THE CELL 3 



true that living cells are never hollow chambers, but are 

 filled in whole or in part by a colorless, viscid, semi-fluid 

 substance, protoplasm. Many cells are simply masses 

 of protoplasm lacking entirely any kind of an enclosing 

 wall. Lying within the protoplasm is a minute body of 

 spherical form which is the cell nucleus. These two, 

 the protoplasm and the nucleus, are of universal occur- 

 rence and are the essential components of a living cell. 



4. Is the cell the physiological unit ? A study of the 

 form and function of the cell leads to the inevitable 

 conclusion that in a very real sense the cell is the mor- 

 phological unit of the organism. In its physiological 

 relations to the cells of the body as a whole, however, 

 it is not to be regarded as an independent unit but rather 

 as a localized center of bodily activities. The individual 

 cell in a multicellular body is influenced, sometimes in 

 a marked degree, by the surrounding cells. The most 

 fundamental problem in growth and development of 

 animals is what and how much influence do the body- 

 cells of one group have over the cells of another group. 

 Is there a physiological connection between adjoining 

 cells? Can a group of cells forming a so-called system 

 like the reproductive system in the animal body be in- 

 fluenced by the soma or body-cells ? If influenced at all, 

 can such influence have any effect upon the germ plasm 

 in the nucleus of the germ-cell ? Is it probable that the 

 germ characters may be changed by these influences so 

 that the offspring of the parent bodies where these in- 

 fluences have been at work, will correspond in any way 

 to the changes occurring in the parent body? In other 

 words, are acquired habits transmitted ? It is to be re- 

 gretted that the microscopic study of the cell has thrown 

 little light upon this fundamental question. As indicated 



