THE CELL 17 



discovery. Originally enunciated by Schwann and Cell-Theory 

 Schleiden in 1838-9, it was, as has been said, first 

 formally laid down as a principle by Virchow in 

 the work which revolutionised pathology and is 

 the foundation of all modern knowledge in that 

 subject. It was through this discovery that the 

 common plan of organisation of plants and animals 

 first became evident. It was through it also that 

 we have arrived at an understanding of the pro- 

 cesses of fertilisation and of development. It is 

 clear, therefore, as Wilson J says " that the key to 

 all ultimate biological problems must, in the last 

 analysis, be sought in the cell ". Von Bunge points 

 out that it is no simple exercise which we set our- 

 selves when we proceed to endeavour to unravel 

 its mysteries. " When," he says, " with the help of 

 scalpel and microscope, we have dissected the 

 organism to its last shred, when we are concerned 

 only with the single cell then the greatest riddle 

 still lies before us. The single cell, the formless 

 structureless microscopically small drop of pro- 

 toplasm it shows all the essential functions of 

 life : nourishment, growth, reproduction, motion, 

 sensation yes, even functions which at least com- 

 pensate for the ' sensorium,' the conscious life of 

 the higher animals." 



The cell is indeed a very small object of study. 

 1 Op. cit., p. 1. 



