavity cells centre chambers cilia colour condenser cone conjugation cover cover-glass diameter diaphragm diatoms diffraction disc edge elongated employed endochrome extremely eye-piece filaments flagella flagellum fluid focal focus Foraminifera frustules glass illumination imbedded inch Infusoria instrument Journ larvæ layer lens lenses light magnifying power membrane micro microscope microscopist microtome milled head minute mounted movement nose-piece nucleus numerical aperture object object-glass oblique observed obtained optical ordinary organs particles pencil plane plants plate portion present prism Professor protoplasm rays refractive refractive index screw seen segments shell shown in fig side slide sometimes species specimens spherical spherical aberration spores stage staining stem structure sub-stage substance surface thickness thin tion tissue tube valves Volvox whilst zoospores zygospore
Popular passages
Page 733 - Suppose a human mason to be put down by the side of a pile of stones of various shapes and sizes, and to be told to build a dome of these, smooth on both surfaces, without using more than the least possible quantity of a very tenacious, but very costly, cement, in holding the stones together. If he accomplished this 42 well, he would receive credit for great intelligence and skill. Yet this is exactly what these little 'jelly specks...
Page 526 - ... preserved by Saxo. But to the origin of the rest the genealogies give us no clue. If they were all of royal origin — and apparently they did claim divine descent — the Angli must have possessed a numerous royal class ; and we are scarcely justified in denying that this may have been the case1. On the other hand it is by no means impossible that some of them were sprung from foreign peoples, such as the Danes, Swedes or Warni. But what we may regard as practically certain is that the individual...
Page 914 - ... or true proboscis, which contains a tube for suction. Feet. — These organs vary with the habits of life in different species. The limb consists of five divisions: the coxa or hip, the trochanter, the femur or thigh, the tibia or shank, and the tarsus or foot. This last has usually five joints, but sometimes less. The Coleoptera are subdivided into groups, according as the tarsus consists of five, four, or three segments. The last joint is furnished with hooks or claws, and in the fly, etc.,...
Page 325 - ... of the field and the variation produced by using alternately central and very oblique illumination. When the objective is perfectly corrected for spherical aberration for the particular thickness of cover-glass under examination, the...
Page 301 - If the radiant is now made to approach the glass, so that the course of the ray, fde g, shall be more divergent from the axis, as the angles of incidence and emergence become more nearly equal to each other, the spherical aberration produced by the two will be found to bear a less proportion to the opposing error of the single correcting curve acb ; for such a focus, therefore, the rays will be over-corrected.
Page 525 - is not avoided but pushed aside ; or, if it be sufficient to avert the onward course of the frustule, the latter is detained for a time equal to that which it would have occupied in its forward projection, and then retires from the impediment as if it had accomplished its full course.
Page 325 - Nebulous doubling with oblique illumination indicates over-correction of the marginal zone ; indistinctness of the edges without marked nebulosity indicates under-correction of this zone ; an alteration of the focus for oblique and central illumination (that is, a difference of plane between the image in the peripheral and central portions of the objective) points to an absence of concurrent action of the separate zones, which may be due to either an average underor over-correction, or to irregularity...
Page 543 - The northern seas are frequently coloured, over patches of hundreds of square miles, of a dark deep green, by the myriads of these minute plants. Dr. Hooker says that the universal presence of this invisible vegetation throughout the South Polar Ocean is a most important feature, since there is a marked deficiency in this region of higher forms of vegetation, and were it not for them there would neither be food for aquatic animals, nor could the ocean water be purified of the poisonous carbonic acid...
Page 321 - ... extent of amplification rather than by clearness of outline. So that an observer is tempted to affirm that he can discern through his pet lens what no eye can see or lens show. This happens chiefly with the inexperienced beginner, but not unfrequently also with the advocate of extremely high powers, in whose mind separation of detail means analysis of structure, and optically void interspaces prove the non-existence of anything which he does not see. As much time is often lost by frequent repetition...
Page 911 - ... place it in strong acetic acid : this will soften or decompose all the viscera, and the tracheae may then be well washed with the syringe, and removed from the body with the greatest facility, by cutting away the connections of the main tubes with the spiracles by means of the fine-pointed scissors.