162 QUARTERLY CHRONICLE. 
individually as animated beings; for there are numberless 
animals belonging to the order infusoria which consist of a 
single cell. Such an animal, for instance, is an Amoeba, a 
minute, microscopic, protoplasmic mass, with nucleus and 
nucleolus. If its actions are observed under the microscope, 
one can see how it alters the form of its body at will ; how it 
sends forward prolongations here and there, draws out the 
mass of its body, and so changes its place. On outward 
irritation it generally rolls itself up into a bullet-shaped 
lump, and rapidly draws in again all the prolongations lately 
stretched forward. Often one may observe it engulf smaller 
bodies in its substance, where they are changed—one may 
say, digested—and half disappear, the undigested leavings 
being again ejected. The little animal grows, and goes on 
propagating itself by division. 
« A cell which belongs to the tissues of one of the higher 
animals behaves exactly in the same manner asa single-celled 
infusorium. For example, in the blood we have cells; the 
so-called white blood-corpuscles, which are exactly like certain 
infusoria. Thus, they stretch out prolongattons of their sub- 
stance subject to their will, and upon irritation and the like 
they show the well-known reactions. The cells in connective 
tissue deport themselves similarly, They crawl regularly 
about in certain chasms in the substance of the tissue 
formed beforehand, which they elaborate 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 phenomena 
described. These facts are truly among the most beautiful 
acquisitions to our knowledge lately derived from micro- 
scopic research. They had for a long time escaped the 
attention of microscopic 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 organized 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 being—movement at will, and reaction on 
outward irritation. Thus, then, we can by a well-connected 
chain of strict analogies arrive at the proposition which was 
placed before us. Each cell, whether it be an independent 
