146
E . N . W I L L M E R
other hand, more vigorous cell movement immediately begins and the
extent and character of this movement (which is considered in detail
in Chapter 5) depends upon four things, at least. The age of the tissue,
the nature of the tissue, the nature of the substrate upon which the
movement takes place and the nature of the medium surrounding the
tissue are all of importance.
In using hanging-drop and slide-chamber cultures as a way of examining and studying cells, it is always helpful, and often essential for
diagnostic purposes, to make full use of micro-cinematographic
recording (see p. 40), in order to study cell movement. Single observations on cultures, or fixed and stained preparations of cultures
(see Fig. 1), are relatively useless for many of the problems that arise
in classifying cells which are constantly moving and changing. T w o men
standing on a hill-side may appear almost identical when seen from
a distance or in a still photograph; but as soon as they move or when a
cine-film of their movement is viewed, one, perhaps an insurance agent,
can be identified by his quick short step, and the other will be easily
recognized as the hill farmer by his long and loping stride. So it is with
cells. A macrophage emerging from an explant and creeping out between
a plasma clot and a glass surface sends out rounded pseudopodia,
lamelliform membranes or pseudopodia with "ruffles", and it moves
first this way and then that. An adjacent fibroblast, on the other hand,
glides outwards with what appears to be a more purposeful and directionally constant motion with only the leading edge frayed into ruffles.
As soon as it is possible to see and appreciate these movements, therefore, the distinction between the two classes of cell may become much
more obvious.
This does not, of course, mean that it is always possible even with the
help of the cine-camera to make such distinctions between cells, or to
identify cells with certainty; far from it, and even in the above example,
the macrophage and the fibroblast could appear almost indistinguishable if quiescent. In any case, only the major classes of cells can be
distinguished by their movements; After several days in culture the
fibroblast from a blood-vessel wall could not easily be distinguished
in this way from a cell derived from periosteal tissue, or even from the
dermis or from heart muscle. In other words, there is a whole group
of cells (mechanocytes), each with quite different functions in the body
(e.g. bone cells, tendon cells, fibroblasts, odontoblasts, plain muscle
cells, cardiac muscle cells, etc.), which may behave in much the same
way when they become isolated in a plasma clot, and their behaviour
then differs from that characteristic of several other large groups o f
cells, e.g. from epitheliocytes including epidermal cells, liver cells,
kidney cells, intestinal cells etc. or from amoebocytes, including
E . N . W I L L M E R
other hand, more vigorous cell movement immediately begins and the
extent and character of this movement (which is considered in detail
in Chapter 5) depends upon four things, at least. The age of the tissue,
the nature of the tissue, the nature of the substrate upon which the
movement takes place and the nature of the medium surrounding the
tissue are all of importance.
In using hanging-drop and slide-chamber cultures as a way of examining and studying cells, it is always helpful, and often essential for
diagnostic purposes, to make full use of micro-cinematographic
recording (see p. 40), in order to study cell movement. Single observations on cultures, or fixed and stained preparations of cultures
(see Fig. 1), are relatively useless for many of the problems that arise
in classifying cells which are constantly moving and changing. T w o men
standing on a hill-side may appear almost identical when seen from
a distance or in a still photograph; but as soon as they move or when a
cine-film of their movement is viewed, one, perhaps an insurance agent,
can be identified by his quick short step, and the other will be easily
recognized as the hill farmer by his long and loping stride. So it is with
cells. A macrophage emerging from an explant and creeping out between
a plasma clot and a glass surface sends out rounded pseudopodia,
lamelliform membranes or pseudopodia with "ruffles", and it moves
first this way and then that. An adjacent fibroblast, on the other hand,
glides outwards with what appears to be a more purposeful and directionally constant motion with only the leading edge frayed into ruffles.
As soon as it is possible to see and appreciate these movements, therefore, the distinction between the two classes of cell may become much
more obvious.
This does not, of course, mean that it is always possible even with the
help of the cine-camera to make such distinctions between cells, or to
identify cells with certainty; far from it, and even in the above example,
the macrophage and the fibroblast could appear almost indistinguishable if quiescent. In any case, only the major classes of cells can be
distinguished by their movements; After several days in culture the
fibroblast from a blood-vessel wall could not easily be distinguished
in this way from a cell derived from periosteal tissue, or even from the
dermis or from heart muscle. In other words, there is a whole group
of cells (mechanocytes), each with quite different functions in the body
(e.g. bone cells, tendon cells, fibroblasts, odontoblasts, plain muscle
cells, cardiac muscle cells, etc.), which may behave in much the same
way when they become isolated in a plasma clot, and their behaviour
then differs from that characteristic of several other large groups o f
cells, e.g. from epitheliocytes including epidermal cells, liver cells,
kidney cells, intestinal cells etc. or from amoebocytes, including