100
C H A R I T Y W A Y M O U T H
attention to some of the principles used in constructing synthetic media,
and to survey the uses to which these media are being put.
It is particularly important, when we look at the construction and
use of synthetic media for cells, to keep constantly in mind the role
of the cells in modifying the system. The composition of a chemically
defined medium changes as soon as cells are put into it, and from that
moment it is defined no longer. Paul (1959) has discussed, with many
examples from his own and some from others' work, the cell and its
environment and the contributions of both to the metabolism and
composition of cell-culture systems. He stresses the need for defining
standard conditions for the study of specific functions. Where the conditions, though standardized, are by definition artificial, no "normal"
condition of cells in culture can be said to exist. Paul is among those
who have done very careful work to establish a (but not the) satisfactory
balance of components for the cultivation of cells, and he states with
welcome emphasis that "It is clear . . . that it may be fallacious to
attempt to define one particular set of circumstances as absolutely
optimal since, by virtue of adaptive mechanisms, cells may be able
to exhibit optimal activity in a variety of circumstances" (Paul, 1959).
A completely defined environment for cells includes, not only the
medium supplied to them, but also the gas-phase and the solid substrate (if any) to which the cells attach.
A. USE OF B A L A N C E D SALT SOLUTIONS
Among the ancestors of modern Tissue Culture media are, as already
mentioned, the saline solutions, designed by physiologists in the late
19th and early 20th centuries, for maintaining tissues and organs in
condition suitable for short experiments in vitro. The principal function
of these solutions was seen as maintenance of osmotic and ionic equilibrium. They were essentially simple replacements for blood, and were
constructed to reproduce the major ionic components of that fluid.
Improvements and modifications, made empirically as use suggested,
were introduced from time to time, so that the early simple saline
solutions of Ringer (1880-2, 1886) and Locke (1895, 1900) were joined,
but never wholly superseded, by more elaborate, better buffered, and
glucose-containing mixtures such as that of Tyrode (1910). Exponents
of the Tissue Culture technique have themselves contributed several
well-known salt solutions, e.g. Drew (1923, 1927-8), Pannett and
Compton (1924), Gey and Gey (1936), Earle (1943), Hanks (1948),
Hanks and Wallace (1949), and others.
The success of the early simple physiological salt mixtures for maintaining the welfare and function of isolated tissue encouraged those who
C H A R I T Y W A Y M O U T H
attention to some of the principles used in constructing synthetic media,
and to survey the uses to which these media are being put.
It is particularly important, when we look at the construction and
use of synthetic media for cells, to keep constantly in mind the role
of the cells in modifying the system. The composition of a chemically
defined medium changes as soon as cells are put into it, and from that
moment it is defined no longer. Paul (1959) has discussed, with many
examples from his own and some from others' work, the cell and its
environment and the contributions of both to the metabolism and
composition of cell-culture systems. He stresses the need for defining
standard conditions for the study of specific functions. Where the conditions, though standardized, are by definition artificial, no "normal"
condition of cells in culture can be said to exist. Paul is among those
who have done very careful work to establish a (but not the) satisfactory
balance of components for the cultivation of cells, and he states with
welcome emphasis that "It is clear . . . that it may be fallacious to
attempt to define one particular set of circumstances as absolutely
optimal since, by virtue of adaptive mechanisms, cells may be able
to exhibit optimal activity in a variety of circumstances" (Paul, 1959).
A completely defined environment for cells includes, not only the
medium supplied to them, but also the gas-phase and the solid substrate (if any) to which the cells attach.
A. USE OF B A L A N C E D SALT SOLUTIONS
Among the ancestors of modern Tissue Culture media are, as already
mentioned, the saline solutions, designed by physiologists in the late
19th and early 20th centuries, for maintaining tissues and organs in
condition suitable for short experiments in vitro. The principal function
of these solutions was seen as maintenance of osmotic and ionic equilibrium. They were essentially simple replacements for blood, and were
constructed to reproduce the major ionic components of that fluid.
Improvements and modifications, made empirically as use suggested,
were introduced from time to time, so that the early simple saline
solutions of Ringer (1880-2, 1886) and Locke (1895, 1900) were joined,
but never wholly superseded, by more elaborate, better buffered, and
glucose-containing mixtures such as that of Tyrode (1910). Exponents
of the Tissue Culture technique have themselves contributed several
well-known salt solutions, e.g. Drew (1923, 1927-8), Pannett and
Compton (1924), Gey and Gey (1936), Earle (1943), Hanks (1948),
Hanks and Wallace (1949), and others.
The success of the early simple physiological salt mixtures for maintaining the welfare and function of isolated tissue encouraged those who