SECTION III. 
REVIEW OF THE PREVIOUS RESEARCHES—THE FORMATIVE 
PROCESS OF CELLS——THE CELL THEORY. 
Tue two foregomg sections of this work have been devoted 
to a detailed investigation of the formation of the different 
tissues from cells, to the mode in which these cells are de- 
veloped, and to a comparison of the different cells with one 
another. We must now lay aside detail, take a more ex- 
tended view of these researches, and grasp the subject in its 
more intimate relations. The principal object of our investi- 
gation was to prove the accordance of the elementary parts of 
animals with the cells of plants. But the expression “ plant- 
like life” (pflanzen-ahnliches Leben) is so ambiguous that 
it is received as almost synonymous with growth without 
vessels; and it was, therefore, explained at page 6 that in 
order to prove this accordance, the elementary particles of 
animals and plants must be shown to be products of the same 
formative powers, because the phenomena attending their deve- 
lopment are similar ; that all elementary particles of animals 
and plants are formed upon a common principle. Having 
traced the formation of the separate tissues, we can more 
readily comprehend the object to be attained by this compa- 
rison of the different elementary particles with one another, a 
subject on which we must dwell a httle, not only because it is 
the fundamental idea of these researches, but because all 
physiological deductions depend upon a correct apprehension 
of this principle, 
When organic nature, animals and plants, is regarded as a 
Whole, in contradistinction to the inorganic kingdom, we do 
not find that all organisms and all their separate organs are 
compact masses, but that they are composed of innumerable 
small particles of a definite form. These elementary particles, 
however, are subject to the most extraordinary diversity of 
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