240 On Cell Life. [April, 
in connective tissue deport themselves similarly. They crawl regu- 
larly about in certain chasms in the substance of the tissue formed 
beforehand, which they elaborated for themselves, which, in fact, they 
have constructed as their dwelling. What is particularly worthy of 
attention is, that these cells when they have left the tissue, can 
move themselves for some time in a fluid, and show all the pheno- 
mena described. These facts are truly among the most beautiful 
acquisitions to our knowledge lately derived from microscopic 
research. They had for a long time escaped the attention of micro- 
scopic observers, because animal tissues were not examined under 
the same condition in which they exist in the living organism. It 
has already been mentioned that cells in the tissues of highly organ- 
ized animals are exactly the same in their growth and reproduction 
as single-celled organisms. And, in the last place, to complete the 
identity, all the cells of a whole animal are actually the brood — 
of one single cell—namely, the ovum. We have here before us 
exactly the phenomena which we regard as the characteristics of an 
animated beng—movement at will, and reaction on outward irrita- 
tion. ‘Thus, then, we can by a well-connected chain of strict analogies 
arrive at the proposition which was placed before us. Hach cell, 
whether it be an independent animal or part of the tissues of a 
higher organism, is in itself, subjectively, an animated being. ‘The 
want of self-dependence in the cell, which forms a part of the tissues 
of a higher animal, is really not greater than in the single-celled 
infusorium, which lives freely by itself. In fact, each organism 
has its own conditions of life; and as the tissue-cells can only live, 
for any length of time, in a certain fluid, or in their appointed self- 
wrought habitation, where they dwell as a compound organism, so 
can certain single-celled infusoria live persistently only in certain 
fluids; they also die if placed under conditions to which their 
organization is not adapted. I am not, moreover, at all certain, as 
before said, of the impossibility of a cell, if once removed from the 
blood or connective tissue of a higher animal and placed in another 
soil (as it were) under favourable auspices, proceeding with its life 
as an independent animal, and becoming the mother of a brood of 
infusoria. 
From the standing-point which we have now gained, we cannot 
call an organism which consists of more than one cell an individual. 
Such an object is much more like an association of individuals, which 
live together in a habitation wrought by them. ‘The cells have 
themselves secreted the materials for building from their bodies. 
Association makes a division of labour possible. It is no longer 
necessary for each cell to execute for itself every organic function— 
digestion, assimilation, &c., in their different stages. One group is 
able much more satisfactorily to execute this, and another that 
office for the whole household; and thus the particular functions 
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