146 THE BEGINNINGS OF LIFE. 



this substance in which the cells are formed, cell- 

 germinating material (Zellenkeimstoff), or cytoblas- 

 tema. It may be figuratively, but only figuratively, 

 compared to the mother-lye from which crystals are 

 deposited.' 



The cells thus formed might remain isolated, or, 

 by the subsequent development and coalescence of their 

 walls in different ways, they might tend to produce 

 the various textures of the plant or animal. All the 

 tissues being thus either made up of cells variously 

 aggregated or derived by a metamorphic process from 

 cells, they maintained that ' the cause of nutrition and 

 growth resides, not in the organism as a whole, but in 

 the separate elementary parts the cells.' Schwann 

 believed that the c same process of development and 

 transformation of cells within a structureless substance 

 is repeated in the formation of all the organs of an 

 organism, as well as in the formation of new organ- 

 isms;' and he thought that the fundamental phenome- 

 non attending the exertion of productive power in 

 organic nature was always of this kind. 



Shortly afterwards Professor Goodsir 1 advanced the 

 doctrine that it was not so much the cells as the nuclei 

 of the textures which are the potential elementary parts 

 of the organism, and which therefore may be called 

 c centres of nutrition.' In a communication on this 

 subject he said : c The centre of nutrition with which 

 we are most familiar is that from which the whole 



1 ' Anatomical and Pathological Observations,' 1845. 



