46 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



his cells are depleted and some of them actually lost. 

 During his period of rest new cells are built up from 

 the ingested foods and thereby, practically, new tis- 

 sues are formed, giving the feeling of comfort and 

 increased vigor. The acquisition of new tissues is 

 an asset and should be encouraged. 



Pathological tumors are abnormal growths of nor- 

 mal tissues. In many of these tumors the cells 

 multiply rapidly by mitosis, resulting often in un- 

 equal division of the chromosomes, or chroma tin 

 loops, but whether this is a cause or a consequence 

 can be argued with equal force. We are unable to 

 produce these tumors experimentally, and, unfor- 

 tunately, we are often unable to stop their mul- 

 tiplication of cells. 



The surface of a sphere increases as the square of 

 its diameter, while the volume increases as the cube 

 of the diameter. As the cells depend upon their 

 surface area for the absorption of food and elimination 

 of waste, and as the volume increases at a greater 

 rate than the surface area, the reduction in size of a 

 cell becomes a necessity. 



Much significance is attached to the fact that 

 mitosis brings about an equal division of the chro- 

 matin or chromosomes. If for any reason an un- 

 equal division obtains, the cell becomes abnormal 

 and a monstrosity, with death, follows. Experi- 

 mentally this may be done with an egg cell, which, if 

 anesthetized, allows more than one spermatozoon to 

 enter, resulting in an unequal division of the female 

 pronucleus and an abnormal development. That 

 chromatin is the bearer of hereditary qualities is a 

 postulate based upon the observation that mitosis 



