234 THE PRESENT IMPORTANCE OF SCIENCE 



The exceptions to this cellular organization of protoplasm, 

 such as multinucleated cells, plasmodia, syncytia, and so 

 forth, can all be brought into alignment with the general 

 theory of nucleoplasmic and cytoplasmic materials. There 

 was a time in the history of biology when nothing of the sort 

 was known, and later a time when an hypothesis of the uni- 

 versal cellular organization of living matter was proposed on 

 a basis of limited observation. This working hypothesis 

 was at first debatable. But the increasing number of cases 

 in which cells were observed, soon led to the acceptance of 

 the cell-theory as an established generalization, which may 

 to-day be designated as a fact, since it is hypothetical only 

 when we assume, as is done in the erection of the cell-theory, 

 that all living things are constructed after this fashion, 

 whether we have examined them or not. Having studied 

 hundreds of thousands of animals and plants and found them 

 all composed of cells, the theory is that we shall continue 

 to find the familiar cellular organization as new organisms 

 are examined. The term cell-theory is, like the term theory 

 of gravitation, theoretical only when it is assumed that it 

 will hold good elsewhere, or when analysis is pushed further 

 and we theorize about underlying causes. No one disputes 

 the existence of cells, or the assumption that they will be 

 found as long as microscopes are used any more than he 

 disputes the universality of gravitation because of which it 

 is believed that stones fall when dropped from a height 

 whether it be in California or Japan or on the planet Mars. 

 There is, therefore, much common agreement regarding the 

 existence of cells, and the agreement extends to many details 

 of their structure and activity, as for example that all cells 

 contain chromatin and that all cells have arisen from pre- 

 existing cells. 



When it is said that the cell-theory meets with common 

 acceptance, we mean that a host of trained observers have 

 examined the microscopic structure of innumerable plant 

 and animal bodies and found them composed of cells. Hence, 



