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book reviews

NATURE CELL BIOLOGY VOL2 AUGUST 2000 www.nature.com/ncb E149

Deciphering the structureof living beings

The imaginative power of nature cer-tainly could not have produced any-thing more flexible than the cell to

account for every complex morphology ofthe organic world. In the same way that theseven notes of the scale generate all possi-ble musical composition, cells embeddedand linked together produce the strangefractal living shapes we see everywhere. Itwas not easy, however, to reach this unitaryconcept of life and in fact it took more thantwo hundred years after the microscopehad been invented at the beginning of theseventeenth century.

In The Birth of the Cell, Henry Harris,Regius Professor Emeritus of Medicine atthe University of Oxford, narrates the his-tory of the extraordinary intellectualadventure that led us to consider the cellsas the basic bricks of living organisms.Digging into the many scientific, historicaland philosophical intricacies of the subject,and going back to the primary sources withthe relevant passage often translated for thefirst time in English (but reported in theoriginal language in the useful appendix),Harris vividly portrays an exciting historyof discoveries, theoretical synthesis andtransmission of ideas, but also of falseways, misinterpretations of experimentaldata, personal idiosyncrasies, nationalpride, and political and social frictionamong scientists throughout Europe. Onthe whole, Harris’s book is very informa-tive and it amends a lot of errors and mis-conceptions of the previous assessment ofthe early history of cytology and histology.By the end the reader will have acquired anextremely detailed idea of the origin ofevery fundamental contribution in the con-ceptual edifice of cell theory.

The history of cell theory, as properlydepicted by Harris, is the history of twofundamental themes that emerge through-out the book. The first is the homologybetween unicellular and multicellularorganisms and the second is the structuralhomology between plants and animals.

Unicellular organisms, in which life

could be imagined on the basis of theirmotility, were discovered in the seventeenthcentury by the Dutch microscopist Antonivan Leeuwenhoek. These ‘little animals’were subsequently seen in vegetable andanimal infusions and for this reason named‘infusoria’. It was more difficult to reducethe multicellular organisms to their basicelements, although the English physicistRobert Hooke discovered single cells in theliving plant as long ago as 1665, when hediscovered, in thin sections of cork, micro-scopic cavities enclosed in a tridimensionalnet of walls. Given their analogy with cubi-cules or small rooms, the Latin for which iscella, Hooke applied the term cell to theseempty spaces. It remained in literature andeventually became the eponym to indicatethe basic unit of life, even if Hooke used theword differently to later biologists (hethought of the cork cells as passages for‘natural juices’ of the plant). Harris pointsout that it was not until 1805 that the biol-ogist Lorenz Oken had the prescient intui-tion of the fundamental homology betweenthe ‘little animals’ of Leeuwenhoek and themulticellular organisms (such as the corkstudied by Hooke) according to whichaggregates of cooperating ‘infusoria’become living tissue. But, as Harrisobserves, this extraordinarily propheticvision remained uninfluential because itwas far too early for the scientific commu-nity of the time, and it was more than thir-ty years before it became common amongbiologists.

That plants and animals are homolo-gous in structure was similarly difficult tograsp, and appreciation of this fact was nota sudden and single acquisition but theresult of decades of scientific endeavour.Harris gives a systematic evaluation of thecontributions of biologists such asPurkinje, Valentin, Rusconi and Dumortier,whose studies, in the context of cell theory,are not generally fully recognized in stan-dard textbooks. A substantial revision hasbeen made by Harris in considering thedramatic generalization of cell theory

(1838-9) to which the names of Schwannand Schleiden remained attached. Thesebiologists generalized the concept thatplants and animals are composed of cellswith a similar nucleus and nucleolus, andthat the process of formation of cells is thebasis of the development of organisms.However, their theory was wrong from aphysiological point of view, as they thoughtthe new cells develop by a sort of ‘crystal-lization’ around a nucleus, with progressiveenlargement of this ‘condensed’ material.

Harris’s hero is clearly Robert Remak(another scientist not acknowledged in hislifetime nor adequately recognized evennow, as Harris points out) who disprovedthe theory of Schwann and Schleiden anddemonstrated that new cells aris by aprocess of binary scission from pre-existingcells. In the second half of the nineteenthcentury the cell theory (or cell doctrine asHarris calls it in the last paragraph of thebook) reached its definitive form. It was atthis time that the prophetic intuition ofGoethe – “every living being is not a singlebut a plurality; even if it presents itself as anindividual it remains however a whole ofautonomous and living beings” (Die AbsichtEingeleitet, 1807) – found its definitive con-firmation.Paolo Mazzarello is in the Istituto diGenetica Biochimica ed Evoluzionistica,CNR , 27100 Pavia, Italye-mail: mazzarello@igbe.pv.cnr.it

The Birth of the Cell by Henry Harris

Yale University Press,New Haven and London 1999

First published in paperback May 2000.£11.95, $17

Paolo Mazzarello

…By the end the reader

will have acquired an extremely

detailed idea of the origin of

every fundamental contribution

in the conceptual edifice of

cell theory…