THE UNIQUENESS OF THE INDIVIDUAL 



no mere dustbin. Herbivorous animals get some of their food 

 from the action of cellulose-spHtting bacteria within it. The 

 bacteria may, moreover, synthesize vitamins, which are ab- 

 sorbed directly or may be recovered by eating the droppings 

 themselves — a slap in the eye for Metchnikoffs theory. The 

 theory is dead, and nothing is to be gained by propping it up 

 into a sitting position.* 



In the first twenty years of this century, there began to 

 accumulate new empirical evidence concerning the ''immor- 

 tality'* of the ordinary non-reproductive cells of the body — 

 more exactly, the immortality of the cell-lineages to which, by 

 successive acts of fission, such cells may be ancestral. Leo Loeb 

 and later, more clearly, Jensen showed that several tumours 

 will grow indefinitely if handed on by grafting from one animal 

 to another. 1 It used to be possible to buy from the laboratories 

 of the Imperial Cancer Research Fund a rat bearing Jensen'*s 

 rat sarcoma. Its cells are lineal descendants of those which 

 Jensen first transplanted some forty years ago. The technique 

 of growing cells outside the body proved as much for the cells 

 of normal tissue. A strain of connective-tissue cells was started 

 by Carrel and Burrows in 1912.2 The first year's growth was 

 not enough to demonstrate the perpetuity of the cell lineage. 

 We are 'not justified', said Ross Harrison in 1913, 'in referring 

 to the cells as potentially immortal . . . until we are able to keep 

 the cellular elements alive in cultures for a period exceeding 

 the duration of life of the organism from which they are taken. 

 There is at present no reason to suppose that this cannot be 



1 A clear elementary account of this early work is to be found in W. H. 

 Woglom, Fifth Scientific Report of the Imperial Cancer Research Fund, 

 p. 43, London, 1912. 



2 There are quite a number of popular accounts of this work, e.g. in 

 A. Carrel, Man the Unknown, New York, 1935; L. du Nouy, Biological 

 Time, London, 1936. 



* [A comparatively recent paper on Metchnikoff's theory is that by 

 S. Orla-Jensen, E. Olsen and T. Geill, Journal of Gerontology, 4, p. 6, 1948.] 



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