184 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



the egg cell. In some lower forms of life it has 

 been found by experimental biologists that the egg 

 may be stimulated to at least partial developmental 

 changes without action of the male sexual cell. 

 Thus Professor Loeb found that the egg of the sea 

 urchin develops into a larva when treated with 

 certain inorganic salts, in suitable concentration, 

 although here it cannot be claimed that these salts 

 contribute to the new being the hereditary qualities 

 which would have been given by the male cell. But 

 it is an open question whether the human egg cell 

 is capable of being stimulated to develop, even par- 

 tially, by means of any chemical agents which are 

 not laden with the materials that carry hereditary 

 traits. 



In man, as in all complex animal organisms, there 

 is a highly notable contrast between the cells in 

 process of active development and those that have 

 matured. An animal cell consists of two clearly 

 separated portions which have very different chemi- 

 cal compositions and biological properties the 

 centrally located portion known as the nucleus and 

 the surrounding mass of material which makes up 

 a large and often preponderant part of the cell 

 the cell body or protoplasm. What takes place in the 

 cell body is largely controlled and directed by the 

 cell nucleus, and damage to the nucleus compromises 

 the life of the entire cell, whereas the cell body may 

 be injured without necessarily affecting the integrity 

 of the nucleus. When the egg cell of a higher animal 



