102
C H A R I T Y W A Y M O U T H
treatment with enzymes or chelating agents (Merchant, Kahn and
Murphy, 1960). (See also pp. 52-3.)
B. E A R L Y A R T I F I C I A L M E D I A : T H E I M I T A T I V E A P P R O A C H
The thought which has perhaps most steadily and persistently
directed the development of synthetic media has been that of imitating,
as closely as possible, the natural, biological fluids (blood and interstitial fluid) which bathe the cells in situ. The "physiological salt
solutions", as we have seen, were devised on this imitative principle
as far as the ions, and sometimes glucose as a metabolic substrate, were
concerned. The studies of Vogelaar and Erlichman (1933, 1936,
1937) laid the foundation for the artificial (but not yet fully defined)
media of Baker (1936) for fibroblasts, epithelial cells and monocytes.
These media, and the later developments from them (Baker and Ebeling,
1938, 1939), contained some of the crude and newly discovered
vitamins, as well as hormones such as insulin and thyroxine. It is of
interest that, even in this early venture into the field of artificial media,
it was recognized that the different cell types have different nutritional
requirements. The work of Fischer (Fischer, 1941, 1948; Astrup,
Ehrensvard, Fischer and 0hlenschlager, 1947; Fischer, Astrup,
Ehrensvard and 0hlenschlager, 1948; Ehrensvard, Fischer and
Stjernholm, 1949), among others, was strongly conditioned by the
imitative principle, which was carried further and further, as more and
more biologically active substances were recognized and identified,
until highly complex artificial media were constructed, containing
(besides the basic ions and sugar) vitamins, coenzymes, enzymes,
hormones, steroids, fatty acids and known or supposed components for
synthesis, especially of proteins, nucleic acids and polysaccharides.
The imitative method proved fruitful for the evolution of successful
formulae. This, together with the substitution method, i.e. the gradual
replacement of biological components by chemically known substances
discovered or believed to be contained in them, have been the main
routes to the synthetic media in use today. A third method, the purely
empirical testing of compounds either not found in the biological
fluids, or found there in proportions quite different from those eventually adopted in synthetic media, has also played a part, particularly in
such work as has so far been done on the design of specialized media
for particular cells, tissues or organs.
C. S Y N T H E T I C M E D I A AS SUPPLEMENTS TO B I O L O G I C A L M E D I A
It is not possible to draw a clear line between the approach of
supplementing biological media with synthetic media, and that of
C H A R I T Y W A Y M O U T H
treatment with enzymes or chelating agents (Merchant, Kahn and
Murphy, 1960). (See also pp. 52-3.)
B. E A R L Y A R T I F I C I A L M E D I A : T H E I M I T A T I V E A P P R O A C H
The thought which has perhaps most steadily and persistently
directed the development of synthetic media has been that of imitating,
as closely as possible, the natural, biological fluids (blood and interstitial fluid) which bathe the cells in situ. The "physiological salt
solutions", as we have seen, were devised on this imitative principle
as far as the ions, and sometimes glucose as a metabolic substrate, were
concerned. The studies of Vogelaar and Erlichman (1933, 1936,
1937) laid the foundation for the artificial (but not yet fully defined)
media of Baker (1936) for fibroblasts, epithelial cells and monocytes.
These media, and the later developments from them (Baker and Ebeling,
1938, 1939), contained some of the crude and newly discovered
vitamins, as well as hormones such as insulin and thyroxine. It is of
interest that, even in this early venture into the field of artificial media,
it was recognized that the different cell types have different nutritional
requirements. The work of Fischer (Fischer, 1941, 1948; Astrup,
Ehrensvard, Fischer and 0hlenschlager, 1947; Fischer, Astrup,
Ehrensvard and 0hlenschlager, 1948; Ehrensvard, Fischer and
Stjernholm, 1949), among others, was strongly conditioned by the
imitative principle, which was carried further and further, as more and
more biologically active substances were recognized and identified,
until highly complex artificial media were constructed, containing
(besides the basic ions and sugar) vitamins, coenzymes, enzymes,
hormones, steroids, fatty acids and known or supposed components for
synthesis, especially of proteins, nucleic acids and polysaccharides.
The imitative method proved fruitful for the evolution of successful
formulae. This, together with the substitution method, i.e. the gradual
replacement of biological components by chemically known substances
discovered or believed to be contained in them, have been the main
routes to the synthetic media in use today. A third method, the purely
empirical testing of compounds either not found in the biological
fluids, or found there in proportions quite different from those eventually adopted in synthetic media, has also played a part, particularly in
such work as has so far been done on the design of specialized media
for particular cells, tissues or organs.
C. S Y N T H E T I C M E D I A AS SUPPLEMENTS TO B I O L O G I C A L M E D I A
It is not possible to draw a clear line between the approach of
supplementing biological media with synthetic media, and that of