178
M. A B E R C R O M B I E
techniques, all tend to encourage movement, which is then conveniently
available for observation and experiment. It is one of the major contributions of tissue culture that it opens the way to formulating a general
picture of locomotory behaviour and the factors influencing it; though
the application of knowledge gained in tissue culture to events within
the organism remains of course formidably difficult. It may be recalled
that Ross Harrison (1907) devised the technique for precisely the purpose of detecting and analysing an instance of cell locomotion presumed
to occur in the organism.
The present review will consider first the locomotory behaviour of
individual cells, and will then attempt to interpret some of the locomotory phenomena that cells show when associated together.
I I . T H E I N D I V I D U A L C E L L
A. M E C H A N I S M OF M O V E M E N T
The form of locomotion with which we are concerned requires a
solid substrate, on which the cells move by a co-ordinated process of
adhesion and de-adhesion. (There is a large literature on adhesion of
cells to substrates, which will not be considered in this review: see L.
Weiss, 1960; Curtis, 1962.) Some cells can project pseudopodia through
liquid (Holtfreter, 1947; Gustafson and Wolpert, 1961) but they can
only cross a fluid-filled gap if they maintain contact with a solid substrate. The mechanism of this locomotion on a solid substrate is little
understood, and will not be extensively discussed here. A confusion of
views exists even for so large a cell as Amoeba, which has been studied
intensively for more than a century (Goldacre, 1961; Allen, 1961; for
earlier work see De Bruyn, 1947). Important papers on the locomotion
of metazoan cells include those of Faure-Fremiet (1929), Lewis (1931),
Holtfreter (1946) and Ambrose (1961).
Vertebrate fibroblasts will serve as an example. In their locomotion
on a plane surface they are led by a ruffled membrane, a thin border of
the cell which shows active waves of thickening (Ambrose, 1961), and
itself forms the termination of a broad or narrow projection from the
body of the cell which is often termed a pseudopodium. The undulations observed are on the free, not the substrate, side of the cell, and are
concerned in pinocytosis. The ruffled membrane however is intimately
correlated with the process of locomotion (Abercrombie, 1961a) and it
is in this region that the cell is most closely adherent to the substrate
(Goodrich, 1920; Chambers and Fell, 1931). A forward flow of cytoplasm, which is one of the most obvious features in the movement of
Amoeba, is not observed, except when a pseudopodium is growing. The
M. A B E R C R O M B I E
techniques, all tend to encourage movement, which is then conveniently
available for observation and experiment. It is one of the major contributions of tissue culture that it opens the way to formulating a general
picture of locomotory behaviour and the factors influencing it; though
the application of knowledge gained in tissue culture to events within
the organism remains of course formidably difficult. It may be recalled
that Ross Harrison (1907) devised the technique for precisely the purpose of detecting and analysing an instance of cell locomotion presumed
to occur in the organism.
The present review will consider first the locomotory behaviour of
individual cells, and will then attempt to interpret some of the locomotory phenomena that cells show when associated together.
I I . T H E I N D I V I D U A L C E L L
A. M E C H A N I S M OF M O V E M E N T
The form of locomotion with which we are concerned requires a
solid substrate, on which the cells move by a co-ordinated process of
adhesion and de-adhesion. (There is a large literature on adhesion of
cells to substrates, which will not be considered in this review: see L.
Weiss, 1960; Curtis, 1962.) Some cells can project pseudopodia through
liquid (Holtfreter, 1947; Gustafson and Wolpert, 1961) but they can
only cross a fluid-filled gap if they maintain contact with a solid substrate. The mechanism of this locomotion on a solid substrate is little
understood, and will not be extensively discussed here. A confusion of
views exists even for so large a cell as Amoeba, which has been studied
intensively for more than a century (Goldacre, 1961; Allen, 1961; for
earlier work see De Bruyn, 1947). Important papers on the locomotion
of metazoan cells include those of Faure-Fremiet (1929), Lewis (1931),
Holtfreter (1946) and Ambrose (1961).
Vertebrate fibroblasts will serve as an example. In their locomotion
on a plane surface they are led by a ruffled membrane, a thin border of
the cell which shows active waves of thickening (Ambrose, 1961), and
itself forms the termination of a broad or narrow projection from the
body of the cell which is often termed a pseudopodium. The undulations observed are on the free, not the substrate, side of the cell, and are
concerned in pinocytosis. The ruffled membrane however is intimately
correlated with the process of locomotion (Abercrombie, 1961a) and it
is in this region that the cell is most closely adherent to the substrate
(Goodrich, 1920; Chambers and Fell, 1931). A forward flow of cytoplasm, which is one of the most obvious features in the movement of
Amoeba, is not observed, except when a pseudopodium is growing. The