CHAPTER IV 



THE CELL AND THE ORGANISM 



Summary. — The cell is the second fundamental structure of the 

 universe. It is possible that both before and after the origin of 

 atoms and cells, as well as in between, other structures arose in the 

 course of cosmic Evolution. If so, they have passed away, and we 

 have now only these two permanent survivals which we can 

 scrutinize for clues as to the basic character of the universe. 



In the study of animate nature Evolution or Organic Descent has 

 till recently attracted most attention. But more recently the study 

 of the structure and functions of the cell has come rapidly to the 

 front and now probably forms the principal centre of interest in 

 JBiology. 



That all plants and animals consist of cells; that cells contain 

 certain peculiar bodies called nuclei ; that all higher organisms arise 

 from cell- fusions in which the nuclei play a prominent part — all 

 these facts have been discovered only in comparatively recent 

 years; and our knowledge of cells is therefore still in its earliest 

 stage. But Cytology is now, with much-improved methods and 

 appliances, making rapid strides, and great discoveries are confi- 

 dently looked forward to. 



Besides the nucleus the cell consists principally of a rapidly 

 circulating jelly-like fluid, enclosed in a more or less well-marked 

 wall or membrane of a permeable character ; and the fluid contains 

 numerous exceedingly complex chemical compounds in solution or 

 in the colloid state. The structure of a cell is therefore most com- 

 plex, and in fact comparatively little is yet definitely known about 

 it. Its functions are even more mysterious, for they include prac- 

 tically all the activities which we see in developed organisms — 

 birth, growth, breathing, feeding, digestion, self-healing, reproduc- 

 tion, and death. Its most distinctive function is metabolism, 

 which means that it thoroughly alters and transforms all food 

 materials before assimilating them ; that all its apparently physical 

 activities are of this transformative metabolic character instead of 

 being simple mechanical operations. It appears to form complex 

 chemical compounds, called enzymes, which in their colloid state 

 enable these distinctive radical transformations to be effected. 

 The apparently simple physical processes such as osmosis in the 



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