Chapter IX 



TISSUE CULTURE AND THE STUDY OF 



PROBLEMS IN THE PATHOLOGY 



AND GENERAL PHYSIOLOGY 



OF PLANTS 



The history of any biological method covers, in 

 general, three phases which may or may not be 

 simultaneous. These are: the development and 

 perfection of basic techniques ; the application of 

 those techniques to already recognized problems ; 

 and the formulation of new and unforeseen appli- 

 cations. Harrison (1907, 131) began with the sec- 

 ond phase in this series, having before him a defi- 

 nite problem, the elucidation of the origin of nerve 

 fibrils, before he devised the tissue culture tech- 

 nique. Having solved that particular problem by 

 relatively simple methods, he found no further 

 incentive to perfect or expand the technique and 

 turned to other problems amenable to other tech- 

 niques. Carrel (1911 et seq., 120), on the other 

 hand, without a specific problem but with a less 

 formulated concept of a vast field of problems, 

 took this technique and perfected it to a very high 

 degree. The application to new but specific prob- 



