2 INTRODUCTION. 
Wien, 1838, p. 14,) they in like manner consist of cells, the 
partition-walls of which become obliterated. 
Animals, which present a much greater variety of external 
form than is found in the vegetable kingdom, exhibit also, and 
especially the higher classes in the perfectly-developed condition, 
a much more complex structure in their individual tissues. 
How broad is the distinction between a muscle and a nerve, 
between the latter and cellular tissue, (which agrees only in 
name with that of plants,) or elastic or horny tissue, and so 
on. When, however, we turn to the history of the development 
of these tissues, it appears, that all their manifold forms originate 
likewise only from cells, indeed from cells which are entirely 
analogous to those of vegetables, and which exhibit the most 
remarkable accordance with them in some of the vital pheno- 
mena which they manifest. The design of the present treatise 
is to prove this by a series of observations, 
It is, however, necessary to give some account of the vital 
phenomena of vegetable cells. Each cell is, within certain 
limits, an Individual, an independent Whole. ‘The vital phe- 
nomena of one are repeated, entirely or in part, in all the rest. 
These Individuals, however, are not ranged side by side as a 
mere Aggregate, but so operate together, in a manner unknown 
to us, as to produce an harmonious Whole. The processes 
which go forward in the vegetable cells, may be reduced to the 
following heads: 1, the production of new cells; 2, the expan- 
sion of existing cells; 8, the transformation of the cell-contents, 
and the thickening of the cell-wall; 4, the secretion and ab- 
sorption carried on by cells. 
The excellent researches of Schleiden, which throw so much 
light upon this subject, form the principal basis for my more 
minute observations on these separate vital phenomena. (See his 
“ Beitrage zur Phytogenesis,” in Miuller’s Archiv, 1838, p. 137, 
plates 3 and 4.)1 
First, of the production of new cells. According to Schleiden, 
in Phenogamous plants, this process always (except as regards 
the cells of the Cambium,) takes place within the already ma- 
ture cells, and in a most remarkable manner from out of the 
well-known cell-nucleus. On account of the importance of the 
1 [A translation of this paper forms part of this volume.—Trawns. ] 
