A QRITICISM OF THE CELL-THEORY. 149 
welche der Anatom die pflanzlichen und thierischen Organis- 
men zerlegt, sind die Triger 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 héchst 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 O. Hertwig’s 
gives a very precise and definite statement of the cell theory, 
as it is held now, bya 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.! 
For the original words of Schwann are these: “ The ele- 
mentary parts of all tissues are formed of cells in an analo- 
gous 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 conse- 
quently 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 uf 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 “Tam not concerned with what its authors held.”—Mr. Sedgwick, op. cit., 
p. 88. 
