CHAPTER XXXII 



THE TECHNIQUES FOR THE CULTIVATION OF VERTEBRATE 



TISSUES IN VITRO * 



778. The technique of tissue culture provides a means whereby 

 the growth or the survival of tissues and cells may be observed in 

 an environment apart from that of the intact organism. The 

 behaviour of cell-types in mixed cultures and in pure strains in 

 response to changes in the medium and to external stimuli, the 

 interaction between cultures of different types of tissues growing 

 side by side in the same medium, and the potentialities of 

 embryonic rudiments and organs isolated from the influences of 

 the rest of the embryo, have all been extensively studied by this 

 technique of explantation. In 1907 Ross Harrison first demon- 

 strated the growth of nerve fibres in fragments of nervous tissues 

 explanted from frog embryos in adult frog lymph. More recently 

 the technique has been modified in the direction of standardising 

 the conditions favourable to the active growth of cultures over 

 extended periods of time. Much has still to be accomplished in 

 the control of the chemical composition of the media and of the 

 gaseous environment of tissue cultures. It is no longer a pheno- 

 menon to obtain some sort of growth from any embryonic or fa^tal 

 tissue, and as Fell {Brit. Journ. Radiol., viii, 1935, p. 27) has 

 emphasised, " it is a waste of time and money to take up tissue 

 culture merely for the sake of growing cells." 



When sufficient technique has been acquired for the successful 

 cultivation of simple embryonic tissues such as heart muscle 

 (fibroblasts), iris epithelium, intestinal epithelium, etc., over a 

 period of a month or more, attention should be given to the 

 problem of controlling the composition of the media, and the gases 

 in contact with it, as accurately as possible. The operation of 

 cutting out a fragment of living tissue and placing it in a nutrient 

 medium includes a wide range of possible errors and variable 

 results. To eliminate some of these variations in experimental 

 work, a large number of control cultures is desirable. The worker 

 should also be familiar with the appearance of degenerating cells 

 in vitro. Slight degrees of abnormality are often indicated only 

 by changes in the form of the mitochondria and other cytoplasmic 

 inclusions. At present the technique is largely dependent upon 

 personal skill and the quality of cultures is apt to vary considerably 

 in different laboratories engaged in tissue culture. 



* By K. C. R. 



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