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    1074 THE L E A PER. [Saturday,

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    Huxley On The Cell-Theory. The British A...

    Such a doctrine is , in fact , a moat obvious and almost a necessary development of the doctrine of epigenesis in general . " To one who had worked out the conclusion , that the most complex , grosser , animal or vegetable organizations , arise from a semi-fluid and homogeneous mass , by the continual and successive establishment of differences in it , it would be only natural to suppose that the method of nature , in that finer organization which We call histological , was the same ; and that as the organ is developed by the differentiation of cells , so the cells are the result of the differentiation of inorganic matter . If the organism be not constituted by the coalescence of its organs and tissues in consequence of their p eculiar forces , h ut if , on the other hand , the organism exists before its organs and tissuss , and evolves them , from itself , —is it not probable that the organs and tissues also , are not produced by the coalescence of the cells of which they are composed , in consequence of their peculiar forces , but , contrariwise , that the cells are a product of the differentiation of something which existed before them ?

    " For Schwann the organism is a beehive , its actions and forces resulting from the separate but harmonious action of all its parts ( compare Schwann , 1 . c ., p . 229 ) . For Wolff it is a mosaic , every portion of which expresses only the conditions under which the formative power acted , and the tendencies by which it was guided . " Here , while upholding the doctrine of Epigenisis , he expresses that of Evolution , for he conceives the organism to exist before its organs , and to evolve them from itself ! What is that but the doctrine of pre-existent germs evolving into organisms ? Then again , he asks whether the cells are not products of the differentiation of " something" which existed before them . Assuredly . Schwann would be equally emphatic in maintaining such a position ; but he would add the " something" is not an organism , because an organism is the sum total of its organs . There are other indications of a metaphysical tendency , but we pass on to the criticism of the cell-theory .

    Mr . Huxley undertakes to establish the error of these three fundamental positions assumed by Schleiden and Schwann : — " 1 . The prevalent notion of the anatomical independence of the vegetable cell , considered as a separate entity . " 2 . The prevalent conception of the structure of the vegetable cell . " 3 . The doctrine of the mode of its development . " His remarks on the first count are , in our opinion , to be rejected as

    inconclusive , and opposed by tho strongest evidence . The vegetable cell is independent , and dependent also ; just as human beings are independent , yet considered as parts of the social organism they are mutually dependent . A cell may live isolated , or in aggregation with others , just as a man may . And the biological series displays immense varieties in the gradation of dependence , so that in the complex organisms the individual cell has lost its power of independence merged in a dependence on a higher life . Schwann ' s remarks on this point are so good , that the reader will thank us , if we take the volume from our shelves and quote them : —

    "We have seen that all organized bodies are composed of essentially similar parts , namely , of cells ; that these cells are formed and grow in accordance with essentially similar laws ; and , therefore , that those proce ? fies must , in every instance , be produced by the same powers . Now , if we find that some of these elementary parta , not differing from the others are capable of separating themselves from tho organism , and pursuing an independent growth , we may thence conclude that each of the other elementary parts , each cull , is already possessed of power-to take up fresh molecules and grow ; and that , therefore , every elementary part possesses a power _ of its own , an independent life , by means of which it would 1 ) 0 enabled to develop itself independently , if the relations which itboro to external parts were but similar to these in which it stands in tho organism . Tho ova of animals afford uh examples of such independent cells , growing apart from the

    organism . It may , indeed , be said of the ova of higher animals , that after impregnation the ovum is essentially different from i \ w . other cells of the organism ; that by impregnation there in a . something conveyed to the ovum , which is more to it than an external condition for vitality , more than nutrient matter ; and that it might thereby have first received its peculiar vitality , and therefore that nothingcan be inferred from it with respect to the other cells . But this fails in applie . v tion to those classes which consist only of female individuals , as well as with the spores of the lower plants ; and , besides , in the inferior plants any c / iven cell may be separated from the plant , and t / tmyrow alone . , SO that here are whole plants contesting of cells , which can be positively proved to liavo independent vitality Now , an all cells grow according to the . same laws , and eo : i . seqmently the oau . se of cannot he in tho cell

    growth m one ease , and in another in tho whole organismmid since it may be further proved that some cells , which do not differ from tho rest in their mode of growth , are developed independently , we must ascribe to all cells : ui independent vitality , that is , such combinations of molecules as occur in any single cell , are capable of setting free the power by which it is enabled to take up fresh molecules . . L lie causeol nutrition and growth resides not in the organism as a whole , but in tho separate elementary parts -the cells . The failure of growth in the case of any particular cell , when . separated from a , n organized body is as slight an objection to tins theory , as it is an objection against the independent vitality of a bee , that it cannot continue long in existence after being aeparated from its . swarm . The manifestation of the power which resides in the cell depends upon conditions to which it is subject only when in connexion with the whole ( organism ) . "

    The Hccond and third counts , namely , respecting ( h <> Hfcnu-iuro anil dovelopinenf ; of tho vegetable cell , Mr . Huxley proven with siiccen . s The discovery ol '\ hc primordial utricle by Hugo von Mohl necessaril y altered the aspect of tho whole < juoNtion . ftrhwmm , however , knew of Mm existence of cells without nuclei , and regarded the- nucleus mm a , primary cell ¦ and we will here rrive hia explanation : — '

    "The fact that many nuclei are developed into hollow vesicles , and tho difficulty Of distinguishing noine of these- hollow nuclei from c < ;]] H > forms quite Huflioient ground for the supposition that a nucleus does not did ; ,,- essentially from a , cell ; that an ordinary nucleated cell is nothing more than a cell formed around the outside of another cell , tho nucleus ; and than the only dili ' orcnce between 1 , 1 k ; two consists in the inner one being more slowly and less completel y developed , after tho external one has been formed around it . If thin description were correct we might express ourselves with more precision , atid < Ie . sigiui . to the nuclei as oells of the first order , and the ordinary nucleated cells as cells of the second onlor llil . herto wo have decidedly maintained a distinction between cell and nucleus " ; uid it was convenient to do so as long as we wort . ) engaged in merel y de . scribinir tho observations . Then ) can bo no doubt , that the nuclei correspond | ,, ( OIU , another in , all cells ; but ( ho designation , ' cells of the firnl- order , ' includoH Jt theoretical viow'of tho matter which has yet to be proved , namely , the identity of

    the formative process of the cell and the nucleus . This identity , however , is of the greatest importance for our theory , and we must therefore compare the two processes somewhat more closely . The formation of the cell commenced with the deposition of a precipitate around the nucleus ; the same occurs in the formation of the nucleus around the nucleolus . The deposit becomes denned externally into a . solid stratum : the same takes place in the formation of the nucleus . : The development proceeds no farther in many nuclei , and we also meet with cells which remain stationary at the same point . The further development of the cells is manifested either by the entire stratum , or only the external part of it becoming consolidated into a membrane ; this is precisely what occurs with the nuclei which undergo further increases in its

    development . The cell-membrane superficies , and often in thickness also , and separates from the nucleus , which remains lying- on the wall- the membrane of the hollow cell-nuclei grows in the same manner , and the nucleolus remains adherent to a spot upon the wall . A transformation of the ceU-contents frequently follows , giving rise to a formation of new products in the cell-cavity . In most of the hollow cell-nuclei , the contents become paler , less granulous and in some of them fat-globules , & c , are formed . We may therefore say that the formation of cells is but '; i . repetition around the nucleus of the same process by which the nucleus was formed around the nucleolus , the only difference being that the process is more intense and complete in the formation of cells than in that of nuclei . "

    After reading this passage we can accept what Mr . Huxley says , without its greatly altering Sen warm ' s theory : — " Since , then , the functions of the vegetable ' cell * can be effectually carried on by the primordial utricle alone ; since the ' nucleus' has precisely the same chemical composition as the primordial utricle ; and since , in some cases of celldivision , new nuclei are seen to arise in the substance of the endoplast , by a mere process of chemical and morphological differentiation ( "Von Moil , 1 . c , p . 52 ) it follows , we think , that the primordial utricle must be regarded as the essential part of the endoplast— -the protoplasm and nucleus being simply its subordinate and , we had almost said , accidental anatomical modifications . " We cannot enter further into details , but refer to Mr . Huxley ' s paper , and conclude these observations with an extract or two from his speculative passages : — WHAT AEE CELLS ?

    " ¦ "What is the meaning of the unquestionable fact , that the first indication of vitality , in the higher organisms at any rate , . is the assumption of the cellular structure ? " In answering these questions , we would first draw attention to the definition of the nature of development in general , first clearly enunciated by "Von Baer . ' The history of development , ' he says , 'is the history of a graduall y increasing differentiation of that which was at first homogeneous . ' The yelk is homogeneous ; the blastoderma is a portion of it which becomes different from the rest , as the result of the operation of the laws of growth ; the blastoderma , again ,

    comparatively homogeneous , becomes differentiated into two or more layers ; the layers , originally identical throughout , set up different actions in their vari ous parts , and are differentiated into dorsal and visceral plates , chorda xlorsalis and bodies ofvertebras , & o . & c . No one , however , imagines that there is any causal connexion between these successive morphological states . No one has dreamt of explaining the development of the dorsal and visceral plates by blastodermic force , nor that of the vertebrce by chorda-dorsnTie force . On the other hand , all theso states are considered , and justly , to result from the operation of some common determining power , apart from them all—to be , in facfc , the modes of manifestation of that

    power . "Now , why should we not extend this view to histology , which , as we have explained , is only ultimate morphology ? As the whole animal is the result of the differentiation of a structureless yelk , . so is crery tissue the result of the differentiation of a structureless blastema —the first step in that differentiation beiny the separation of the blastema into endoplast , and ycr iptast , or the formation of what is called a ' nucleated cell : Then , just as in the development of the embryo , when the blastoderm ic membrane is once formed , new organs are not developed in other parts of the yelk , but proceed wholly from the differentiation of the blastoderm , — so historically , the ' nucleated cell , ' the poriplast with its endoplaat , onco formed , further development takes place by their growth and differentiation into new

    cndoplasts and peripla :- » ts . Tlie further change into a special tissuo , of course , succeeds and results from thin primary differentiation , as we have soen the bodies of the vertebras succeed the chorda dorsalis ; but is there any moro reason for supposing a causal connexion between the one pair of phenomena , than between tho other ? The cellular structure precedes the special structure ; but is the latter , therefore , the result of a ' cell-force , ' of whose existence thcro m on other grounds no evidence whatever . We must answer in the negative . For uh the primarily cellular structure of plants and animals is simply a fact in the history of their hintological development—a histologically necessary stage , if ono may so call it , which has no more cau « al connexion with that which follows it , than tho equally puzzling morphological necessity for the existence of a chorda dorsalis or of Wolffian bodies has , with the development of the true vertebras or of tho true kidneys . "

    We bog to add , in passing , that thcro isn , causal connexion between ( he chorda dorsnlifl and tho ver (; ebra \ tho Wol / lian bodies and tho kidneys . ( Tho ro . iHon is given in Comics ' . PMlosopliy of the Sciences , p . 3 < L ) TH . K HTHlTcrUKK OF VLANTH AND ANIMALS . "Vitality , the faculty , ( hat is , of exhibiting definite cycles of change in form and composition , is a property inherent in certain kinds of matter . "Thcro is a condition of all kinds of living matter in which it is an amorphous germ that is , in which its external form depends merely on ordinary physical laws , and in which it possesses no internal structure . "Now , according to the nature of certain previous conditionti - -the character of tho changes undergone --of the different states necessarily oxliibitod—or , in other words , 1 . 110 successive differentiations of the amorphous muss will bo di Heron t .

    " Conceived as a , whole , from their commencement to their termination , they constitute the individuality of the living being , and tho passage of the living being through these states , is called its development . Development , therefore , and lift ) are , strictly speaking , one thing , though we tiro accustomed to limit the former to tho progressive half of lifo merely , and to speak of the iotrogz'oflsivo half an decay , considering an imaginary renting point between the two aH tho adult or perfect til-ate . "The individuality of a living thing , then , or a single lifo , in a continuoufi development , and development in the continual differentiation , tho constant cyclical change of that ; which was , at iin < | , , morphologically and chemically imliHorout and homogeneous .

    "The morphological differentiation may bo of two kinds . In tho lowest animals and plants the so-called unicellular organisms it . may ho said t <> bo external , tho changes of form being essentially confined to tho " outward hImij )" of tho germ , and being unaccompanied by tho development of any intonialHtru cturo .

    1074 The L E A Per. [Saturday,

    1074 THE L E A PER . [ Saturday ,

• Citation
  • Leader (1850-1860), Nov. 5, 1853, page 18, in the Nineteenth-Century Serials Edition (2008; 2018) ncse-os.kdl.kcl.ac.uk/periodicals/l/issues/cld_05111853/page/18/