5. T H E L O C O M O T O R Y B E H A V I O U R OF C E L L S
187
very striking. Harrison (1912) clearly recognized some of these effects.
If the substrate is in the form of oriented fibrils, separated by fluid
spaces, a cell, because of its requirement for a solid substrate, must move
along the fibrils. Harrison indeed seems to have chosen clotted lymph
as his original medium partly because its fibrils simulated those found
in fixed preparations of the embryo which, when not artefacts, he
suspected might guide outgrowing nerve fibers. Loeb and Fleisher
(1917) pointed out that even when the substrate took the form of a
meshwork, providing pathways in many directions, large fibrils would
nevertheless predominate in orienting the cell. They advanced the view
that tension is important in producing and orienting large fibrils in such
substrates. It has, however, been Weiss (1929, 1934, 1941) who has
shown how important orientation of cells by an oriented structure in the
substrate can be, who has given it its current name of "contact
guidance", and who has shown that there is probably more involved
than the mere necessity of a solid substrate for locomotion (the
"stereotropism" of Harrison and Loeb).
Data on the precise mechanism of this behaviour are lacking, since
the movement of individual cells does not seem to have been analysed,
but it is probable that the taxis, besides depending on a diminished rate
of turning when the cell is moving in the favoured orientation, at the
same time involves an increased speed. H o w the substrate exercises its
effect is also unclear. Under suitable circumstances there is no doubt
that the gross form of the solid substrate is operative, as Harrison, and
Loeb and Fleisher, supposed. But as Weiss early pointed out (1929;
though at this time he was interpreting the effects mainly in terms of
mitotic orientation) the ultramicroscopic structure of the substrate is
probably also effective; he later obtained evidence for this by culturing
on oriented collagen (Weiss and Taylor, 1956). Presumably the predominant orientation of the fine structure is in some way transferred to
the locomotory mechanism, perhaps via the surface structure of the cell
(see Weiss, 1961). Whatever the mechanism, there is one limitation of
substrate orientation as a director of cell movement. It does not in
practise polarize movement, but specifies equally two opposite directions. Which of these is chosen must depend on other behaviour patterns
(Weiss, 1958). In some cases the choice may be made by an intrinsic
polarity of the cell; some sarcoma cells give this impression
(Abercrombie, 1961b). In other cases, and particularly in the outgrowth
from an explant into an oriented plasma gel, contact inhibition (see
below) may decide.
A survey of different cell types to determine differences in the degree
to which they undergo contact guidance on a standard substrate has
yet to be made. Fibroblasts (Weiss, 1929), some sarcoma cells
187
very striking. Harrison (1912) clearly recognized some of these effects.
If the substrate is in the form of oriented fibrils, separated by fluid
spaces, a cell, because of its requirement for a solid substrate, must move
along the fibrils. Harrison indeed seems to have chosen clotted lymph
as his original medium partly because its fibrils simulated those found
in fixed preparations of the embryo which, when not artefacts, he
suspected might guide outgrowing nerve fibers. Loeb and Fleisher
(1917) pointed out that even when the substrate took the form of a
meshwork, providing pathways in many directions, large fibrils would
nevertheless predominate in orienting the cell. They advanced the view
that tension is important in producing and orienting large fibrils in such
substrates. It has, however, been Weiss (1929, 1934, 1941) who has
shown how important orientation of cells by an oriented structure in the
substrate can be, who has given it its current name of "contact
guidance", and who has shown that there is probably more involved
than the mere necessity of a solid substrate for locomotion (the
"stereotropism" of Harrison and Loeb).
Data on the precise mechanism of this behaviour are lacking, since
the movement of individual cells does not seem to have been analysed,
but it is probable that the taxis, besides depending on a diminished rate
of turning when the cell is moving in the favoured orientation, at the
same time involves an increased speed. H o w the substrate exercises its
effect is also unclear. Under suitable circumstances there is no doubt
that the gross form of the solid substrate is operative, as Harrison, and
Loeb and Fleisher, supposed. But as Weiss early pointed out (1929;
though at this time he was interpreting the effects mainly in terms of
mitotic orientation) the ultramicroscopic structure of the substrate is
probably also effective; he later obtained evidence for this by culturing
on oriented collagen (Weiss and Taylor, 1956). Presumably the predominant orientation of the fine structure is in some way transferred to
the locomotory mechanism, perhaps via the surface structure of the cell
(see Weiss, 1961). Whatever the mechanism, there is one limitation of
substrate orientation as a director of cell movement. It does not in
practise polarize movement, but specifies equally two opposite directions. Which of these is chosen must depend on other behaviour patterns
(Weiss, 1958). In some cases the choice may be made by an intrinsic
polarity of the cell; some sarcoma cells give this impression
(Abercrombie, 1961b). In other cases, and particularly in the outgrowth
from an explant into an oriented plasma gel, contact inhibition (see
below) may decide.
A survey of different cell types to determine differences in the degree
to which they undergo contact guidance on a standard substrate has
yet to be made. Fibroblasts (Weiss, 1929), some sarcoma cells