GROWTH IN TISSUE CULTURE 547 



parts of which are mutually dependent. As with the organism, so with a tissue 

 culture, "Les conditions de la vie ne sont ni dans I'organisme ni dans le milieu 

 exterieur, mais dans les deux a la fois." (Bernard, 1865). The principal advantages 

 of tissue culture are two : ( i ) an advantage over fixed sections or smears, that the 

 cells can be examined in the living state; and (2) an advantage over in situ studies, 

 that, the cells being isolated from the parent organism, complicating factors 

 introduced by the numerous regulatory and secretory mechanisms of the host are 

 excluded. The environment can be controlled. 



For many years, and perhaps this phase has not wholly been outgrown, tissue 

 culture and its exponents were surrounded by a certain aura of fascination. 

 Partly this was traceable to the fact, so surprising to physiologists of 50 years ago, 

 that cells taken from their host could not only remain alive but could grow and 

 multiply. The wonderment of the achievement of potentially unlimited growth 

 by the excised part so enthralled many investigators that, not content with poten- 

 tial immortality of the cells, they have most commonly used maximum growth as a 

 principal criterion of success in tissue culture. The more neutral term "explan- 

 tation", introduced by Roux and also used by Oppel {cf. Craciun, 1931) was 

 swept away in the enthusiasm for perpetual proliferation. Tissue culture today 

 comprises what was originally understood by "explantation" (survival in vitro) 

 and "true" tissue culture (multiplication of cells). Lewis and Lewis (1924) were 

 freer than many workers in the tissue culture field of preoccupation with "growth" 

 per se. They stated that "the first factor which makes tissue culture possible is the 

 ability of cells to survive for varying lengths of time after they have been removed 

 from the organism" . . . "Tissue culture depends primarily upon two factors: (i) 

 the ability of the various types of cells to survive . . . and (2) the ability of the cells 

 to migrate away from the explant into positions where their behavior and struc- 

 ture can be observed under favorable conditions. A third factor, the multiplication 

 of cells, plays an important role in many investigations". From this it is evident 

 that multiplication was not considered an essential factor for success by these 

 authors. It should in fairness be said, however, that from the beginning there 

 were many who used the new technique for detailed observations of the behaviour 

 and structure of living cells. Tissue culture, with Harrison (1906-07; 1906-08), 

 and with the Lewises (Lewis and Lewis, 1924; Lewis, 1936) was a method making 

 possible for the first time exact descriptions of cells during life. Though Garleton 

 (1923) predicted that "the histological researches of the future will be based more 

 on the physiology and dynamics of the cell than on descriptive morphology", there 

 are still today histologists and cytologists whose familiarity with cells is based only 

 on fixed preparations. Concepts of the cell built up from such studies are some- 

 times hard to reconcile with the picture seen in the living cell, and it is still not 

 unknown for the observations made on living cells to be rejected in favour of the 

 more familiar static picture of textbook histology. 



The preoccupation with proliferation, to the neglect of other manifestations of 

 the living cells in vitro, can be partly attributed to fascination with growth as a 

 process, but also partly to the apparent ease with which "growth" could be 

 measured. The potentialities of the method for studies on metabolism, and on 

 persistence or differentiation of functions such as muscular contraction, ciliary 



Literature p. 581 



