Microscopical Researches Into the Accordance in the Structure and Growth of Animals and Plants

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Sydenham Society, 1847 - 268 páginas
 

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Página 163 - He comes to the conclusion that "the elementary parts of all tissues are formed of cells in an analogous, though very diversified manner, so that it may be asserted that there is one universal principle of development for the elementary parts of organisms, however different, and that this principle is the formation of cells.
Página 187 - But in animated nature, adaptation—individual adaptation— to a purpose is so prominently marked, that it is difficult to reject all teleological explanations. Meanwhile it must be remembered that those explanations, which explain at once all and nothing, can be but the last resources, when no other view can possibly be adopted; and there is no such necessity for admitting the teleological view in the case of organized bodies. The adaptation to a purpose which is characteristic of organized bodies...
Página 163 - ... a structureless substance is present in the first instance, which lies either around or in the interior of cells already existing; and cells are formed in it in accordance with certain laws, which cells become developed in various ways into the elementary parts of organisms.
Página 195 - ... layer is attracted: for the nucleolus, the nucleus and cell-membrane are composed of materials which differ in their chemical properties. Such are the peculiarities of the plastic power of the cells, so far as they can as yet be drawn from observation. But the manifestations of this power presuppose another faculty of the cells. The cytoblastema, in which the cells are formed, contains the elements of the materials of which the cell is composed, but in other combinations : it is not a mere solution...
Página 213 - ... themselves are essentially the same. The view then that organisms are nothing but the form under which substances capable of imbibition crystallize, appears to be compatible with the most important phenomena of organic life, and may be so far admitted, that it is a possible hypothesis ; or attempt towards an explanation of these phenomena. It involves very much that is uncertain and paradoxical, but I have developed it in detail, because it may serve as a guide for new investigations. For even...
Página 189 - It is, however, unnecessary to do so, because an explanation, according to the teleological view, is only admissible when the physical can be shown to be impossible. In any case it conduces much more to the object of science to strive, at least, to adopt the physical explanation. And I would repeat that, when speaking of a physical explanation of organic phenomena, it is not necessary to understand an explanation by known physical powers, such, for instance, as that universal refuge electricity,...
Página 186 - In physics, all those explanations which were suggested by a teleological view of nature, as "horror vacui," and the like, have long been discarded. But in animated nature, adaptation — individual adaptation — to a purpose is so prominently marked, that it is difficult to reject all teleological explanations. Meanwhile it must be remembered that those explanations, which explain at once all and nothing, can be but the last resources, when no other view can possibly be adopted; and there is no...
Página 161 - ... and the uniform principle of development in vegetable cells might be explained by the slight physiological difference of their elementary particles. The object, then, of the present investigation was to show, that the mode in which the molecules composing the elementary particles of organisms are combined does not vary according to the physiological signification of those particles, but that they are everywhere arranged according to the same laws; so that whether a muscular fibre, a nerve-tube,...
Página 39 - When this takes place, the nucleus usually appears to be formed first, and then the cell around it. The formation of cells bears the same relation to organic nature that crystallization does to inorganic. The cell, when once formed, continues to grow by its own individual powers, but is, at the same time, directed by the influence of the entire organism in such manner as the design of the whole requires. This is the fundamental phenomenon of all animal and vegetable vegetation. It is alike equally...
Página v - ... matter deposited around them formed the mass of the ganglionic globules, which were thus developed. Valentin has also observed, that after the development of nervous fibres, nuclei, elongated fibre cells, and fully developed fibres of cellular tissue are formed around them. *] Schwann's discoveries are to be ranked amongst the most important steps by which the science of physiology has ever been advanced.

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