306 The Outline of Science 



egg-cell a potential organism, when we come to think of it 

 dividing and re-dividing into cells so that the unified business of 

 life may be more effectively carried on by division of labour. As 

 one of the greatest of botanists said: It is not that the cells form 

 the plant ; it is rather that the plant makes the cells. 



The Microcosm of the Cell 



With a few exceptions, notably Aristotle, the early natur- 

 alists were content to study the outsides of animals; then came 

 the study of internal organs, like hearts and lungs ; Bichat marks 

 the deeper penetration to the tissues that make up the organs; 

 then came the recognition of the cells that compose the tissues; 

 finally there was the recognition of protoplasm which Huxley 

 called "the physical basis of life." It may be useful to place the 

 different levels of study in a clear scheme (see illustration 

 facing p. 305). 



The old picture of a cell was that of a little drop of living 

 matter with a kernel or nucleus, and sometimes with an enclosing 

 wall. But the revelations of the microscope have made this 

 picture obsolete. We have to think of a more or less unified 

 minute area of great chemical diversity, with complex particles 

 and unmixing droplets restlessly moving in a fluid. In the centre 

 of this whirlpool, with its flotsam of reserve-products and waste- 

 products, there floats the nucleus, a little world in itself. Inside 

 its membrane, through which materials are ever permeating out 

 and in, there are readily stainable nuclear bodies or "chromo- 

 somes," usually a definite number for each species. And each 

 "chromosome" is built up of bead-like "microsomes" strung on a 

 transparent ribbon. It begins to make one's head reel cell, 

 nucleus, chromosomes, microsomes ! But it is all fact. 



Inside the nucleus there may be a nucleolus or more than one, 

 and outside the nucleus there is a minute body called the centro- 

 some, which plays an important part in the division of the cell. 

 This is not nearly all, but it is enough to suggest how complex is 



