182
M. A B E R C R O M B I E
strongly oriented that the assumption seems justified (Gaillard,
1936). But usually the value obtained has a most uncertain relation to
mean speed.
Intrinsic differences in speed between different cell types exist, the
most striking being between the "fixed" tissue cells and the white blood
cells. Absolute values vary so much according to circumstances that
they are not usually comparable between authors except in the most
general terms, but in most standard conditions of culture an avian or
mammalian fibroblast largely free of others may be expected to move at
speeds of roughly 50/x/h (Willmer, 1933; Willmer and Jacoby, 1936;
Abercrombie and Heaysman, 1953; Abercrombie and Gitlin, 1964).
Goodrich (1922) has recorded 360 /x/h for a fibroblast of Fundulus—an
exceptionally high speed. Schwann cells (Lubinska, 1961) and epithelia
move at speeds comparable to those of fibroblasts, and so do neurite
tips (Harrison recorded their speed in the first paper on tissue culture,
1907; see also Hughes, 1953). White blood cells, on the other hand, at
least lymphocytes and polymorphs during their periods of activity,
move the same distances in minutes rather than hours (Lewis, 1933;
De Bruyn, 1945). Macrophages, which are very difficult to measure
because of their extreme irregularity of course, seem to move somewhat
faster than fibroblasts, but considerably more slowly than lymphocytes
and polymorphs (Oldfield, 1963).
Within a population of cells of a given type a broad spectrum of
speeds will certainly be found. One cannot at present deny that this
variability is largely due to differences in the microclimate of each cell.
But some relatively autonomous fluctuations in speed of a single cell
have been described, and it seems probable that such variations, not
directly matched to environmental changes, are common. There are,
for instance, rather irregularly rhythmical changes in speed of locomotion of some mammalian lymph-node and bone-marrow cells in
vitro (Lewis and Webster, 1921; De Bruyn, 1945): rabbit lymphocytes
alternate a "depolarized" state of very slight movement lasting 20-400
sec with a "polarized" state of rapid movement (average 33/x/min)
lasting a similar time. Another instance of autonomous fluctuation is
the apparent correlation of speed of movement with the mitoticintermitotic cycle in fibroblasts. The post-mitotic cell, quite apart from
the brief spurt of speed as the daughter cells flatten out on a glass
surface, has a distinctly raised speed for some hours (Canti, 1928;
Abercrombie and Gitlin, 1964). These are temporal fluctuations of a
single cell. Whether there are cells with a consistently higher speed than
others, as in cellular slime moulds (Bonner, 1959), and, if there are,
whether the differences are inherited, as they are not in slime moulds,
remains to be seen.
M. A B E R C R O M B I E
strongly oriented that the assumption seems justified (Gaillard,
1936). But usually the value obtained has a most uncertain relation to
mean speed.
Intrinsic differences in speed between different cell types exist, the
most striking being between the "fixed" tissue cells and the white blood
cells. Absolute values vary so much according to circumstances that
they are not usually comparable between authors except in the most
general terms, but in most standard conditions of culture an avian or
mammalian fibroblast largely free of others may be expected to move at
speeds of roughly 50/x/h (Willmer, 1933; Willmer and Jacoby, 1936;
Abercrombie and Heaysman, 1953; Abercrombie and Gitlin, 1964).
Goodrich (1922) has recorded 360 /x/h for a fibroblast of Fundulus—an
exceptionally high speed. Schwann cells (Lubinska, 1961) and epithelia
move at speeds comparable to those of fibroblasts, and so do neurite
tips (Harrison recorded their speed in the first paper on tissue culture,
1907; see also Hughes, 1953). White blood cells, on the other hand, at
least lymphocytes and polymorphs during their periods of activity,
move the same distances in minutes rather than hours (Lewis, 1933;
De Bruyn, 1945). Macrophages, which are very difficult to measure
because of their extreme irregularity of course, seem to move somewhat
faster than fibroblasts, but considerably more slowly than lymphocytes
and polymorphs (Oldfield, 1963).
Within a population of cells of a given type a broad spectrum of
speeds will certainly be found. One cannot at present deny that this
variability is largely due to differences in the microclimate of each cell.
But some relatively autonomous fluctuations in speed of a single cell
have been described, and it seems probable that such variations, not
directly matched to environmental changes, are common. There are,
for instance, rather irregularly rhythmical changes in speed of locomotion of some mammalian lymph-node and bone-marrow cells in
vitro (Lewis and Webster, 1921; De Bruyn, 1945): rabbit lymphocytes
alternate a "depolarized" state of very slight movement lasting 20-400
sec with a "polarized" state of rapid movement (average 33/x/min)
lasting a similar time. Another instance of autonomous fluctuation is
the apparent correlation of speed of movement with the mitoticintermitotic cycle in fibroblasts. The post-mitotic cell, quite apart from
the brief spurt of speed as the daughter cells flatten out on a glass
surface, has a distinctly raised speed for some hours (Canti, 1928;
Abercrombie and Gitlin, 1964). These are temporal fluctuations of a
single cell. Whether there are cells with a consistently higher speed than
others, as in cellular slime moulds (Bonner, 1959), and, if there are,
whether the differences are inherited, as they are not in slime moulds,
remains to be seen.