A Criticism of the Cell-Theory; being an Answer to Mr. Sedgwick's ...

A CRITICISM OF THE CELL-THEORY. 149
welche der Anatom die pflanzlichen und thierischen Organismen
zerlegt, sind die Trager der Lebensfunctionen, sie sind,
wie Virchow sich ausgedriickt hat die 'Lebenseinheiten.'
Von diesem Gesichtspunkt aus betrachtet, erscheint der
Gesammtlebensprocess eines zusammengesetzten Organismus
nichts Anderes zu sein als das hochst verwickelte Resultat
der einzelnen Lebensprocesse seiner zahlreichen, verschieden
functionirenden Zellen." The whole book is written "von
diesem Gesichtspunkt aus," and, admirable as it is, there is
reason to think that its value is somewhat impaired by the
excessive value attributed to the cell as an independent vital
unit.
In passing, I may remark that this passage of 0. Hertwig's
gives a very precise and definite statement of the cell theory,
as it is held now, by a very great authority; and a reference
to older works would have shown Mr. Sedgwick that, so stated,
it is practically the same as what its authors stated. 1
For the original words of Schwann are these: " 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 In inferior
plants any given cell may be separated from the plant and can
grow alone. So that here are whole plants consisting of cells
which can be positively proved to have independent vitality.
Now, as all cells grow according to the same laws, and consequently
the cause of growth cannot in one case lie in the cell
and in another in the whole organism, and since it may be
further proved that some cells, which do not differ from the
rest in their mode of growth, are developed independently,
we must ascribe to all cells an 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. The cause of nutrition and growth
1 ''lam not concerned with what its authors held."—Mr. Sedgwick, op. cit.,
p. 88.