248 EFFECTS OF SEXUAL REPRODUCTION. 



expressions all imply fixity or tendency to remain in the condition 

 which exists at any particular time. Thus, when an organ which 

 has for a long time been dormant, or only slightly exercised, is 

 suddenly exercised violently, the system responds by repairing the 

 waste caused by this violent exercise, but it cannot repair waste so 

 rapidly nor so completely as it can after the exercise has been con- 

 tinued for a considerable period of time. The result of this is that 

 the newly exercised organ becomes quickly fatigued, and cannot 

 continue the exercise more than a short time. After the system 

 has acquired the habit of repairing waste in a particular organ, 

 that organ may be exercised for a much longer period before 

 fatigue ensues. Also after the system has once acquired the habit 

 of repairing the organ, that habit, after being lost by temporary 

 disuse, is reacquired much more quickly than it was acquired in the 

 first place, and the length of time necessary for such a re-acquire- 

 ment is proportional to the length of the disuse. 



FUNCTIONAL CONDITION OF CELLS. 



We thus see that a germ cell is made up of material which is 

 in a functional condition represented by a series of repairs follow- 

 ing upon a series of cell divisions, the quality of each repair of 

 which is dependent upon the coincident repairs going on in the 

 body of the adult within whom the cell is housed. As the func- 

 tional condition of the organs of the adult is the result of a con- 

 tinuous but varying process of repair, it will be evident that the 

 functional condition of these organs is accurately duplicated by a 

 corresponding functional condition of the elements of these organs 

 in the germ cell. 



When conception takes place cell divisions result in an aggre- 

 gate of somatic cells in which cell growth is substituted for cell 



