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Chapter 6 

 GROWTH IN TISSUE CULTURE 



Chanty Waymouth 



The title of this chapter contains traps for the unwary, and it is well to examine 

 and avoid these. What is "tissue culture"? A tissue (L. texere, to weave) in the 

 histological sense, denotes an integrated assemblage of cells, the whole being a 

 recognizable entity with an architecture which makes it more than merely a 

 random aggregate of the component cells. Tissue culture (L. cultura, the original 

 feminine of the future participle o^ colere, to till), insofar as it is etymologically 

 related to "colony" (L. colonia, a band of husbandmen), perhaps connotes a means 

 whereby, with skilful husbandry, a crop can be harvested from a tissue. The crop, 

 of course, is cells. By general standards of good husbandry, it is to be expected that 

 the harvest will be greater than the seed. And so the idea of "growth", in the sense 

 of producing a crop appears to be implicit in the term "tissue culture". The traps 

 are three. One is that, as it is practiced, tissue culture often involves the use of 

 cells not integrated in the histological sense — that is, the technique covers a broader 

 field than this, and is in reality a method for studying populations of cells. Second- 

 ly, the methods of tissue culture do not invariably result in an increased crop of 

 cells. The colony studied may decline in numbers; it may survive; differentiation 

 may occur; it may remain stable by reaching an equilibrium between cell death 

 and cell proliferation; or, the colony may indeed increase. For the purpose of 

 compiling their comprehensive bibliography of research in tissue culture, Murray 

 and Kopech (1953) adopted the definition of tissue culture as "the maintenance 

 of isolated portions of multicellular organisms in artificial containers outside the 

 individual for considerable periods of time". This is the current usage. The third 

 trap lies in the term "growth". In a volume devoted to this topic, it may be out of 

 place here to labour the fact that "growth" is a hydra-headed monster. Let it 

 suffice to say that increases of various kinds — in number, length, volume, mass, 

 surface area — are comprised in this term, and that every use of the word should 

 be examined, to find out which manifestation or combination of manifestations is 

 alluded to in the case in point. 



Tissue culture is a valuable method for the study of populations of cells, organ- 

 ized or unorganized, away from the parent organism. Interactions of the cells 

 with each other and with the environment can be investigated and observed. It 

 must not be lost sight of that a tissue culture consists of more than the explanted 

 cells: the culture includes also the medium. Cells and medium form a system the 



