Elder race - Wikipedia
But analogy may be a deceitful guide. Nevertheless all living things have much in common, in their chemical composition, their germinal vesicles, their cellular structure, and their laws of growth and reproduction.
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We see this even in so trifling a circumstance as that the same poison often similarly affects plants and animals; or that the poison secreted by the gall-fly produces monstrous growths on the wild rose or oak-tree. Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed by the Creator.
With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick; we institute poor-laws; and our medical men exert their utmost skill to save the life of every one to the last moment. There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox.
Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man himself, hardly any one is so ignorant as to allow his worst animals to breed. The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but subsequently rendered, in the manner previously indicated, more tender and more widely diffused.
Nor could we check our sympathy, even at the urging of hard reason, without deterioration in the noblest part of our nature. The surgeon may harden himself whilst performing an operation, for he knows that he is acting for the good of his patient; but if we were intentionally to neglect the weak and helpless, it could only be for a contingent benefit, with an overwhelming present evil.
We must therefore bear the undoubtedly bad effects of the weak surviving and propagating their kind; but there appears to be at least one check in steady action, namely that the weaker and inferior members of society do not marry so freely as the sound; and this check might be indefinitely increased by the weak in body or mind refraining from marriage, though this is more to be hoped for than expected. Now when naturalists observe a close agreement in numerous small details of habits, tastes and dispositions between two or more domestic races, or between nearly-allied natural forms, they use this fact as an argument that all are descended from a common progenitor who was thus endowed; and consequently that all should be classed under the same species.
The same argument may be applied with much force to the races of man. As it is improbable that the numerous and unimportant points of resemblance between the several races of man in bodily structure and mental faculties I do not here refer to similar customs should all have been independently acquired, they must have been inherited from progenitors who were thus characterised.
But I was very unwilling to give up my belief; I feel sure of this, for I can well remember often and often inventing day-dreams of old letters between distinguished Romans, and manuscripts being discovered at Pompeii or elsewhere, which confirmed in the most striking manner all that was written in the Gospels. But I found it more and more difficult, with free scope given to my imagination, to invent evidence which would suffice to convince me.
Thus disbelief crept over me at a very slow rate, but was at last complete. The rate was so slow that I felt no distress. Although I did not think much about the existence of a personal God until a considerably later period of my life, I will here give the vague conclusions to which I have been driven. The old argument from design in Nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered. We can no longer argue that, for instance, the beautiful hinge of a bivalve shell must have been made by an intelligent being, like the hinge of a door by man.
There seems to be no more design in the variability of organic beings, and in the action of natural selection, than in the course which the wind blows. But I have discussed this subject at the end of my book on the Variation of Domesticated Animals and Plants, and the argument there given has never, as far as I can see, been answered.
But I was very unwilling to give up my belief;—I feel sure of this for I can well remember often and often inventing day-dreams of old letters between distinguished Romans and manuscripts being discovered at Pompeii or elsewhere which confirmed in the most striking manner all that was written in the Gospels. The rate was so slow that I felt no distress, and have never since doubted even for a single second that my conclusion was correct. I can indeed hardly see how anyone ought to wish Christianity to be true; for if so the plain language of the text seems to show that the men who do not believe, and this would include my Father, Brother and almost all my best friends, will be everlastingly punished.
The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered. There seems to be no more design in the variability of organic beings and in the action of natural selection, than in the course which the wind blows.
Everything in nature is the result of fixed laws. Darwin's material is often misquoted. See Notable Charles Darwin misquotes. Darwin for the greater part of his book Origin of the Species [sic] has simply massed fact upon fact without any theorising, and only towards the end has formulated his conclusion which, because of the sheer weight of testimony behind it, becomes almost irresistible.
Yes I have criticised even Darwin's generalisation as being unwarranted. A few years ago I set out to canvass the literature on Charles Darwin. I do not know how many books have been written about him, but there seem to be thousands, and each year more appear. Why are there so many? Part of the answer is, of course, that he was a tremendously important figure in the history of human thought. He was an immensely likeable man, modest and humane, with a personality that continues to draw people to him even today. His comments there are among the most moving in abolitionist literature.
But it was his feelings about animals that impressed his contemporaries most vividly. Numerous anecdotes show him remonstrating with cab-drivers who whipped their horses too smartly, solicitously caring for his own animals and forbidding the discussion of vivisection in his home. At the height of his fame he wrote an article for a popular magazine condemning the infamous leg-hold trap in terms that would not seem out of place in an animal-rights magazine today.
Misattributed [ edit ] It is not the strongest of the species that survives, nor the most intelligent, but rather the one most adaptable to change. The earliest known appearance of this basic statement is a paraphrase of Darwin in the writings of Leon C. The long-term culture system LTC , originally described by Dexter for murine cells 25 and later adapted for human cells 26,27 , makes use of a rich culture medium containing high concentrations of horse serum and hydrocortisone and lower incubation temperatures, which allows the self-renewal of stem cells over a period of several months in the presence of a supportive microenvironment.
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The long-term culture of bone marrow cells employs primary adherent layers of stromal cells as an important source of cytokines and low molecular weight substances required for the controlled differentiation and proliferation of hematopoietic progenitor cells. Stromal cells provide a complex functional ECM allowing direct cell-to-cell contacts between different cell types. These, either alone or in synergy with defined cytokines, can conserve primitive stem cells, induce early differentiation of a fraction of the primitive progenitors, and prevent their terminal differentiation.
A second type of widely used LTC is the Whitlock-Witte long-term bone marrow culture 28 , initially developed for murine bone marrow to obtain stromal layers devoid of hematopoietic cells. Whitlock-Witte cultures can reconstitute the B-lymphocyte compartment in immune-compromised mice, but do not maintain primitive multilineage hematopoietic precursors such as CFU-S Sophisticated analyses such as limiting dilution analysis are used for the quantification of these cells However, even these culture systems are unable to maintain hematopoiesis indefinitely due to limiting culture conditions or, alternatively, to a natural process of senescence of the hematopoietic cells.
More recent evidence involving the transduction of CFU cells and LTC-IC using retroviral vectors, indicate that the in vitro progenitor assays currently available measure functionally different, and presumably less quiescent, populations than the long-term repopulating stem cell To obtain sustained hematopoiesis, primitive hematopoietic cells must interact with an adequate microenvironment, which includes, as already mentioned, stromal cells, ECM components and soluble regulatory factors The experimental analysis of hematopoiesis, as described above, has provided much of the present knowledge on the role played by the stroma in the process.
The term "stromal cells" is used rather loosely and the true histogeneic origin of these mesenchyme-derived cells is still uncertain. Stromal cells, which mechanically support the differentiating hematopoietic cells, include among others macrophages, fibroblasts, adipocytes, and endothelial cells and are frequently defined as non-hematopoietic cells 1, Adventitial reticular cells reside on the adluminal surface of venous endothelial cells, which branch through the medullary cavity, and appear to provide a reticular network that supports hematopoietic cells.
Marrow adipocytes possess the mechanical function of controlling hematopoietic volume: impaired hematopoiesis is associated with increased accumulation of fat inclusions, whereas accelerated hematopoiesis is associated with loss of fat vacuoles and the provision of increased space for hematopoietic cells Adipocytes may play an additional role in blood cell production as a reservoir for lipids needed in cell metabolism during proliferation. Macrophages and osteoclasts, cells derived from hematopoietic precursor cells and osteoblasts, may also play important roles in the hematopoietic microenvironment.
Macrophages are important in the clean-up of ineffective erythropoiesis and in the removal of the nuclear pole, produced during the process.
Stromal cells represent a highly dynamic structure which plays an active role in hematopoiesis by producing ECM components and both soluble and membrane-associated growth factors Stromal cells are rare in the marrow approximately 0. Although adherent stromal cell layers in LTC, established by growing bone marrow cells over a period of several weeks, are considered to mimic many characteristics of the marrow microenvironment, it has not yet been established conclusively that these cultures encompass all types of stromal cells identified in vivo and that they retain all of their functional properties in vitro.
As the heterogeneous composition of the stroma makes it extremely difficult to analyze the role of individual cell types in hematopoietic development, numerous stroma-derived cell lines have been established from bone marrow and a variety of other tissues, including spleen, thymus, and non-hematopoietic organs such as kidney, lung, skin, or mammary tumors.
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These studies have shown in vitro the heterogeneity and compartmentalization of cell types already observed during the in situ study of bone marrow. In the analysis of 33 bone marrow stromal cell lines, for instance, lineage-restricted stimulatory activity and a reciprocal relationship between granulocyte and macrophage formation were observed The cell types which compose these heterogeneous populations are also being separately analyzed. In one study, three cell types could be grown separately in vitro , and were identified as macrophages, endothelial-like cells and myofibroblasts, with different potential for the support of hematopoietic cell growth Hematopoietic stromal precursors have been described, besides adult bone marrow, in fetal liver and fetal bone marrow, with reported differences in the anatomic and ultrastructural characteristics which, however, have not been clearly correlated to functional differences 6,41, Several studies suggest that hematopoietic progenitors collected at one stage of ontogenetic development may not be able to interact with a microenvironment originating from cells at a different ontogenetic stage.
The observation that fetal liver progenitors may not be capable of differentiating in an adult bone marrow microenvironment, for instance 43 , may have important implications for fetal liver transplantation into postnatal recipients. The ontogeny of stromal cells is currently very poorly understood. Based on the well-established generation of multiple mesenchymal cell types from bone marrow cells, the existence of stromal stem cells has been proposed Besides gaps in our knowledge of the biology of these cell populations, much information at the molecular level is also lacking.
At least 16 Hox genes and 5 genes with homeobox domains have already been identified, although their temporal expression has not yet been determined The transplantation capability of stromal cells is also a controversial subject. In an in vivo system, it has been reported that murine bone marrow mesenchymal precursor cells, expanded in culture, were detected in the bone, cartilage and lungs of recipient mice at 1 to 5 months after transplantation Recently, the migration of bone marrow-derived cells to areas of induced muscular degeneration, followed by differentiation along the myogenic pathway and participation in the regeneration of damaged fibers, has been reported in mice Differently from hematopoietic cells, the existence of stromal precursors outside the bone marrow in adults is highly controversial, so that while some studies have detected their presence in peripheral blood , others have reported negative results 56, The existence of stromal precursors in cord blood under normal conditions is the subject of intense discussion A representative recent study 58 , for instance, reports deficient myeloid progenitor cell growth in LTC of umbilical cord blood, suggesting that this is due to the impaired development of an adherent layer.